Spotty liver disease in poultry

What do we know about spotty liver disease (Campylobacter hepaticus) in poultry?

In 2019 the first infection of Campylobacter hepaticus responsible for spotty liver disease (SLD) has been proven in a flock of Dutch laying hens (Molenaar 2019). However, the disease is not only emerging in the Netherlands, a fact proven by the publication of several articles on this subject in the recent years. This news article provides you with the practical information available so far.


The disease has already been described over 60 years ago and was mainly seen in the USA, UK and Germany since then. It gained increased interest when the number of outbreaks increased, starting in Australia. It was noticed that the incidence increased in line with an increase in birds in kept free range and in barns, instead of in cages (Van et al. 2017a).

Crawshaw et al. published about the identification of a novel Campylobacter strain in 2015. They described the isolation, biochemical, structural and molecular characteristics of the bacterium, but did not determine a name yet (Crawshaw et al. 2015).

Van et al. later also identified the same unknown Campylobacter species causing spotty liver disease in commercial chickens in Australia. Phylogenetic analyses based on the 16S rRNA gene and the heat shock protein 60 (hsp60) gene sequences indicated that the strains formed a uniform cluster that was clearly distinct from recognized Campylobacter species. When the average nucleotide identity was calculated, the new strains had a 99% concordance, but showed less than 84% similarity with the nearest sequenced species. A similarity of less than 95% indicates that the bacteria are from a different species, so Van et al. then proposed Campylobacter (C.) hepaticus as new name for this bacterium (Van et al. 2016).

The same group later proved that this bacterium is much more invasive to LMH cells (a chicken liver cell line) than other Campylobacter species. Besides, they showed that SLD could be induced by infecting mature layers orally with C. hepaticus and that the bacterium could be isolated from the liver and bile of these animals. They hereby fulfilled the postulates of Koch and proved C. hepaticus is the causative agent of SLD (Van et al. 2017a).

The bacterium

The most important characteristics of C. hepaticus are (Van et al. 2016):

  • bacterial morphology:
    • S-shaped;
    • contains long flagella at both poles;
    • motile;
    • 3-0.4 μm wide and 1.0–1.2 μm long after 3 days of incubation on HBA (horse blood agar) in a microaerophilic atmosphere at 37 °C;
    • Gram-negative;
  • colony morphology:
    • wet;
    • cream colored;
    • convex or flat and spreading;
  • biochemical characteristics:
    • non-hemolytic;
    • catalase positive;
    • oxidase positive;
    • urease negative.

In figure 1 you can see the morphology of C. hepaticus (Van et al. 2016).

Figure 1 Transmission electron micrographs of Campylobacter hepaticus showing their long bipolar flagella and S-shaped morphology (Vans et al. 2016).

A whole genome sequence has also been performed on C. hepaticus. This confirmed that this bacterium is most closely related to C. jejuni and C. coli, but still a distinct group (Petrovska et al. 2017). The phylogenetic tree is shown in figure 2.

Figure 2 Relationships between C. hepaticus and other Campylobacter species based on gene-by-gene analyses (Petrovska et al. 2017).


SLD occurs mainly in laying hens in free range systems, but has also been found in laying and breeding hens in barns and cages (Molenaar 2019; Van et al. 2016).

It is expected that birds get SLD after they get infected via the fecal-oral route with C. hepaticus. The bacterium is present in the gastro-intestinal tract of infected birds, and viable bacteria can be isolated from chicken faeces (Phung et al. 2020; Van et al. 2017a; 2017b).

C. hepaticus DNA has been identified in wild birds, rats, mites and flies. It has also been shown in water and soil from infected farms. It is however unknown if these are also vectors for viable C. hepaticus organisms. This means that more research is needed to determine their possible role in transmission and introduction on the farm (Phung et al. 2020).

Australian research has showed that the moment of infection does not have to correlate with the moment of mortality or lesions found at necropsy. Chickens can be infected with C. hepaticus up to eight weeks before SLD manifests itself clinically. A case has been described were birds were already infected during rearing (week 12). This implicates that an infection with C. hepaticus is not enough to cause SLD, but that other predisposing factors should also be present. Proposed predisposing factors are liver metabolism during peak production or changes in the gastro-intestinal microbiota (Phung et al. 2020). More research is needed to determine these factors.

Infections occur mainly during peak production, but are not limited to this period. Besides, after the initial infection at the peak of lay, further outbreaks can occur in the same flock at later ages (Phung et al. 2020).

Clinical disease

Flocks are often affected during peak production, but this can occur all year round (Molenaar 2019; Phung et al. 2020).
Flocks with SLD have higher mortality with acute deaths (Molenaar 2019). The mortality can be increased with more than 1% per day (Van et al 2017a) and can reach up to 10% in total (Phung et al. 2020).
In some flocks the egg production is decreased, with maximum decreases of 25% (Molenaar 2019; Phung et al. 2020). Sick animals are not always observed, due to the rapid death of affected animals (Molenaar 2019).


The disease is characterized by a large amount of small grey / white necrotic foci in the liver (spotty liver), as can be seen in figure 3 (Molenaar 2019; Van et al. 2016).
From the inoculation trials done by Van et al., it can be concluded that chickens with SLD can recover and that the liver lesions will then also disappear of the course of a couple of weeks (Van et al. 2017a).

Figure 3 Pathology of two birds with SLD: photo A of a bird that died, photo B of a bird that was euthanized and then necropsied (Van et al. 2017a).


All C. hepaticus isolates described in literature have been isolated from liver or bile samples, where it can often be found as monoculture (Phung et al. 2020; Van et al. 2017).
C. hepaticus is also present in the gastro-intestinal tract, with increasing concentrations along the gastro-intestinal tract (duodenum < jejunum < ileum < cecum). Despite the fact that gastro-intestinal concentrations are higher than liver concentrations, isolation from the gastro-intestinal tract has so far not been described (Phung et al. 2020; Van et al. 2017).

Cultivation of C. hepaticus is very difficult and it will not be successful by using standard cultivation methods (Molenaar 2019). C. hepaticus grows on nutrient agar with blood, but most don’t grow on MacConkey or Karmali agar (Van et al. 2016).

A PCR is available to determine if samples contain C. hepaticus DNA (Van et al 2017b). The analyses of cloacal swabs with PCR seems to be a reliable method to determine if C. hepaticus is present in live birds (Van et al. 2017).


Several antibiotics can be used to treat Campylobacter infections. Tetracyclines are generally first choice antibiotics. In the literature oxytetracycline is reported as main treatment option for SLD in Australia, but plasmid-borne resistance has already been reported (Phung et al. 2020).
Macrolides can also be used, but due to the risk of resistance in zoonotic Campylobacter species on public health, these are considered second choice antibiotics.
Lastly, also fluoroquinolones can be used.


Since C. hepaticus DNA has been shown in several materials incl. rats and wild birds, biosecurity seems to be a very important preventive tool to prevent infection of a farm, and also to prevent spread between stables.

There is no registered vaccine available. The use of herd specific (autogenous) vaccines is possible, but more experience will be needed to evaluate the efficacy.

Due to the fact that C. hepaticus was only recently identified as causative agent, little information is known about other preventive measures, such as the use of certain feed ingredients. Research did however already show some promising results for the use of biochar (Wilson et al. 2019). More research is however needed before this can be put into practice.


The whole genome sequencing showed that it is most closely related to Campylobacter jejuni and C. coli, which are both zoonotic bacteria. The bacterium however has not been detected in humans. More information is needed before a conclusion can be drawn on the zoonotic potential of Campylobacter hepaticus (Crawshaw 2019; Petrovska et al. 2017).


With RIPAC-LABOR we have a partner who is specialized in the isolation and cultivation of bacterial pathogens. RIPAC-LABOR invested in the culturing method of C. hepaticus and can now say that they can cultivate and identify C. hepaticus with MALDI-TOF. RIPAC-LABOR can also perform a PCR to detect C. hepaticus DNA in tissues.

The laboratory of RIPAC-LABOR is also possible and allowed to produce herd specific vaccines against C. hepaticus.

In case of a flock of which you suspect they are infected with C. hepaticus, you can always contact our Technical Support department to discuss the possibilities and further steps.


  1. Crawshaw, T. (2019) A review of the novel thermophilic Campylobacter, Campylobacter hepaticus, a pathogen of poultry. Transboundary and Emerging Diseases 66(4): 1481-1492.
  2. Crawshaw, T., Chanter, J., Young, S.C.L., Cawthraw, S., Whatmore, A.M., Koylass, M.S., Vidal, A.B., Salugero, F.J., Irvine, R.M. (2015) Isolation of a novel thermophilic Campylobacter from cases of spotty liver disease in laying hens and experimental reproduction of infection and microscopic pathology. Veterinary microbiology 179 (3-4): 315-321.
  3. Molenaar, Robert Jan (2019) Nieuws uit de monitoring – Spotty Liver Disease. Tijdschrift voor Diergeneeskunde.
  4. Petrovska, L., Tang, Y., Jansen van Rensbrug, M.J., Cawthraw, S., Nunez, J., Sheppard, S.K., Ellis, R.J., Whatmore, A.M., Crawshaw, T.R., Irvine, R.M. (2017) Genome reduction for niche associated in Campylobacter hepaticus, a cause of spotty liver disease in poultry. Frontiers in cellular and infection microbiology 7: 354.
  5. Phung, C., Vezina, B., Anwar, A., Wilson, t., Scott, P.C., Moore, R.J., Van, T.T.H. (2020) Campylobacter hepaticus, the cause of spotty liver disease in chickens: transmission and routes of infection. Infection. Frontiers in Veterinary Science 6:505.
  6. Van T.T.H., Elshagmani E., Gor M.C., Scott P.C., Moore R.J. (2016) Campylobacter hepaticus nov., isolated from chickens with spotty liver disease. International Journal of Systematic and Evolutionary Microbiology 66, 4518–4524.
  7. Van T.T.H., Elshagmani, E., Gor, M.C., Anwar, A., Scott, P.C., Moore, R.J. (2017a) Induction of spotty liver disease in layer hens by infection with Campylobacter hepaticus. Veterinary Microbiology 199: 85-90.
  8. Van, T.T.H., Gor, M.C., Anwar, A., Scott, P.C., Moore, R.J. (2017b) Campylobacter hepaticus, the cause of spotty liver disease in chickens, is present throughout the small intestine and caeca of infected birds. Veterinary microbiology 207: 226-230.
  9. Willson, N. L., Van, T., Bhattarai, S. P., Courtice, J. M., McIntyre, J. R., Prasai, T. P., Moore, R. J., Walsh, K., & Stanley, D. (2019) Feed supplementation with biochar may reduce poultry pathogens, including Campylobacter hepaticus, the causative agent of Spotty Liver Disease. PloS one, 14(4) e0214471.

Fatty liver haemorrhagic syndrome in poultry

Fatty liver haemorrhagic syndrome (FLHS) is a syndrome found mainly in laying hens. It is characterized by a sudden mortality, a decrease in egg production and large amounts of fat in the liver found during necropsy. In this article we want to share an overview of the main information including some recently published information about FLHS from the University of Queensland.


FLHS is a multifactorial syndrome for which several risk factors have been described:

  • a surplus of energy intake;
  • temperature extremes;
  • peak production (oestradiol);
  • low amount of liver phospholipids;
  • inflammatory challenges;
  • limited hen movement.

A surplus of energy intake

A surplus of energy intake seems to be the most important factor. Some authors conclude that the source of energy is irrelevant, but others conclude that diets high in carbohydrates are more likely to cause FLHS than high fat diets. It is hypothesized that feeding birds diets high in carbohydrates and low in fat results in a high de novo fatty acid synthesis in the liver. During the novo fat synthesis, fatty acids are formed from carbohydrates. These fatty acids can subsequently be converted into triglycerides or other lipids. The de novo fat synthesis puts much pressure on the liver fat metabolism. Diets with a higher fat concentration reduce the need for de novo fatty acid synthesis. FLHS is seen more in obese chicken than in chickens with a normal or low bodyweight. It is not known if this can be explained by the surplus of energy intake, or that it has a direct influence.

Temperature extremes

Hot temperatures are a well-known risk factor; FLHS is more prevalent during summer months. Exposure to extreme cold can also be a risk factor relevant for backyard chicken.
The explanation for the increased incidence after exposure to heat or cold stress is not completely clear. It has been shown in fowls that heat stress can influence the lipid metabolism. Other hypothesise are a reduce in energy requirement when environmental temperatures increase or a decrease in animal movement, which is also described as predisposing factor in caged hens.

Peak production (oestradiol)

High producing laying hens are mainly affected during peak production, which can be explained by the role of oestradiol (oestrogen); hens with FLHS have a higher plasma oestradiol concentration than non-affected hens. Oestradiol administration has also been used to induce FLHS in laying hens, which was most successful in hens that were also given ad libitum feed.
Oestradiol stimulates the fat storage in the liver, to provide for the fat needed for yolk production.

Liver phospholipids

The amount of phospholipids in the liver is also considered important for the development of FLHS; the phospholipid concentration is lower in chicken with FLHS than in healthy chickens. Phospholipids have a lipotropic action and are thus important for the mobilization of fat from the liver. Besides, they are present in the cell membrane where they regulate the integrity and porosity of the membranes, protecting cells.

Inflammatory challenges

Shini and his study group found that the inflammatory response is a contributor to the pathogenesis of FLHS in chickens already experiencing fat infiltration in the liver (steatosis). His study group found a higher concentration of fibrinogen and leucocytes (heterophils and lymphocytes) in chickens which suffered from FLHS than in control groups. Also the mRNA expression of IL-1β and IL-6 was higher. These cytokines are known to be involved in the activation and promotion of leucocyte infiltrations at sites of injury. Inflammation was found to be local (hepatic) and systemic.
In these animals, FLHS was induced by oestrogen and LPS (lipopolysaccharide). LPS is a component of the outer membrane of gram negative bacteria, which were used induce an immune response.
In the study it appeared that LPS were the reason for transition of a simple steatosis to FLHS. In commercial conditions the inflammatory reaction causing this transition can be caused by other factors, including nutritional and environmental factors. To our knowledge, there are not yet any researchers which studied the effect of anti-inflammatory veterinary medicinal products on FLHS.

Limited hen movement

FLHS has a higher incidence in hens in (enriched) cages, due to the limited movement of hens.


Mycotoxins have also been thought to be related to FLHS, but this is considered questionable. At least for aflatoxin it is known that they cause other hepatic lesions.

Figure 1 Figure from Shini (2014) showing the effect of estrogen treatment in combination with restricted feed intake (ERF) or ad libitum feed intake (EAL) on the estradiol levels.

Figure 1 Figure from Shini (2014) showing the effect of estrogen treatment in combination with restricted feed intake (ERF) or ad libitum feed intake (EAL) on the estradiol levels.

Onset of disease

Even though problems are often encountered during the production peak, the onset of FLHS started already at an earlier stage. The first changes in the liver can already be observed at the onset of the reproductive period, and are related to the increase in synthesis of lipids and proteins destined for the egg yolk. However, no clinical signs are detected at this stage. The most profound changes occur at or after the peak of lay most probably induced by oestrogen persistence throughout the laying period.

Susceptibility of birds

Why are birds so susceptible to this condition? This can be explained by marked differences between birds and mammals.

  1. Birds have a poorly developed intestinal lymphatic system. Therefore, fatty acids are secreted directly into the portal blood system as very low density lipoproteins (VLDL, portomicrons). All these portomicrons will pass the liver, predisposing birds to fat deposition in the liver.
  2. White adipocytes in birds have limited capacity for lipogenesis, resulting in a higher pressure on the liver for this task.
  3. The lipid requirement for the egg yolk must be met by de novo synthesis of fat in the liver, because portomicrons will not be used by the ovaria. The intensive synthesis of yolk lipoproteins by the liver occurs faster than their mobilisation, resulting in an increase in liver size and lipid content. Additionally, the rate of clearance of VLDL by the ovarian follicles is not as fast as hepatic release, resulting in an increase in circulating triglycerides.

Backyard chicken

FLHS is not only important for commercial hens. It is also an important cause of non-infectious mortality in backyard chicken. Especially nutritionally over-conditioned hens are at risk for developing FLHS, particularly in the spring and summer months. The increase in production of eggs in the spring in combination with the high temperatures seem to the cause.


Flocks with FLHS problems are often characterized by a sudden increase in mortality despite good laying percentages. The mortality is seen mainly in hens which are in full production. The mortality is usually 3-5%, but higher mortality rates have been reported. Birds that are found dead can be pale, but usually did not show any other clinical symptoms.
In some cases, the mortality can be accompanied by a (sudden) decrease in egg production.
In live animals it is very difficult to distinguish affected from healthy hens, although some hens do develop pale combs.


Necropsy on the birds found dead often reveals abdomens filled with large blood cloths, arising from the liver. Several abnormalities can be found in the liver, including:

  • hepatomegaly;
  • engorgement of fat. Usually 50-60%, but up to 70% of the dry matter can exist of fat;
  • a different colour which has been described as yellow, pale or putty coloured;
  • friability of the liver tissue;
  • small hematomas in the liver parenchyma of both dead and alive and seemingly healthy birds. Previous haemorrhages are often found in the margins of the liver lobes.

Large amounts of fat are not only found in the liver, but also in the abdominal cavity around the viscera. The ovaries are often active, at least in the early stages of FLHS. When the syndrome persists, inactive ovaries can also be found.

Recovery of the liver parenchyma will result in fibrosis. This can also be observed in hens that have recovered from FLHS. Due to the fibrosis after recovery of the disease, clinical symptoms can also occur during repeated mild episodes of FLHS and build-up of fibrotic tissue in the liver.

Figure 2 Necropsy of a bird with FLHS ( Trott et al 2014)

How do the excessive amounts of fat in the liver result in sudden haemorrhage? It has been proposed that excessive fat may disrupt the architecture of the liver and result in weakening of the reticular framework and blood vessels. Another proposed mechanism is focal necrosis of hepatocytes leading to vascular injury. Excessive lipid peroxidation of unsaturated fatty acids in the liver may overwhelm the cell repair mechanisms and result in tissue damage.


Besides the clinical symptoms and pathology, there is little one can do to diagnose this disease. There are unfortunately no diagnostic tests available.
Because of the difficulty of recognizing FLSH and the absence of diagnostic tests, the syndrome is often overlooked.


As explained in the first paragraph, FLHS is a multifactorial syndrome. The key part of prevention depends on prevention of the above mentioned risk factors.

Phospholipids and choline

Phospholipids are structural lipids, they are structural elements of cells. Lecithin is the major phospholipid and is an integral part of the structure of lipoproteins and the microsomal membranes to join them and therefore plays an essential role in the formation of very low density lipoproteins (VLDLs) and thus for the transport of fat from the liver to other tissues. Lecithin deficiency is associated with an accumulation of fat in the liver and a decrease in the quantity of fat deposited in the egg yolk.

One of the main components of lecithin is choline (phosphatidylcholine). Choline is therefore important for the incorporation and mobilization of triglycerides present in the liver and called a lipotropic factor. Besides, it is important for the utilization of fat.

Choline supplementation in laying hens is associated with elevated serum VLDL levels and a reduction of cardiac, hepatic and abdominal fat. The combination of these functions result in the prevention of abnormal accumulation of fat in the hepatocytes, the so called “fatty liver”.

The requirement of choline increases with high-fat diets. The supplementation of choline can also be particularly interesting during periods of heat stress, since the deposition of fat in the liver increases significantly at higher temperatures.

Due to the severity of this syndrome, it is vital to act quickly. Complementary feeds which provide for example choline, are therefore preferentially given via the drinking water.

Dopharma has a complementary feeds with choline in combination with betaine, methionine, lysine, sorbitol and plant extracts. This liquid product Heparenol is very suitable for use in drinking water in poultry.

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  3. Crespo, R. (2020) Fatty liver hemorrhagic syndrome in poultry. Consulted February 5th
  4. Crespo, R., Shivaprasad, H.L. (2008) Developmental, metabolic, and other noninfectious disorders. Chapter 30 in Diseases of Poultry, 12th edition, Edited by Saif, Y.M.
  5. Dong, X.F., Zhai, Q.H., Tong, J.M. (2019) Dietary choline supplementation regulated lipid profiles of egg yolk, blood, and liver and improved hepatic redox status in laying hens. Poultry science 98: 3304-3312.
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  7. Griffith, M., Olinde, A.J., Schexnailder, R., Davenport, R.F., McKnight, W.F. (1969) Effect of choline, methionine and vitamin B12 on liver fat, egg production and egg weight in hens. Poultry science 48(6): 2160–2172.
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  11. Kahn, C.M. (2005) The Merck Veterinary Manual 9th Chapter Poultry – Fatty liver syndrome page 2226-2227.
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Necrotic enteritis and necro-haemorrhagic enteritis in broilers

Necrotic enteritis is a very important disease in broilers and turkeys, but is also found in layers and breeders. It is caused by toxins and enzymes produced by pathogenic strains of C. perfringens.
In the field, the disease is characterized by different clinical forms. A group of authors from the department of pathology, bacteriology and avian diseases of the faculty of veterinary medicine in Ghent (Belgium) recently published about the distinction of two clinical forms of necrotic enteritis (Goossens et al. 2020). In this article we will briefly present their conclusions.

Necrotic enteritis is characterized by necrosis of the small intestine. In 2019 we informed you about the toxinotypes of C. perfringens. The netB-producing toxinotype G was positioned as the most probable cause of necrotic enteritis in birds. You can find this article on our website.
There are however still research groups that isolate netB-negative toxinotype A strains from birds with this disease. When infecting other birds with these strains, they also develop disease, supporting that these strains are pathogenic. Re-isolation of these strains from the infected and diseased birds is however not reported. The postulates of Koch have therefore not yet been completely fulfilled.

Besides the fact that two different C. perfringens toxinotypes are isolated, there are two distinct presentations of disease on necropsy; a haemorrhagic and a non-haemorrhagic form, which are explained below.

Non-haemorrhagic necrotic enteritis

  • The non-haemorrhagic form is the best described and most commonly accepted form of necrotic enteritis.
  • This form also is often subclinical and associated with poor bird performance.
  • Lesions can be found mainly in the jejunum and ileum and are described as confluent mucosal necrosis, often covered by a pseudomembrane.
  • This form is caused by netB-positive toxinotype G strains.

Necro-haemorrhagic enteritis

  • The necro-haemorrhagic form of this disease is not so often described.
  • This form of necro-haemorrhagic enteritis is characterized by sudden death. Subclinical cases have not been described.
  • Lesions are also mainly found in the jejunum and ileum but in this case described as haemorrhagic; the mesentery is engorged with blood. When looking at the mucosa, the macroscopic lesions very much resemble those of non-haemorrhagic necrotic enteritis: confluent mucosal necrosis which is often covered by a pseudomembrane.
  • Necro-haemorrhagic enteritis seems to be linked with specific netB-negative perfringens type A strains. There is a resemblance with bovine necro-haemorrhagic enteritis which is caused by toxinotype A strains.

In the picture you can find the typical necropsy of a broiler with severe non-haemorrhagic (A) or necro-haemorrhagic (B) enteritis (Goossens et al. 2020).

Figure 1 Necropsy of a broiler with severe non-haemorrhagic (A) or necro-haemorrhagic (B) necrotic enteritis (Goossens et al. 2020)

Because of the confusion caused by the use of one single name for the description of these two syndromes, Goossens et al propose to rename the haemorrhagic disease entity to necro-haemorrhagic enteritis.


The different entities of necrotic enteritis can cause severe problems in farms. When treatment is indicated, it is advisable to use narrow spectrum antibiotics. As Dopharma we have the narrow spectrum penicillin Phenoxypen® WSP in our portfolio.

  1. Goossens, E., Dierick, E., Ducatelle, R., van Immerseel, F. (2020) Spotlight on avian pathology: untangling contradictory disease descriptions of necrotic enteritis and necro-haemorrhagic enteritis in broilers. Avian pathology DOI /10.1080/03079457.2020.1747593.

A heifer with diarrhoea at this time of year: have you checked for Paramphistomosis?

Parasitic infections are considered a significant and very common problem in relation to animal health, particularly for grazing ruminants. As veterinarians, when we refer to internal parasites we mainly think of gastro-intestinal worms, lung worms and liver flukes. We rarely, if ever, consider paramphistomatidae or rumen flukes. Nevertheless, these flatworms – that settle in the rumen of grazers (ruminants) – are found the world over. Where they previously primarily caused disease in ruminants in tropical and sub-tropical regions, it appears that infections in Western Europe are more common than we thought. Opinion is divided about the effect of these parasites on animal health and technical results.


Paramphistomosis, an infection caused by a parasite in the genus Paramphistomum, has been known for many years. Where paramphistomosis was previously described as a disease that occurred mainly in tropical regions, in recent years we have seen an increase in the prevalence in Western Europe too (Huson et al., 2017). Calicophoron daubneyi (formerly known as Paramphistomum daubneyi) is the most common of the various Paramphistomum species found in Europe. France, Great Britain, Ireland, Belgium, Portugal and Spain have seen a tremendous increase in the occurrence of this parasite and these countries emphasise the importance of control measures (Malrait et al., 2015). In the Netherlands, routine testing of all faeces samples received by the Animal Health Department in the period 2009-2014 revealed an incidence of 15.8% in cattle and 8% in sheep (H.W. Ploeger, 2017).

The spread through purchasing of infected animals across continents, improved diagnostic methods such as faeces inspection by a modified McMaster technique, climatological changes with increased rainfall and increased temperatures and switching to a more targeted treatment of liver fluke (not effective against rumen fluke) were all suggested as possible reasons for the increased prevalence. A recent study performed by Edinburgh University using the deep amplicon sequencing method revealed how extensive the impact of intense movements of animals is on the spread of the infection (Sargison et al., 2019). Based on this result, proper parasite control is required, in addition to preventative measures of course, such as combating the intermediate host through lowering the water level.

Life cycle

The life cycle of the rumen fluke Calicophoron daubneyi is very similar to that of the liver fluke Fasciola hepatica. In addition to having the same final host, the rumen fluke also has an indirect cycle, with the fresh water snail / mud snail Galba Truncatula acting as intermediate host (Kaufmann et al., 1996).

However, there are also clear differences between the two trematodes. Following ingestion of the infectious metacercaria by the final host, the excysted larvae are released in the abomasum from where they migrate to the duodenum. There they attach to the mucosa and continue to develop for 3 to 6 weeks. Their presence in and migration through the small intestines can cause significant amounts of damage. The immature stages can absorb large sections of intestinal wall, resulting in necrosis (Hendrix et al., 2006). Once the rumen fluke has fully matured, the parasite migrates back to the rumen and reticulum, where it attaches to the rumen papillae. After being present in the rumen and the reticulum for several weeks, the adult rumen fluke is able to start producing eggs. These eggs end up in the pasture via the faeces. Miracidia emerge from the eggs only in an aqueous environment and if the temperature is above 10 ˚C. These miracidia can survive for a maximum of 24 hours in the outside world. They spend this time searching for the intermediate host Galba Truncatula. After several developments in the intermediate host, the cercaria are excreted. The cercaria that are released undergo fairly rapid encystation to form metacercaria in a suitable location (such as a patch of grass near water). They can survive for up to 6 months in a temperate climate. The final host becomes infected when it eats the grass on which the metacercaria are present.


Life cycle of the rumen fluke, Calicophoron daubneyi (Huson et al., 2017)

life cycle paramphistomosis








We can distinguish between the symptoms in the final host caused by the immature stages on the one hand and the adult stages on the other hand.

Paramphistomosis can manifest in two ways in cattle:

Acute form caused by the immature stages

The migration of the juvenile rumen flukes and the migration in the mucosa of the small intestines can result in the destruction of the gastro-intestinal glands. Erosion of the intestinal epithelium, with haemorrhagic damage and mucosal oedema, becomes evident quite soon after infection with rumen fluke. The resulting acute haemorrhagic enteritis can be associated with significant diarrhoea, reduced appetite, dehydration, weight loss, anorexia and even death. Repeat infection of animals is often associated with type 1 hypersensitivity reactions, which can increase the severity of the symptoms.

Chronic form caused by adult stages

Relatively mild infestations of adult worms in the rumen rarely cause clinical symptoms.

However, large numbers of rumen flukes – preferably grouped near the ruminal folds – can cause tympanites, ruminal atrophy and oedema formation in the mucosal folds of the rumen. This can be associated with thinner faeces and reduced appetite.

Histopathological examination of infected cattle has revealed that a correlation exists between the number of rumen flukes and the damage to the rumen, such as hyperkeratosis and infiltration of inflammatory cells (Fuertes et al., 2015). However, it is not certain whether the presence of rumen flukes has a significant effect on the health, growth and performance of the final host. In contrast, a study at abattoir level found a clear negative association between rumen fluke infection and the carcass weight and the fat coverage of the animal (Bellet et al., 2016).

Building immunity

Most parasites induce a certain degree of immunity in their final host, resulting in a balance between the parasitic population and the host. It is not one hundred percent clear yet whether this phenomenon also applies to trematode infestations. According to Chauvin et al, 2012 this is not entirely the case for rumen fluke. Ferreras et al 2014 also suggest that repeated exposure to rumen flukes does not offer any protection against repeat infection. Repeated, severe infestations of rumen flukes can result in an accumulation of the number of rumen flukes.

In contrast, Knubben-Schweizer found in her research that successive small infections in older animals result in partial immunity.


Clinical symptoms are usually not very specific and therefore will not result in a clear diagnosis.

If the case history refers to animals with severe diarrhoea that graze in areas that are frequently flooded, then rumen fluke infection should certainly be taking into consideration when making the diagnosis.

Faeces inspection

At the moment, the presence of adult worms (egg-producing stage) can only be demonstrated by faeces inspection.

We can distinguish between qualitative and quantitative faeces examinations. Qualitative examination is usually sufficient for routine examinations. This is performed to check whether an animal is infected or not.

To obtain a clear impression of the degree of infection, it is better to perform a quantitative determination. The quantitative determination can include determination of the number of eggs per gram of faeces (=EPG) (Vercruysse, 1992). One of the quantitative methods used to determine the EPG of various types of parasites is the McMaster method. This method uses a counting chamber for this process. As the eggs of trematodes are relatively heavy, a flotation liquid with a specific gravity over 1.35 must be used.

Rieu et al. (2007) studied the degree of reliability of faeces testing for rumen fluke. A significant correlation was observed between EPG counts and the severity of the infection. Finding more than 100 eggs per gram of faeces was an indication that the rumen or reticulum contained more than 100 adult paramphistomatidae.

The Master’s thesis by Karen Malrait from the University of Ghent used a cut-off value of 200 EPG to distinguish a severe infection (more than 201 adult rumen flukes in the rumen) from milder infections. However, the amount of eggs in the faeces says nothing about the pathogenicity of the infection, as symptoms are primarily caused by the immature stages.

Faeces inspection during immature stages can yield a false negative result. This is due to the fact that immature stages do not excrete eggs. In severely infected animals, it is possible to detect red immature rumen flukes in the faeces.


Autopsy of dead animals can provide quite a lot of information.

For the acute form of the infection, the opening of the intestines will reveal the presence of red immature rumen flukes measuring one to two millimetres (depending on their stage of development), small superficial ulcers and oedema of the mucosa.

In the case of a chronic infection, opening of the rumen will reveal the adult parasites attached to the wall.

Research into serological and molecular techniques is ongoing and this may result in improved diagnostics in future.


As is the case with liver fluke infection, treatment is based on two pillars.


A sound pasture management plan, which ensures that cows are not left in marshy areas, is one of the most important things that can be implemented. Not allowing young, susceptible animals to graze with older animals, or not allowing young animals to graze during the most dangerous period of the pasture season can significantly reduce the infection pressure. Drastically reducing the survival chances of the fresh water snail by ensuring good drainage of pastures with a high water level will also significantly reduce rumen fluke infections.

Taking into account the information about the effect of the mass movement of infected animals on the spread of Calicophoron in the UK and Ireland (from the study performed under the supervision of Edinburgh University), it would seem sensible to treat infected animals too. Knowledge of the infection status of newly purchased animals is therefore certainly important.

But what to do with infected animals?

There are currently no anthelmintics registered in Europe for the treatment of rumen fluke infections.

Many in vitro and in vivo studies examined the efficacy of various de-worming agents to combat rumen fluke. No generally accepted criteria have been established to evaluate successful treatment with flukicides in the treatment of trematode infections. Therefore, as is the case with the treatment of nematode infections, we will also look at the reduction in the number of eggs present in the faeces.

A study by Arias et al., 2013 looked at the efficacy of albendazole, netobimin, closantel and oxyclozanide in the treatment of the rumen fluke Calicophoron daubneyi in naturally infected cows. Oxyclozanide and closantel, both administered orally, were deemed effective in this study.

The literature recommends oxyclozanide – registered for the treatment of liver fluke – as “the” molecule of choice for treatment of mature rumen fluke. The dosage of oxyclozanide used in the treatment of rumen fluke infections is higher than the registered dosage for liver fluke infections. Rolfe & Boray (1987) and Alzieu et al. (1999) studied the effect of various dosages of oxyclozanide on mature and immature rumen flukes.




The high dosage of 18.7 mg/kg twice, with three-day interval yields a good efficacy against both mature and immature stages. Side effects, such as diarrhoea and lethargy, have been reported in treated animals at such high doses. These side effects disappeared 24-48 hours after the treatment. For fear of the above-mentioned side effects, veterinarians in the field prefer to work with the dose of 10 mg/kg BW (without stop dose) twice with 3 days in between and this with good results.

As rumen fluke infection does not form an indication for the veterinary medicinal products containing oxyclozanide, the treatment of paramphistomosis with this active ingredient can only take place via the cascade. If dosages exceeding those listed in the package leaflet are used, then the veterinarian must prescribe a withdrawal period that is sufficiently long to ensure that products derived from the animal will not contain unwanted residues.


Although rumen fluke infection has been discussed extensively in the literature, we have observed that rumen fluke is diagnosed in practice, but that an infection with severe clinical symptoms in cows occurs only sporadically. A recent study has revealed that – in addition to changing weather conditions – the mass movement of positive animals is a major contributor to the increased prevalence in recent years. Treatment with a de-worming agent is only recommended if the faeces inspection warrants this. Unnecessary treatments can contribute to resistance. No products have been registered to date for the treatment of paramphistomosis. Oxyclozanide has been described in the literature as effective.


  1. M. Huson et al., Paramphistomosis of ruminants: An emerging parasitic disease in Europe. Trends in parasitology, 2017, volume 33, No 11.
  2. Malrait et al., Novel insights into the pathogenic importance, diagnosis and treatment of the rumen fluke in cattle. Veterinary parasitology, 2015, pages 134–139.
  3. W. Ploeger et al., Presence and species identity of rumen fluke in cattle and sheep in the Netherlands. Veterinary pathology 243 (2017).
  4. Sargison et al., A high throughput deep amplicon sequencing method to show the emergence and spread of Calicophoron daubneyi rumen fluke infection in United Kingdom cattle herds. Veterinary parasitology, 2019, pages 9-15.
  5. Kaufmann et al., Parasitic infections of domestic animals, A diagnostic manual. Birkhäuse verlag, Basel 423 pp.
  6. Hendrix et al., Diagnostic parasitology for veterinarian technicians. Mosby Elsevier, Missouri, 2006, p 107.
  7. Huson et al., Paramphistomum of ruminants: an emerging parasitic disease in Europe. Trends in Parasitology, 2017, Vol. 33, N˚11.
  8. Devos et al., Paramphistomosis in sheep. Revue de médecine vétérinaire, 2013 164 (11): 528-535.
  9. Bellet et al., Ostertagia spp., rumen fluke and liver fluke single and poly-infections in cattle: An abattoir study of prevalence and production impacts in England and Wales. Preventive veterinary medicine, 2016, volume 132 pages 98-106.
  10. Chauvin, Trématodoses des ruminants. Le point vétérinaire, Parasitologie interne des ruminants, 2012, Vol 43, p 62-67.
  11. Ferreras et al., Calicophoron daubneyi in slaughtered cattle in Castilla y Léon. Veterinary Parasitology, 2014, Vol 199, p 268-271
  12. Knubben-Schweizer et al., Ein update zu pansenegeln in Deutschland, Hannover
  13. Fuertes et al., Pathological changes in cattle naturally infected by Calicophoron daubneyi adult flukes. Veterinary parasitology, 2015, volume 209 pages 188-196.
  14. Vercruysse, Parasitaire ziekten bij huisdieren. Deel I – Algemene inleiding. Cursus faculteit diergeneeskunde, 1992, page 10-13.
  15. Rieu et al., Reliability of coprological diagnosis of Paramphistomum spp. infections in cows. Veterinary parasitology, 2007, volume 146 pages 249-253.
  16. S. Arias et al., The efficacy of four anthelmintics against Calicophoron daubneyi in naturally infected cattle. Veterinary parasitology, 2013, volume 197 pages 126–129.
  17. Alzieu et al., Essai de traitement de la paramphistomose bovine par l’oxyclosanide. Méd.Vét., 1999, 150 (8-9), 715-718.
  18. Mage et al., Les paramphistomides; essai d’activité de quelques anthelminthiques. G.T.V., 1990, n˚4, 9-11.
  19. Dorchies et al., La paramphistomose bovine: une pathologie d’actualité. In: Comptes rendus du Congrès de la société française de buiatrie Paris, 15-17 novembre 2000, 132-142.
  20. Rolfe et al., Chemotherapy of paramphistomosis in cattle. Aust. Vet. J., 1987, 64, 328-332.

Distocur; don’t you also want to treat your dairy cattle against liver fluke during lactation and the entire non-lactating period?

Dairy farms that put their cows out to pasture or feed them fresh grass may be affected by liver fluke sooner or later. Liver fluke is gaining ground in Western Europe. More infections are being reported in the Netherlands and Belgium, too. Death caused by liver fluke is almost unheard of in cattle. Does that make this disease less important?

Liver fluke

Liver fluke infection or distomatosis is a parasitic disease in ruminants that is caused by trematodes or flatworms. The large liver fluke that is found in our neck of the woods is called Fasciola hepatica. This disease causes significant economic losses worldwide. The losses are attributed mainly to reduced milk production, weight loss and rejected livers in the abattoir. In addition, a liver fluke infection can amplify or reduce the effect of other pathogens or interfere with their diagnosis (see further in this text). What people also tend to forget is that this parasite can cause problems in other grazers and also in humans.

Liver fluke – prevalence and risk factors

Liver fluke infections used to occur only in countries further to the south, but in recent years we have seen increasing numbers of liver fluke infestations in our countries too. Changing climatological conditions (milder winters, high temperatures and more precipitation) have created better conditions for the development of the liver fluke. In addition, the changing weather conditions also mean that the period in which infection with liver fluke can occur starts earlier on in the pasture season. There are also other risk factors that facilitate the spread of liver fluke at a dairy farm. A study performed in Denmark revealed that heifers and non-lactating cows that graze in wet pastures form significant risk factors for persistence of a liver fluke infection at a dairy farm. Other factors include the purchasing of infected cows, no or poor treatment of infected young cattle and a lack of control over or occurrence of resistance. For example, resistance to triclabendazole can result in a steady spread of liver fluke infections.

Liver fluke – life cycle

The liver fluke has an indirect cycle, in which the pond snail Galba truncatula plays an important role as intermediate host. The presence of this pond snail is vital to completing the life cycle of the liver fluke.

The adult liver fluke lays eggs in the liver, which are excreted together with the bile in cattle dung. An adult liver fluke can produce 4,000 to 7,000 eggs per day. Once excreted, ciliated larvae or miracidium larvae emerge from the eggs. These miracidia need to find a pond snail within 24 hours in order to survive. Once inside the snail, the larvae develop into cercariae. These larvae then leave the snail and this is how they reach the pastures. Once the tail is lost, the larva encapsulates to form a contagious cyst (metacercaria). Grazers can become infected when they eat these cysts via the grass. Juvenile liver flukes develop in the small intestine within hours of ingestion. These flukes drill their way through the intestinal wall and migrate through the abdominal cavity towards the liver and bile ducts.

In cattle, the life span of a liver fluke varies from 6 months to two years.

Liver fluke – symptoms

The migration of the parasite in the liver and the damage caused there can cause a whole range of symptoms. These can vary from reduced milk production, weight loss, reduced fertility and diarrhoea, to death.

Liver fluke life cycle








Figure 1 The liver fluke cycle in cattle with intermediate host Galba truncatula

An infection in cattle is often sub-clinical and therefore latent, resulting in economic consequences. In sheep the infection can result in sudden death, particularly in young animals.

Liver fluke – diagnosis

The liver fluke diagnosis can be made in various ways. Not every method is relevant at every stage of the infection.

Dung inspection

A dung inspection (sedimentation-flotation) can reveal the number of eggs excreted by adult worms. The dung (rectal sample) is examined under a microscope for the presence of liver fluke eggs. The presence of eggs from the parasite is inconclusive and cannot be performed at every stage. For example, during the prepatent period, the immature stages do not excrete eggs. Furthermore, the number of eggs found in the faeces does not always correlate to the number of adult parasites in the liver. After ingestion of a metacercaria, it takes on average 10 to 12 weeks for the liver fluke to mature and start excreting eggs. The best period for a dung inspection is 3 months after the end of the pasture season. Due to intermittent excretion, it is obviously best to sample several animals from a group. The detection of liver fluke eggs in the dung provides information about the infestation in the group.

Detecting antibodies in the blood

A liver fluke infestation causes antibodies to be formed in the blood. These antibodies can be detected in the blood using an ELISA test four weeks after contracting a liver fluke infection. The antibodies can be detected up to 180 days after an infection. This implies that an infection contracted in the autumn can still cause a positive test for antibodies in the blood in the following year. Therefore, this test cannot be used to detect an effective infection. Once antibodies have been detected, the blood can also be tested for liver enzyme concentrations of gamma glutamyl transferase (GGT) and glutamate dehydrogenase, to get an idea of the liver damage that has been caused.

Detecting antibodies in the milk

Tank milk testing can be used to determine the Optical Density Ratio (ODR) of antibodies targeted against Fasciola hepatica. This tank milk testing can be performed throughout the year, but should preferably be performed before the end of the pasture season. This gives the dairy farmer an idea of the extent of infection at a farm-wide level. An ODR < 0.30 is considered negative. An ODR between 0.30 and 0.50 points to a liver fluke infestation without severe production losses. An ODR > 0.50 points to a severe infestation of liver fluke with potentially negative effects on milk production and fertility.

Detecting antigens in the dung

An ELISA test to detect antigens in the dung (high sensitivity) can be used to check how severely an animal is infected.


Animals that have died can also be examined to check how badly the liver is damaged.

Liver fluke – development of immunity

The immune response as a reaction to the presence of pathogens can be divided into a non-specific immune response and an acquired immune response. As the term suggests, the non-specific immune response is not specific to a certain pathogen and therefore does not result in an immunological memory. In the acquired or adaptive immune response, the B-cells that can differentiate into antibody-secreting plasma cells and the T-cells that can differentiate into CD8+ cytotoxic T-cells, CD4+ helper T-cells and regulatory T-cells are important. A lot is known about the T-helper cells type 1 (Th1 cell) and type 2 (Th2 cell). The Th1 cell primarily produces IFN-γ and is important for the activation of macrophages, for the removal of intracellular pathogens and for cellular immunity. The Th2 cell primarily produces IL-4 and is important for the activation and recruitment of inflammatory cells and for humoral immunity.

Infections of Fasciola hepatica are associated with the release of high concentrations of Interleukin 4 (IL-4), IL-5 and IL-13, which ultimately results in elevated concentrations of IgE, eosinophilia and other immune responses associated with the Th2 subtype. The early differentiation between the Th1 and Th2 cell lines of the helper T-cells is facilitated by cytokines such as IL-4 and IFN-γ. The high concentration of IL-4 after liver fluke infection and the subsequent strong Th2 immune response also results in a down-regulated initial Th1 immune response with reduced IFN-γ production and reduced reactivity of the lymphocytes.

A schematic representation of the immune response regulation induced against Fasciola hepatica is provided below.

Liver fluke – immunomodulatory properties

Worms have developed various mechanisms to escape the host’s immune response. Maizels et al. referred to them as “The masters of immunomodulation”.

These immunomodulatory properties ensure that the worms can survive in the host and can cause interactions with inflammatory and immune mechanisms that are involved in other infections, vaccinations, allergic reactions or auto-immune diseases.

Some examples:

Bovine tuberculosis

Bovine tuberculosis (BTB) in cows caused by Mycobacterium bovis is still a major disease worldwide. The eradication programmes in most countries are based on:

  • SICCT (single intradermal comparative cervical tuberculin test)
  • IFN-ϒ blood test (secondary test).

As mentioned above, a liver fluke infection suppresses the Th1 immune response and therefore the cellular immunity. This may reduce the sensitivity of the two screening tests used in the field, resulting in false negative results.

This possible link was demonstrated by Robin J. Flynn of Dublin University.

In order to study possible interference, he vaccinated animals with and without liver fluke infection with the BCG vaccine (avirulent strain used in human medicine).

The SCITT and IFN-y test performed in the various groups of animals produced the following results:

Table: Results from SCITT and IFN-y test performed in the various groups of animals





The experiment described above revealed that in cattle infected with liver fluke interference can occur in the existing screening tests for BTB used in the field.

Excessive IL-4 secretion caused by liver fluke infection is primarily responsible for suppression of Th1 cellular immunity that develops after vaccination with Mycobacterium bovis.

The liver fluke with its immunomodulatory properties can increase the host’s susceptibility to infections by other pathogens. This is because the down-regulatory effect of IL-4 on the Th1 immune response (which is related to cellular immunity) can cause certain infections in which this type of immunity is important to be more severe.

Salmonella dublin

Studies performed in the late 1970s and early 1980s found that co-infection of cattle with Salmonella dublin and Fasciola hepatica resulted in increased severity of the clinical disease, a longer period of illness and an increased risk of co-infected animals becoming carriers of S. dublin. The pro-inflammatory response to Salmonella infection suppressed by F. hepatica ensures that the sensitivity to this intracellular parasite increases.

Escherichia coli O157

Escherichia coli O157 is a bacterium that is responsible for haemorrhagic diarrhoea in humans. Cattle are reservoirs for these verocytotoxigenic E. coli and therefore form a potential danger of transmission to humans. A study performed by the University of Liverpool revealed that cattle infected with Fasciola hepatica had an increased risk of excretion of E. coli O157. Proper management of distomatosis can prevent potential infection with E. coli O157.

Liver fluke – prevention and treatment

Combating the liver fluke is a two-pronged approach.


A good pasture management plan and a considered approach to moving animals to pasture can go a long way towards combating the liver fluke. A modified pasture management plan significantly reduces the contact between the final host and the infectious liver fluke stages.


Various flukicides are available on the Dutch market. Not all products are effective against every stage of the liver fluke. Triclabendazole, which is effective against all stages of the liver fluke, was for many years the product of choice in combating an infection. The problem is that the liver fluke is increasingly becoming resistant to this product. In addition, triclabendazole cannot be used for milk-producing cattle. Products containing oxyclozanide can be used in dairy cattle during lactation and the entire non-lactating period and are effective against adult liver flukes. Dopharma recently introduced Distocur 34 mg/mL, containing the active ingredient oxyclozanide, to its product range. Therefore, the treatment of a liver fluke infection or distomatosis in dairy cattle can now also be treated in the Netherlands without implementation of the cascade.


  • A.A. Rana et al, Fascioliasis in cattle – A review. The Journal of Animal & Plant Sciences, 24(3):2014, Pages: 668-675
  • J. Beesley et al, Fasciola and Fasciolosis in ruminants in Europe: Identifying research needs. Transboundary and Emerging Diseases, 65 (Suppl. 1):2018, Pages: 199-216
  • J.L. Williams, Liver fluke – an overview for practitioners.
  • Takeuchi-Storm et al, Patterns of Fasciola hepatica infection in Danish dairy cattle: implications for on-farm control of the parasite based on different diagnostic methods. Parasites & Vectors, 2018, 11:674
  • Focus op Leverbot, Praktische handleiding. [Focus on liver flukes, a practical guideline] DGZ – Ugent
  • Moreau and Alain Chauvin, Immunity against Helminths: Interactions with the Host and het incurrent infections. Journal of Biomedicine and Biotechnology, Volume 2010, Article ID 428593, 9 pages
  • J. Flynn et al, Experimental Fasciola hepatica infection alters responses to tests used for diagnosis of bovine tuberculosis. Infection and immunity, Mar. 2007, Pages: 1373-1381
  • M. Aitken et al, Effects of experimental Salmonella dublin infection in cattle given Fasciola hepatica thirteen weeks previously. Journal of Comparative Pathology Volume 88, Issue1, January 1978, Pages: 75-84
  • K. Howell et al, Co-infection with Fasciola hepatica may increase the risk of Escherichia coli O157 shedding in British cattle destined for the food chain. Prevetmed, 2017

Is our meat safe for consumption?

Most people consume products of animal origin such as meat, fish, eggs, milk (or dairy products like cheese or yoghurt) and honey. These products are a healthy part of our diet. Every now and then there are however incidents where safety of these products is up for debate, for example the problems with fipronil in eggs. In Europe a lot of measures are taken to guarantee the quality and safety of our food, including product of animal origin.

In this article we explain which precautionary measures are taken to make sure that everybody will be able to enjoy these products.

Acceptable Daily Intake (ADI)

Substances that are not naturally present in our food, such as feed additives and components used in veterinary medicines, have an Acceptable Daily Intake (ADI). This is the maximum amount of a substance that you can consume during your life without negative effects on your health. An ADI will only be determined when it is proven that a substance is not carcinogenic. Substances that may have a carcinogenic effect are not allowed to be used in the food chain and therefore do not get an ADI.

The ADI is usually determined through animal tests. The animals used for testing receive different doses of the substances to determine the highest concentration at which no negative effects are encountered (NOAEL: No Observed Adverse Effect Level). When several NOAELs are determined for the same substance, the lowest NOAEL is always used, unless it can be justified that another NOAEL is more appropriate.

The NOAEL is however not just taken on as ADI; two uncertainty factors are incorporated. The first factor is to compensate for possible differences between toxicity in the animals used for these tests and humans. The second factor compensates for the fact that some substances may be more toxic for specific risk groups such as elderly people, pregnant women, babies and children.

Often uncertainty  factors of 10 are used and the NOAEL is thus multiplied by 100 (NOAEL x 10 x 10). For certain risk factors a higher uncertainty  factor (such as 1000) is used.

Maximum residue limit (MRL)

MRL stands for Maximum Residue Limit. The MRL is important for food safety, because food of animal origin should not contain any residues in concentrations higher than the MRL.
A MRL is specifically determined for one active ingredient and should be determined for all pharmacologically active substances in veterinary medicines and biocides that are used in food-producing animals.

The ADI is taken as initial value for the determination of the MRL. The ADI is extrapolated using the intake of different foods according to a standard food package , or diet. This provides an overview of the food quantities that an average person will consume in one day. The standard food package is shown in the table below.

Table 1 Standard Food package for the determination of the MRL

Mammals Muscle 300 gram
Fat 50 gram
Liver 100 gram
Kidney 50 gram
Poultry Muscle 300 gram
Fat & skin 90 gram
Liver 100 gram
Kidney 10 gram
Fish Muscle & skin 300 gram
Milk 1500 gram
Eggs 100 gram
Honey 20 gram

The MRL should be determined in such a way that the exposure to the consumer is below the ADI. A lifelong exposure and ways other possible routes of exposure to the consumer of the same substance are taken into account here. When a substance for example is used in veterinary medicines, as well as in crop protection products, only 45% of the ADI may be used in the determination of the MRL for the use of this substance for veterinary use.

An overview of all determined MRLs can be found in table 1 of the Annex of Commission regulation (EU) 37/2010.

Risk assessment

The European Commission approves an application for the determination of a MRL and the level thereof on the basis of a scientific risk assessment by the CVMP (Committee for Medicinal Products for Veterinary Use, European Medicines Agency).

Amongst others, the results of the studies of the ADI and residue studies are taken in account. The risk of toxicological, pharmacological and microbiological effects on humans is taken into account as well. In addition, the pharmacological properties of the substance in the relevant animal species are examined. For substances that are used in food-producing animals, long-term exposure, possible effects on fertility in multiple generations and effects on pregnant animals, the embryo and the foetus are examined as well.

One of the things that is investigated, is the effect of a substance on the human intestinal flora. An assessment is made to determine whether the colonisation barrier could be disturbed. This barrier is formed by the normal intestinal flora and limits the invasion of exogenous micro-organisms and overgrowth of potentially pathogenic micro-organisms. It is also determined whether there is an increase in resistant bacteria.

Besides the characteristics of the substances and residues, the situation regarding the intended use of the substance is examined as well. This is done through a recommendation on risk management , including for example the following factors:

  • the availability of an alternative substance for the treatment of the animal species concerned;
  • the necessity of the substance to prevent unnecessary animal suffering;
  • consequences for the health of the people treating the animals.

No MRL required

Is an MRL always needed? No, there are exceptions. In some cases it is decided that residues in food are not dangerous for the consumer and because of this a MRL is not required. For example the use of vitamins of those it is known that they don’t have adverse effects, but are essential for humans and animals (for example biotin or folic acid).

A MRL is neither needed for substances that are pharmacologically inactive, which are only used only as excipient of preservative and are found to be safe. These substances then fall outside the scope  of the European MRL regulation.

Substances that are not allowed

Another exception occurs when it is concluded that the presence of a substance in food is undesirable, even if it is in low concentrations. This conclusion can for example be drawn when the presence of even very low concentrations pose a risk for human health. The substance will not get a MRL. Even when no definitive conclusion can be made on the consequences for human health, no MRL is determined. In such a case the substance is prohibited for use in food-producing animals. One example of such a substance is chloramphenicol. This substance is prohibited due to the possible risk on genotoxicity. This means that chloramphenicol possibly damages the genetic information in cells (the DNA), which could lead to mutations and eventually to the occurrence of cancer.

Withdrawal period

Finally, the MRL is implemented as the withdrawal period. This is the minimum period between the last administration of a veterinary medicine under normal conditions and the production of food derived from the animal. The objective of the withdrawal period is to make sure that there are no residues in food in concentrations that exceed the MRL.

For quick and easy access to the information , the withdrawal period is always mentioned on the Specific Product Characteristics (SPC) and on the package leaflet and/or packaging of the product.

Veterinary medicines for food-producing animals can only be registered when an ADI and MRL have been determined and it has been shown that the withdrawal period indicated is sufficient to prevent exceedances of the MRL in products of animal origin. This is shown in residue studies. In these studies the product is administered to healthy animals used for these test and the residues in tissues and other products of animal origin are determined at different time points after the last administration. The animals used in these tests are always of the same animal species as the animals for which the product will be registered.

Veterinary medicines are only allowed for use in food-producing animals when they are registered for the concerning animal species. This means that a withdrawal period is established for the given animal species.

Only to avoid unacceptable suffering in animals, a product that is not registered for the intended animal species and indication is allowed to be used (cascade). This is only allowed for substances for which a MRL is established (possibly in another animal species) or for which it is determined that no MRL is required. And of course there are rules to determine the minimal withdrawal period for the species in which the product is used.


All above mentioned studies have been executed before a veterinary medicine is registered. But does it mean that the measures stop as soon as the product is on the market? No! After the approval of the registration, several steps will be taken to ensure food safety too.

  • The farmer must keep a register with the administered veterinary medicines. This information is shared when the animals are slaughtered, in order for the slaughterhouse to be able to check whether the withdrawal period was respected.
  • The inspection body responsible carry out random checks of products from animal origin to test if any residues are present. In the Netherlands this is performed by the Dutch Food and Consumer Safety Authority (NVWA). They use a framework called National Plan Residues (NPR), based upon the European regulations, to carry out these inspections. In the Netherlands hardly any residues exceeding the MRL are found.
    The EFSA (European Food Safety Authority) annually reports a summary of the monitoring in the entire EU. In 2016 369 262 samples have been analysed for the presence of prohibited or permitted substances. 0.31% of the samples did not comply with the regulations. This corresponds with the results of previous years (0.25% – 0.37% in the last 10 years). A broad range of substances is evaluated: not only antimicrobial or antiparasitic products, but also minerals such as copper. The number of non-compliances per animal product group is shown in the table.
    When interpreting these data, it should be taken into account that the monitoring is aiming for detecting deviations. This means that the selection of samples is executed in such a way that predominantly high risk products are often selected for investigation. When the samples would be taken randomly, a lower percentage of deviations might be found.
  • When residues in concentrations higher than the MRL are found in food, despite respecting the withdrawal period, this has to be reported to the marketing authorization or medicine board in a country in relation to pharmacovigilance. Based on these reports, an assessment will be made to determine if the advised withdrawal period is (still) sufficient.
    When it appears that the withdrawal period may not be long enough to ensure that animal food products do not contain residues that could pose a health hazard to the consumer, the registration is suspended. Delivery of the veterinary medicine will be prohibited and the product will be withdrawn from the market.
    Only when the authorization holder can prove that the withdrawal period (or a modified withdrawal period) is sufficient to guarantee food safety, the registration will be re-approved.

Table 2 Results of the monitoring on EU level

Category of animal product Number of samples with residues above MRL % of total amount of samples tested
Beef meat 331 0.30%
Pork 295 0.25%
Goat- and sheep meat 82 0.49%
Horse meat 28 0.84%
Poultry meat 48 0.07%
Meat from farmed wild birds 17 1.06%
Meat form wild birds 165 6.69%
Rabbit meat 5 0.28%
Aquaculture 37 0.55%
Milk 38 0.16%
Eggs 44 0.35%
Honey 41 1.16%

Quality systems

Besides the regulations described above, there are some additional quality systems which ensure food safety of products of animal origin.

These quality systems often impose extra requirements, which are additional to the legal standards.


Although it can be concluded that the risk of exposure to a residue will never be zero, it can be concluded as well that many measures are taken to prevent residues from causing human health problems. In short these are:

  • always using the lowest NOAEL;
  • uncertainty factors of 100 to 1000 when determining the NOAEL;
  • safety margins when implementing the NOAEL to an MRL;
  • safety margins when implementing the MRL to a withdrawal period;
  • control systems by the government (national and European);
  • quality systems that provide extra supervision on the food safety of products of animal origin.

Besides, a risk on a possible negative effect is always taken very seriously when assessing the ADI, NOAEL, MRL and withdrawal period. Food safety is always the most important factor.


  1. Commission regulation (EU) 2018/782 of 29 May 2018 establishing the methodological principles for the risk assessment and risk management recommendations referred to in Regulation (EC) No 470/2009.
  2. Commission regulation (EU) 37/2010 of 22 December 2009 on pharmacologically active substances and their classification regarding maximum residue limits in foodstuffs of animal origin.
  3. Directive 2001/82/EG of the European Parliament and of the Council of 6 November 2001 on the Community code relating to veterinary medicinal products.
  4. EFSA Report for 2016 on the results from the monitoring of veterinary medicinal product residues and other substances in live animals and animal products.
  5. EFSA Scientific opinion on Chloramphenicol in food and feed.
  6. EMA Substances considered as not falling within the scope of Regulation (EC) No. 470/2009, with regard to residues of veterinary medicinal products in foodstuffs of animal origin.
  7. EMA Veterinary regulatory – Maximum residu limits (MRL).
  8. Regulation (EU) 2019/6 of the European Parliament and of the Council of 11 December 2018 on veterinary medicinal products and repealing Directive 2001/82/EC.
  9. Regulation (EU) 470/2009 of the European Parliament and of the Council of 6 May 2009 laying down Community procedures for the establishment of residue limits of pharmacologically active substances in foodstuffs of animal origin.
  10. Van der Merwe, D., Beusekom, C., van den Berg, M., Gehring, R. (2019) Fipronil en de volksgezondheid – Een toxicologisch perspectief. Tijdschrift voor Diergeneeskunde, Jan 2019.
  11. Voedingscentrum – Aanvaardbare dagelijkse inname (ADI).
  12. Voedingscentrum – Antibiotica.

Gastric ulcers in horses; ECEIM consensus statement

In 2015 the “European College of Equine Internal Medicine (ECEIM)” published the new “consensus statement” regarding gastric ulcers in adult horses.

This “consensus statement” is written by B.W. Sykes, M. Hewetson, R.J. Hepburn, N. Luthersson and Y. Tamzali. It was published in the “Journal of Veterinary Internal Medicine” (29: 1288-1299) and available as “open access” article. Below you can find a summary.


“Equine Gastric Ulcer Syndrome” (EGUS) is the general term used for all erosive and ulcerative diseases of the horse stomach. Based upon the affected regions in the stomach, two categories can be distinguished: “Equine Squamous Gastric Disease” (ESGD) and “Equine Glandular Gastric Disease” (EGGD).

ESGD is further divided into primary ESGD and secondary ESGD. Primary ESGD affects horses with normal gastric emptying, while secondary ESGD occurs in horses with delayed gastric emptying due to underlying pathology such as pyloric stenosis. EGGD is specified further based upon the anatomical location and the appearance of the lesion.


The prevalence of gastric ulcers varies with breed, use and level of training. There is also a difference in prevalence between ESGD and EGGD. ESGD has the highest prevalence in thoroughbred racehorses. The prevalence of EGGD is less well understood. Most lesions of EGGD are found in the antrum pyloricum.


Several studies show that there is a correlation between the presence of ulcers and the breed. The influence of age and gender is inconsistent which suggests that other factors, such as intensity and duration of training, are more important. Other factors, of which it has been described that they are a possible risk factor, are described below.

  • Grazing is shown to decrease the risk of gastric ulcers, but supporting evidence is contradictory.
  • Unlimited/frequent access to roughage is considered to reduce the risk on EGUS, but supporting evidence is not available. Besides, findings suggest that the impact of roughage without reduction of other risk factors might be less than expected. The occurrence of ESGD is more likely when straw is the only form of roughage provided. This suggests that also the type of roughage influences the prevalence of ESGD.
  • An increased interval (> 6 hours) between roughage meals increases the risk on ESGD, when compared to more frequent (< 6 hours) roughage supply.
  • An increased starch intake is consistently associated with an increased risk on ESGD in animals trained at different levels.
  • Intermittent water access increases the risk on EGUS.
  • Fasting is an often described risk factor for ESGD; intermittent fasting causes ESGD and increases its severity.

More large-scale research is needed to understand the epidemiology behind EGUS, especially behind EGGD.

Clinical symptoms

Stomach ulcers in adult horses are associated with a broad range of clinical symptoms: a decrease in appetite, slower eating, poor body condition score or weight loss, chronic diarrhoea, a bad coat condition, teeth grinding, behavioural changes, acute or recurring colic and bad performance. There is however no strong epidemiological evidence for the correlation between the presence of these clinical symptoms and the occurrence of gastric ulcers.

A broad range of clinical symptoms can occur in individual EGUS cases. On population level the different gradations of a decreased appetite and a poor body condition score are most common. Behavioural changes, including stereotypes, are inconsequent, but not unusual. EGUS can also contribute to bad performance, but considering the number of factors that can contribute to this, other factors should also be taken into account. Differences in clinical symptoms occurring with ESGD or EGGD are currently not known. Despite the large variety of possible symptoms, all these symptoms are badly correlated to the presence of EGUS. Diagnosing EGUS based on the presence of “typical clinical symptoms” should thus be avoided.


Gastroscopy remains the only reliable ante-mortem method to determine accurately if a horse has gastric ulcers. The entire stomach, including pylorus and proximal duodenum, should be included because lesions in one of these regions are easily missed.

There is no correlation between the presence of ESGD and EGGD. The presence of one cannot serve as an indication for the presence or absence of the other.

There are currently no reliable haematological or biochemical markers that can be helpful in diagnosing gastric ulcers.

Ulcer grading

The 0 – 4 “Equine Gastric Ulcer Council” system is recommended as a standard scoring system for ESGD.

Due to a lack of data to support the validity of the hierarchical grading system for EGGD, the use of this type of grading system is not recommended. For EGGD it is recommended to describe the lesion based on the presence or absence, anatomical location, distribution and appearance.

The biggest challenge is to determine the clinical relevance of the individual lesions found. There is little evidence that the presence and grading of the lesions correlates with the presence of clinical symptoms. The clinician should try to interpret the results of the endoscopy in relation to the complete clinical picture, history, etc.


ESGD is caused by an increased exposure of the squamous mucosa to acids. The relation between exposure of the squamous mucosa to gastric content and fasting and training has been described clearly. During gaits faster than a walk, the acid gastric content will be pushed up to the squamous mucosa by the increased intra-abdominal pressure.

The pathophysiology of EGGD, on the contrary, is poorly understood. The glandular mucosa differs fundamentally from the squamous mucosa by the fact that it is exposed to gastric acid in physiological conditions. For this reason it is thought that EGGD is caused by failure of the normal defence mechanisms that usually protects the mucosa against the acid gastric content. There is still no evidence that bacteria are the direct cause of EGGD.

NSAIDs have the potential to induce EGGD in individual animals, but on population level they do not contribute significantly to the prevalence of EGGD. The ulcerogenic capacity of some NSAIDs has been shown when dosages were administered that are 50% higher than the recommended dosages. When the recommended dosages are administered, phenylbutazone and suxibuzone however do not induce gastric ulcers.

It is most likely that a combination of different factors contributes to the development of EGGD in horses.


Treatment and prevention

The therapy of both ESGD and EGGD focuses on adequate suppression of acid production. The proton pomp inhibitor omeprazole is the first choice treatment. Omeprazole is superior to ranitidine.

The duration of acid suppression needed to heal ESGD and EGGD has not yet been described. Clinical studies suggest that a period of 12 hours during which the acid production is suppressed may be sufficient for the treatment of ESGD. GastroGard gives a consistent healing rate of 70-77% when administered at the registered dose of 4 mg/kg per os, once daily, during 28 days. A lower dosage and/or shorter period of administration can however be taken into consideration based on the evidence available.

The success rate of EGGD treatment is only 25%. The reason for this poor response is unknown. A longer duration of treatment may be indicated in the case of EGGD. Bacteria might also play a part. In the absence of evidence to support this theory and in the context of responsible antibiotic use, it is however not recommended to use antimicrobials in the routine treatment of EGGD.

Considering the role of mucosal defence mechanisms failing in the pathogenesis of EGGD, protecting the mucosa as part of the therapy seems legit. Sucralfate is best studied for this indication. The combination of omeprazole (4 mg/kg PO once daily) and sucralfate (12 mg/kg PO twice daily) improves the success rate of EGGD when compared to omeprazole only.

The pharmacological approach of the prevention of ESGD is comparable to the treatment. Omeprazole is used as prevention in a dosage of 1 mg/kg per os, once daily. The efficacy of omeprazole as prophylaxis for EGGD is unclear, but so far there is no difference in the prevention strategy of both.

Nutraceuticals are attractive because of the ease of use and their availability. Pectine-lecithine complexes have been shown to increase the total mucus concentration in gastric juice. Antacids seem to provide some symptomatic relief, but their effect is short-lived.

There is no strong evidence to support a specific nutritional advice. There is only little evidence for the role of the diet in the occurrence of EGGD and therefore the recommendations are primarily based on the well-known risk factors of ESGD. Continuous access to a good quality grass pasture is considered ideal. Unlimited or frequent (4-6 times daily) access to hay (at least 1.5 kg (DM)/100 kg bodyweight/day) can be an appropriate alternative. Straw should not be the only type of roughage, but it can be included safely in the diet with a maximum of 0.25 kg (DM)/100 kg bodyweight. Concentrates should be used as cautiously as possible. Sweet feed should be avoided. The diet should not contain more than 2 gram starch per kg bodyweight per day, or no more than 1 gram starch per kg bodyweight per meal. The interval between feeding concentrates should be at least 6 hours. Maize oil could help to decrease the risk of EGGD development. Water should always be available. When pastes with electrolytes are given orally, they should be diluted in water first, or mixed with the feed.

EMA advice on the withdrawal period of lidocaine in food producing animals

The EMA recently published a report on the withdrawal period of lidocaine for milk. In general, when veterinary medicinal products are used through the cascade, the minimal withdrawal period for milk is 7 days. Based on the EMA advice, the withdrawal period for lidocaine should be extended to 15 days.


The cascade

In the Netherlands lidocaine is only registered for use in dogs and cats. Lidocaine can only be used in food producing animals when the cascade is applicable. Lidocaine is mentioned on the list of active ingredients belonging to regulation (EU) no 37/2010. This is a prerequisite for the application of the cascade in food-producing animals. Other conditions are the need for treatment, particularly to avoid suffering in the animals, and the lack of a registered veterinary medicinal product for the species and indication concerned.

For equines, no MRL (Maximum Residue Level) is needed as long as the product is used for local or regional anaesthesia. For the other food producing species no MRL has been determined. When using a product through the cascade, the minimal withdrawal period should be at least as long as the withdrawal period mentioned in the SPC for the species concerned. When there is no withdrawal period mentioned for the species concerned, the withdrawal period must be at least 7 days for eggs and milk and 28 days for meat.

New insights

The MEB (Medicines Evaluation Board) in the Netherlands has requested the EMA in December 2012 to provide a scientific opinion on the usage of lidocaine in food producing animals. This request was made as a result of recent research studies in which it was shown that 2,6-xylidin is one of the most important metabolites of lidocaine in cattle and pigs. This metabolite is considered carcinogenic and genotoxic.

Besides the possible effects of exposure to the metabolite 2,6-xylidin, the MEB was also concerned about exposure to the active ingredient lidocaine. Humans are also capable of producing this carcinogenic and genotoxic metabolite of lidocaine.

What did the EMA think?

The CVMP (Committee for Medicinal Products for Veterinary Use) of the EMA concluded that 2,6-xylidin has indeed got a potential genotoxic effect, but that the conclusions drawn in different studies differ largely. A carcinogenic effect was however clearly shown according to the CVMP. Changes in the DNA could be a possible mode of action for this carcinogenic effect.

The CVMP recognised the potential risk of exposing people to lidocaine and therefore the possible formation of potentially carcinogenic and genotoxic metabolites. But it was also pointed out that, on the other hand, lidocaine is also registered for human use as a short-term oral or topical treatment. However, they did comment that the benefit-risk assessment done for the approval of lidocaine as human medicinal product also factors in the positive effects of treatment which do not count when consuming residues through animal products.


The MEB mentioned that when it was decided that no MRL was needed for equines, it was taken into consideration that the metabolite 2,6-xylidin is not produced in horses. The CVMP contradicts this and states that this metabolite is produced in horses, but to a lesser extent than in other animal species.

The CVMP did conclude that with the available information, there is no need to change the MRL for equines as mentioned in Regulation EU No 37/2010.


Previously, it was not known if cattle were able to produce the metabolite 2,6-xylidin. Based on this it was decided not to allow a MRL for use in cattle.

Recent research has shown that 2,6-xylidin is the most important metabolite that is formed in hepatocytes and microsomes extracted from livers of cattle and pigs when exposed to lidocaine. This was an in vitro study. The metabolite was however also found in the urine of cattle and pigs after the intravenous administration of lidocaine.

Hoogendoorn et al have recently published a study in which the pharmacokinetics of lidocaine and its metabolite 2,6-xylidin were described in 8 dairy cows. In these animals lidocaine with adrenaline was injected subcutaneously and intramuscularly as is done for a caesarean. Five times 30 ml was used. This study group showed that both lidocaine and 2,6-xylidin can be found in plasma, milk, muscles and kidneys.

The CVMP has calculated values below which, in theory, there should be no risk for public health. This had to be done because there is no MRL available. Based on the studies done by Hoogendoorn et al a termination half-life of 17.7 hours was used. When a two-compartment model with a rapid elimination phase is used, the advised withdrawal period for meat would have to be at least 11 days. When the same method is used, the minimal withdrawal period for milk should be 15 days.

Based on these studies and the calculations made by the CVMP, the EMA concluded that a withdrawal period of 28 days for meat is sufficient. It was however advised to extend the withdrawal period for milk to 15 days.


When it was determined that no MRL was required for equines, there was also no information available about the metabolism in pigs. Recent reports do not include information about the metabolism of lidocaine in pigs either. The metabolism in pigs is however similar to that of cattle. It can thus be concluded that the withdrawal period of 28 days for meat is also sufficient to ensure public health. For pigs, it was also taken into account that lidocaine is primarily used during castration, which is usually done within the first week of life, resulting in a long period between the administration of lidocaine and slaughter.


  1. Thuesen, L.R., and Friis, C. (2012) In vitro metabolism of lidocaine in pig, cattle and rat. Poster presentation EAVPT Congress 2012, The Netherlands.
  2. F. Verheijen, Medicines Evaluation Board Agency (2012) Request for a scientific opinion.
  3. European Medicines Agency (EMA), Committee for Medicinal Products for Veterinary Use (CVMP) (2015) CVMP assessment report regarding the request for an opinion under Article 30(3) or Regulation (EC) No 726/2004.
  4. European Medicines Agency (EMA), Committee for Medicinal Products for Veterinary Use (CVMP) (2015) Opinion of the Committee for Medicinal Products for Veterinary Use regarding a request pursuant to Article 30(3) of Regulation (EC) No 726/2004.
  5. European Medicines Agency (EMA), Committee for Medicinal Products for Veterinary Use (CVMP) (1999) Lidocaine Summary Report.

Clostridium assaults the intestines of poultry

In many flocks of laying hens the bacteria Clostridium perfringens causes a large amount of damage to the intestines. Other problems, like coccidiosis or worm infestations, facilitate the problems caused by clostridium.

“In one out of every four post mortems performed on chickens intestinal problems were the underlying reason for referral to the GD”, knows Noami de Bruijn, poultry vet and pathologist at the GD Animal Health Service. “And in one out of every three post mortems done, we actually did find enteritis”, she explained at the Poultry Relation Days held in Barneveld.


Acute intestinal problems are often caused by Clostridium perfringens. This bacterium is a natural inhabitant of the intestines and is always present. It is not exactly known yet why the bacterium sometimes suddenly turns pathogenic. “In practice, preventing stress is one of the most important preventative management measures that can be taken to minimize intestinal damage”, says poultry vet Pim Eshuis. “And that already starts in the rearing period”.


Go and visit the rearer to discuss deworming and minimising the transition to the laying farm, advised Eshuis. “Give the hens a lot of attention, especially at the start of each new round”.

Research done at the GD Animal Health Services shows that in chickens with intestinal problems caused by Clostridium perfringens, coccidiosis often plays a part as well.`

Source: De Nieuwe Oogst.

Responsible use of veterinary medicines

Lately there has been a broad societal interest in the use of veterinary medicines and specifically the use of antimicrobials. The use of antibiotics and the need to reduce their usage are in the news regularly. Also the induction of resistance and the occurrence of zoonosis are discussed often.

Mitigate risks

Every time micro-organisms are exposed to antibiotics there is a certain risk for the development of resistance. Prolonged exposure, especially in low doses, can result in the selection of resistant bacteria. Theses resistant bacteria can be transferred to humans and thus pose a threat to public health.

Applying the advised withdrawal period is important. Residues of veterinary medicines in meat, milk or eggs can pose a potential threat to public health. To minimize the risks the usage of veterinary medicines could pose to public health, it is essential to increase awareness of the risks among veterinarians and farmers and to encourage preventative measures to avoid diseases and infections. Personal protection is an easy way to reduce direct contact with antimicrobials and the possible risks. Dopharma therefore has dust masks and latex gloves in their assortment.

Responsibility - street sign illustration in front of blue sky with clouds.


The Dutch society for Veterinary medicine and the FIDIN (board for manufacturers and distributors of veterinary medicines) have developed the following recommendations on the responsible use of veterinary medicines:

  1. A good treatment starts with the correct diagnosis: determine which causative agent is responsible for the disease and focus your treatment on this micro-organism specifically.
  2. Use registered veterinary medicines: check the registration number, read the label and, if applicable, the leaflet. Consult your veterinarian regarding the right treatment.
  3. Use the recommended dosage.
  4. Do not change the method of administration (e.g. injection, intramammary treatment, treatment via drinking water or feed or topical application).
  5. Complete the treatment, even though the animals seem to already have recovered. This is important to prevent re-occurrence of the disease and development of resistance.
  6. Do not combine veterinary medicines unless this is advised by your veterinarian.
  7. Think about your own safety.
  8. Avoid exceedance of the maximum residue levels (MRLs) in animal (by-) products.
  9. Document the important details of the veterinary medicines used.
  10. Evaluate the treatment on a regular basis with your veterinarian. Always report adverse events.
  11. Read the storage conditions as mentioned on the package and always apply them.