Is vaccinating turkeys against Marek’s disease justified?

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Marcin Śmiałek DVSc1, Joanna Kowalczyk DVM1, Adam Śmiałek DVM2, Prof. Andrzej Koncicki1

“Marek’s Disease (MD) is a viral disease of foraging poultry affecting chickens, Japanese quail and presently also turkeys” was the simple lead-in to the section dealing with the issue of Marek’s Disease in poultry flocks authored by Professor Elżbieta Samorek Salamonowicz in the compendium edited by the late Professor Michał Mazurkiewicz entitled “Choroby Drobiu [Poultry Diseases]”. Despite the simplicity of that sentence, we have come to understand that many different opinions are current with regard to this particular point – “presently also turkeys”. Live naturally apathogenic (HVT) or attenuated (Rispens) vaccines are used in the specific prophylaxis of MD, given to birds on their first day of life via subcutaneous or intramuscular injections.

Reviewing the scientific literature and publications in popular science, it was difficult to find works written with a focus on purely practical matters and addressing the question of whether to vaccinate or not.. In the course of the review, we nevertheless reached the conclusion that the answer is affirmative; however, it depends upon several factors, chief among which are the particular vaccine which is intended to be administered and how real the risk is of disease in the particular turkey flock. The principal findings collated from individual data presented in a review article of July 2017 may be summarised as follows:

  1. HVT. Assuming the main source of Marek’s Disease Virus (MDV) infection in turkeys is chickens, the HVT vaccine should only be expected to protect birds against the first serotype with relatively low virulence (m/vMDV), and will be no match for the viruses which are dominant in Poland with higher virulence (vv/vv+MDV).
  2. Rispens. The application of this strain in the specific prophylaxis of MD broadens the range of protection to include higher virulence MDV. Unfortunately, this vaccine may transpire to be ineffective in the light of the emergence of oncogenic “turkey” strains of MDV in a given region. The capacity of the Rispens strain to replicate effectively in lymphatic system cells has not been elucidated to date, and neither, as a corollary, has its potential to have consequences collectively described as immunosuppressive.
  3. Rispens + HVT. The application of this vaccine gives the best effects in terms of imparting of protection against infection with high-virulence MDV (vv/vv+MDV). Its main drawback may once again turn out to be the potential to have immunosuppressive action.

This summarises an article published in Polski Drobiarstwo [Polish Poultry Farming], issue 7, 2017. The full article may be found at https://polskie-drobiarstwo.pl/archiwum/numery/177

1Chair of Avian Diseases, Department of Veterinary Medicine, University of Warmia and Mazury in Olsztyn, Poland
2Veterinary Surgery, Leszczynek 11A, 99-300 Kutno, Poland