The purpose of the experiment was to define whether and to what extent can prophylactic vaccinations against Newcastle disease (ND) and haemorrhagic enteritis (HE) affect the humoral and cellular response in pheasants. The evaluation of humoral response was performed on a basis of agglutinin titre after administered antigen and the cellular immunity index was the delayed type hypersensitivity (DTH) reaction. The pheasants were prophylactically vaccinated against Newcastle Disease (ND) on the 1 st , 28 th and 56 th day of life. Moreover, on the 49 th day of life, part of the birds was given in the drinking water a vaccine containing the HEV (Haemorrhagic Enteritis Virus). Fourteen days after the HEV vaccination, the birds were intravenously given 0.5 ml of the 10% SRBC (sheep red blood cells) suspension. Simultaneously with the SRBC administration the delayed hypersensitivity test was performed by intradermal administration of phytohaemagglutinin (PHA). It was shown that in pheasants vaccinated with NDV and additionally with HEV, the specific agglutinin anti-SRBC titre was significantly (p < 0.05) lower than in birds vaccinated against ND only. It also appeared that, the antibodies resistant to 2-mercaptoethanol were 43% of the total pool of specific anti-SRBC antibodies in the NDV vaccinated birds, whereas in birds vaccinated also with HEV they were 75%. No significant differences were found in the DTH test. Only in the HEV vaccinated pheasants the tendency to increase the wing index value was noted. The results confirm the observations concerning immunosuppressive effects of simultaneous vaccinations. They also indicate that overloading the pheasants with many antigens (ND and HEV vaccination) may weaken the humoral response to administered SRBC.
HEV vaccination, NDV vaccination, anti-SRBC antibody titre, delayed type hypersensitivity (DTH), pheasantsThe main role of the immune system is to distinguish between what is its own and what is foreign and to eliminate any threat that may impair homeostasis. The threat is recognized much faster when the factor causing it is known. This knowledge has been used in prevention of animal infectious diseases for years, hence, the use of vaccines containing attenuated pathogenic antigens (Ahmad and Sharma 1993;Pierson and Fitzgerald 2003). The rate and quality of the response depend on animal species and individual cases. In birds, this is influenced by numerous factors, mainly genetic, resulting from natural selection or breeding conditions provided (Kunze et al. 1996;Boa-Amponsem et al. 1999; Talebi et al. 2005). Practically, the key role is attributed to environmental conditions, understood in a very broad sense. As has been shown, the transfer of wild animals into any housing system brings about the threat of increased susceptibility to bacterial and viral diseases. According to many researchers, the increased susceptibility of birds to infectious diseases is an effect of various immunosuppressors (Dohms and Metz