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Common occurrence of Gallid herpesvirus‐2 with reticuloendotheliosis virus in chickens caused by possible contamination of vaccine stocks

Woźniakowski, G., Mamczur, A., Samorek‐Salamonowicz, E.
Journal of applied microbiology 2015 v.118 no.4 pp. 803-808
chickens, liver, flocks, vaccines, polymerase chain reaction, spleen, Gallid alphaherpesvirus 2, loop-mediated isothermal amplification, Marek disease, Reticuloendotheliosis virus
AIMS: The aim of this study was to investigate the common occurrence of reticuloendotheliosis virus (REV) among Gallid herpesvirus 2 (GaHV‐2) infected chickens. The possible cause of this co‐occurrence may be linked to contaminated vaccine stocks, which were also examined. METHODS AND RESULTS: The study was conducted on 25 field isolates of GaHV‐2 collected between 2007 and 2013 from vaccinated chickens. Additionally, 10 commercial Marek's Disease vaccine stocks manufactured between 1993 and 2013, comprising of FC126 HVT, CVI988/Rispens and bivalent HVT + Rispens vaccines were examined. Chicken isolates were collected from the liver. Due to difficulties in differentiation between GaHV‐2 and REV, by observation of clinical signs or lesions presented in liver or spleen, loop‐mediated isothermal amplification (LAMP and RT‐LAMP) as well as PCR‐based methods were applied. CONCLUSIONS: The co‐occurrence of GaHV‐2 and REV genetic material was shown in 24 (96%) of 25 examined isolates. A marginal REV contamination was detected in three out 10 (30%) commercial vaccine stocks, mainly in bivalent HVT + Rispens vaccines produced between 2009 and 2012. SIGNIFICANCE AND IMPACT OF THE STUDY: Our results indicated the common occurrence of GaHV‐2 and REV in Polish chicken flocks, which is probably linked to contaminated HVT + Rispens vaccine stocks. Reasons for the detection of a marginal REV contamination need to be further elucidated.