POSSIBILITIES OF PREVENTION OF DERZSYS-DI SEASE

The protective value of an experimental inactivated o w oil-emulsion v accine containing 105.2 TCID50 of cell-culture grown goose parvovirus and 105.9 EID50 of Muscovy duck egg grown Muscovy duck parvovirus per vaccine dose was compared with the protective value of an attenuated l ive virus vaccine and with that of a biosynthetic subunit vaccine. Vir us neutralization titers of vaccinated laying geese and progeny with m aternal immunity as well as the health status and weight gain of proge ny after challenge infection with virulent virus Derzsy B served as cr iteria of evaluation. Layers perimmunized with a live virus vaccine at growing age were vaccinated before the laying season as follows: 2 in jections with the experimental inactivated vaccine. 1 injection with t he biosynthetic subunit vaccine as recommanded: 2 injections of the at tenuated vaccine were given before and 1 injection in the middle of la ying season. After the 1st injection of experimental vaccine VN titer of layers reached the mean value of 1020 as the highest level then it deceased gradually to 1:300 and had barely changed up to the end of la ying season (1:253). VN titer of layers immunized with the attenuated vaccine reached the highest level on week 1 (1:818), then it decreased to 1:253 by the time of the 3rd vaccination: however it showed a slow increase and amounted to 1:520 also at the closing of experiment. The highest mean VN titer (1:1213) was shown by layers immunized with the biosynthetic subunit vaccine then it decreased during the laying peri od and reached the lowest level of 1:50 by the end of the production p eriod (Figure 1). Tendencies of VN titers in progeny were similar to t hose in laying geese as measured at the beginning, in the middle and a t the end of laying period (Figures 2 and 3) and this was proven also by the results of challenge - infection of progeny from eggs of vaccin ates (Figure 4). By the examinations authors have demonstrated that 2 injections of their inactivated vaccine given before the laying season can induce in layers preimmunized with a live virus vaccine at growin g age a VN titer which affords goslings adequate maternal protection ( at least 1:50 VN titer at hatching) up to the end of laying season.