[Pathologic changes in the organs in chickens after infection with the turkey herpesvirus THV-BIO-I]

The objective of our work was to investigate the dynamics of pathological lesions of chicken organs after infection with high doses of turkey herpesvirus THV-BIO-I. This virus strain is commonly used in form of the Marvak vaccine against Marek's disease of poultry in Czechoslovakia. High doses of the vaccine are used in practice with respect to the epizootological situation. The incidence of pathological lesions in the organs of Brown Leghorn chickens was investigated in a five-week experiment. One-day chickens were infected intramuscularly with the HVT strain at the doses of approximately 10(2), 10(3) and 10(4) PFU in 0.2 ml of infective inoculum per chick. The body weights of ten chickens of each group were recorded at intervals of 1, 2, 3 and 5 weeks after infection, serological examination was performed for precipitating antibodies to MDV and the feather was examined for MDV-antigen. Bursae Fabricii and spleens were weighed. Thymus, bursae Fabricii, spleens, peripheral nerves (n. ischiadicus and pl. brachialis) and gonads were sampled for histopathological examination. Neither maternal nor post-infection antibodies were found in any chick. Cytolytic lesion severity of lymphoid organs was scored using the scale of immunosuppression degrees (0-4). Morphological criteria were published in a previous paper (Halouzka and Jurajda, 1991b). The differences observed in the weights of bursa Fabricii and spleen between the infected and control chickens were not statistically significant. The observed lymphoid infiltrations in the skin, gonads, nerves and other tissues following the HVT infection are well-known and correlate with the infection dose.(ABSTRACT TRUNCATED AT 250 WORDS)