A serological survey on the prevalence of antibodies against Salmonella and Mycoplasma gallisepticum (MG) was carried out in layer chickens in Rajshahi and surrounding districts of Bangladesh. A total of 605 sera samples were examined by rapid plate agglutination (RPA) test using commercial Salmonella and MG antigens to determine the Salmonella and MG specific antibody. Out of 605 sera samples 14.1% showed single Salmonella, 45.1% showed single MG and 11.2% showed their concurrent infection. Prevalence of Salmonella was recorded the highest (37.6%) in adult compared to young (16.7%). On the contrary, MG and concurrent infections were recorded the highest (71.7% and 13.3%) in young compared to adult (50.4% and 10.4%). The prevalence of Salmonella, MG and concurrent infections were recorded the highest (34.3%, 68.6% and 17.1%) in large flocks compared to small flocks (21.3%, 50.0% and 8.8%). The prevalence of Salmonella infection was the highest (30.4%) in summer followed by winter (23.7%), rainy (25.0%) and autumn (23.3%). The prevalence of MG infection was the highest (61.6%) in winter followed by autumn (56.9%), rainy (55.0%) and summer (49.6%). Whereas, their concurrent infection was the highest (12.1%) in winter followed by summer (11.9%), rainy (10.8%) and autumn (10.0%).

The comparative efficacy between the conventional vaccine (DLS-DPV) and experimentally prepared duck plague vaccine (BAU-DPV) was evaluated in seventy-five 35-day-old Zinding breed ducklings during the period from October/02 to March/03. The ducklings were equally divided into five groups (A, B, C, D and E). Ducklings of group A and B were primarily vaccinated with 0.5 ml and 1.0 ml of DLS-DPV respectively and those of group C and D were primarily vaccinated with 0.5 ml and 1.0 ml of BAU-DPV. The ducklings of group E were kept as unvaccinated control. Five months after primary vaccination all the ducks of vaccinated groups were boosted with 1.0 ml of DLS-DPV and BAU-DPV and 21 days after booster vaccination all the ducks of vaccinated and control groups were challenged with 1ml of 10 EID of virulent 4 50 field isolate of duck plague virus (DPV). The level of immunity developed in different vaccinated groups of ducks was measured by passive hemagglutination (PHA) test. The mean PHA titre of birds of group A, B, C and D after primary vaccination were 38.