Isolation and molecular characterization of fowl adenovirus from inclusion body hepatitis cases in Western India during 2019-2021.

ABSTRACT

Background: Inclusion body hepatitis (IBH) resulted in a substantial economic loss in Western India during 2019 to 2021. Aims: The study aimed to characterize fowl adenovirus (FAdV) from field outbreaks. Methods: The study was conducted on 290 liver samples from 66 poultry flocks. The samples were subjected to histopathology and molecular detection, followed by phylogenetic typing of the partial hexon gene of the virus. Results: Spiking mortality (14%) was recorded from day 21 to day 35 with peak mortality at the 28th day of age. The necropsy showed a pale and enlarged liver with hemorrhagic and yellowish necrotic foci, accumulation of straw-colored transudate in the pericardial sac which resulted in a flabby appearance of the heart, heart enlargement, and hemorrhages on the spleen, enlarged and congested kidneys. The virus inoculation resulted in stunting and poor feathering with hepatomegaly, hemorrhages and yellowish necrotic foci on the liver as well as greenish discoloration, and kidney swelling in SPF embryonated chicken eggs. Out of 29, 16 liver samples yielded 1219 bp amplicons specific to hexon gene fragments. The sequence and phylogenetic analysis identified 14 isolates as FAdV species E serotype 11 and two as species D serotype 8b. Conclusion: The results indicated that FAdV-8b and FAdV-11 strains are involved in disease outbreaks in western India.