Postmortem Histopathological Profiling of Emerging Viral Hepatitis Syndromes in Backyard Poultry

Abstract

This study presents a comprehensive postmortem histopathological and molecular investigation of emerging viral hepatitis syndromes in backyard poultry, aiming to elucidate the etiology, lesion patterns, and viral associations in low-biosecurity smallholder systems.A complete necropsy, histological examination, and PCR-based detection of viruses were carried out on 60 birds (40 chickens and 20 ducks) with clinical signs of liver failure.  According to gross pathological observations, the high frequency of pale liver (83.3%), hepatomegaly (66.7%), and necrotic foci (63.3%) were determined, with gross changes being more expressed in chickens than in ducks.  Histopathological profiling showed that there was massive hepatic necrosis, lymphocytic infiltration, bile duct proliferation, fibrosis and formation of inclusion bodies with the highest severity rating belonging to necrosis and inclusion bodies.  PCR tests detected the avian influenza virus (H 5 N 1 ) in 36.7 percent of cases, the fowl adenovirus in 30 percent of cases and the Newcastle disease virus in 20 percent of cases. In some instances, they had infections that were identical in both groups.  Lesion severity index was highly associated with the virus type, birds infected with H 5 N 1 showed maximum lesion severity index ( 2.8 ), and adenoviruses infections were significantly associated with the development of inclusion bodies.  Anatomical mapping of lesions revealed that lesions were more in the right and cranial lobes of the liver than in the other lobes.  The gross lesions were considerably confirmed histologically and over 90 percent of pale livers were microscopically confirmed.  It was easier to diagnose using special stains such as Masson Trichrome and PAS which helped fibrotic bands and viral inclusions to stand out.  The findings of the study demonstrate the diagnostic usefulness of histopathology and special stains in differentiation of etiologies of viral hepatitis, particularly where resources are limited in backyard poultry.  The research highlights the urgent need of enhanced surveillance, molecular diagnosis and biosecurity to handle the emerging viral hepatitis concerns in small-scale poultry systems and to minimize the associated zoonotic risks.