PATHOGENICITY STUDY OF “WINTERFIELD 2512 G-61 STRAIN” OF INFECTIOUS BURSAL DISEASE VIRUS VACCINE (cevac® IBD L) IN COMMERCIAL CHICKENS

Abstract

A modified form of intermediate plus of infectious bursal disease virus vaccine (CEVAC® IBD L) prepared from the “Winterfield 2512 G-61 strain” of infectious bursal disease virus was tested for it’s pathogenicity in commercial chickens. A total of 500 unvaccinated Cobb-500 commercial chicks, raised in relative isolation from day old were used. 21 chicks were collected from experimental farm at day Du, Dis, Dis, Diz, Doo Dz and Dz, respectively. 3 chicks were collected randomly from experimental flock each respective day. Vaccine was administered at ocular route at Du and Di with drinking water. All the sampled birds were subjected to detailed necropsy. The visible gross morbid lesions, bursa-body weight ratios were recorded. The bursae were collected, preserved at 10% formalin, processed, sectioned and stained with Hematoxylin & Eosin for histopathology including determination of bursal lesions scores. Data were analyzed statistically. One typically affected flock was included in this study for the comparison. The visible gross morbid lesion was not observed during necropsy and bursa-body weight ratios were 2.75+0.60, 2.7140.39, 2.44+0.42, 3.39+0.13, 2.5840.55, and 2.15+0.16, 2.41+0.28 at Du, Dis, Dis, Diz, Dan Das, and D2, respectively. Histopathological lesions were characterized as normal to severe lymphoid depletion with varying degrees of follicular atrophy in the vaccinated flock of study work. The bursal lesions scored were 0.67+0.33, 0.67+0.33, 2.00+0.58, 0.6740.33, 1.0£0.00, and 0.6740.33, 0.3340.33 at Dn, Du, Dis, Diz, Doo Das, and Dz, respectively. No outbreaks were noted in the vaccinated flock, but significant changes were found in the affected flock.