PATHOLOGICAL INVESTIGATION AND MOLECULAR IDENTIFICATION OF INFECTIOUS BURSAL DISEASE IN BROILER CHICKENS

Abstract

Infectious Bursal Disease (IBD) represents a highly contagious viral illness affecting young chickens, leading to immunosuppression, increased mortality rates, and stunted growth. The widespread impact of this disease has significantly undermined the poultry industry. This cross-sectional study aimed to explore the gross and histopathological alterations within various organs in suspected cases of IBD, subsequently confirmed through reverse transcription (RT-PCR) for molecular validation. This study was conducted at the Pathology Laboratory of Chattogram Veterinary and Animal Sciences University from December 2021 to February 2023. Out of 200 suspected cases of IBD identified based on gross lesions, 30 cases (comprising bursa, kidney, and spleen samples from each case) were randomly selected for histopathological investigation, while 8 samples among them were chosen specifically for molecular diagnosis. The clinical signs observed in IBD infected chickens were whitish diarrhea mixed with blood, ruffled feather, and massive death within short period. Necropsy findings revealed petechial hemorrhage in the bursa of fabricius, kidneys, thymus, spleen, and thigh muscle. Over the disease course, the bursa of fabricius displayed edematous changes in its serosal and mucosal regions, transitioning to a whitish creamy appearance and subsequent atrophy. The kidneys exhibited paleness, edema, and hemorrhagic manifestations. Depletion of follicular lymphocytes as well as edema, formation of cortical rim, interfollicular hemorrhage were the major histopathological changes found in bursa of fabricius and spleen. Kidney sections revealed hemorrhage, congestion, infiltration of inflammatory cells between renal tubules, edema in renal tubules, partially detached lining epithelium from basement membrane of many tubules. Out of thirty clinically diagnosed samples, eight samples were selected and all detected positive by RT-PCR for the hyper variable region of VP2 gene. The consistent correlation among these diagnostic modalities strengthens the confidence in utilizing gross lesion assessments, supported by histopathological and molecular analyses, as effective and reliable means for identifying Infectious Bursal Disease Virus (IBDV) infected chicken.