Abstract:
A total of 2320 blood samples and 409 egg samples were analyzed for the presence of antibodies to various strains of avian infectious bronchitis virus (AIBA). For this purpose, commercial broiler, broiler breeder, commercial layer, and layer breeder farms located in various geographical regions of the provinces of Punjab and northwestern frontier province (NWFP) were visited, and flock histories in terms of performances, growth patterns and IB disease prevalence, vaccines and vaccination programs and mortality were recorded. Samples of blood from locally bred desi birds and pheasants were also collected. Attempts were made to sample only those farms which had experienced high morbidity, low production and mortality in past growing or laying flocks housed at such farms. Samples from acute phase of illness and convalescent period were collected where-ever possible. It was observed that there was a general trend to house and rear multiple age groups at the same time, the poultry farms were located at a very close distance from each other and were either not following any proper vaccination programs or were not using any IBV vaccines. The seroprevalence of IBV antibodies in unvaccinated flocks was more in areas where poultry farms were located in clusters or had developed into poultry estates. In case of commercial layers, layer breeder and broiler breeder birds their misshapen and normal eggs were also collected for detection of antibodies to various strains/types of IBV. The serum and egg-yolk were analyzed using the haemagglutination-inhibition and agar gel precipitation tests.
This study indicated the presence of antibodies to various AIBV types such as Arkansas, Massachusettes-41 (M-41), JNK, D-27A and D-1466. It was further observed that the breeder and commercial flocks which did not receive and killed or live IBV vaccination had significant levels of humoral and yolk antibodies indicating that various types of IBV were circulating in the poultry flocks in various areas of Punjab and NWFP. The flocks indicating low egg production and quality and respiratory distress and poor feed conversion rations did suffer from the attack of some IBV strain(s) as they also had quite significant level humoral/yolk IBV antibodies.
