Effects of different hydropericardium syndrome (HPS) vaccines on lymphoid organs of broilers

The present study was conducted to evaluate the efficacy of different types of vaccines against HPS, their effects on growth traits and the immune organs (bursa and thymus), and immunomodulatory effects on immunity against Newcastle disease virus and infectious bursal disease virus. Effort was also made to measure the extent of stress caused by different types of vaccines against HPS. For this purpose 250 day old broiler chicks were divided into 5 groups A, B, C, D and E. On day 12 of age the birds of group B were vaccinated with an oil based Angavac vaccine and birds of groups C, D and E were vaccinated with formalinized killed vaccines prepared from liver homogenates of affected birds by different manufacturers locally, while birds of group A were kept as unvaccinated/untreated control. Blood was collected from 10 birds of each group oil 24, 48, 72 and 96 hours post-vaccination i.e. day 13, 14, 15, and 16 of age for preparation of slides for differential leukocyte count. Serum was collected from 10 randomly selected birds of each group on clay 14, 28 and 42 of age for determination of antibody titres against NDV, IBDV and HPSV. Oil based vaccine evoked a slow steady and persistent pattern while formalinized killed vaccine provoked enhanced early level which decreased rapidly and did not persist to a level of protection uptil 42 days of age. Negative immunomodulation was observed clue to all types of HPS vaccine against antibody titre of ND. The extent of immunomodulation was mild in case of oil based and severe in case of formalinized killed HPS vaccines. But no immunomodulation observed against antibody titres of IBD. The stress was a result of all types of vaccines. The oil based vaccine produced transient type of stress as compared to severe and prolonged stress produced by the formalinized killed HPS vaccines. It can be concluded that the oil based Angavac vaccine against hydropericardium syndrome exerts lo w level of stress and with persistent high antibody titres improves health status of flock.