Molecular phylodynamics of fowl adenovirus serotype 11 and 8b from inclusion body hepatitis outbreaks.

Fowl adenovirus (FAdV) serotypes are involved in a variety of clinical manifestations in poultry and has resulted in substantial economic loss to the poultry farmers. Despite the endemicity of Inclusion body hepatitis (IBH) in South Asian countries, including India, its etiology is not well studied. In western India, the rural poultry flocks obtained from the vaccinated parents were experiencing disease outbreaks with substantial economic losses due to heavy outbreaks and mortality. Therefore, the study was conducted to decipher the molecular epidemiology of the FAdV from field outbreaks in western India. A total of 37 commercial broiler poultry flocks and 29 village poultry flocks of western India were visited during 2019 to 2021. Out of these, 19.14% flocks showed incidence of IBH during the age of 15 to 35 days. The mortality ranged from 3.3 percent to 55.28 percent. The samples were subjected for amplification of partial hexon gene covering loop 1 and loop 2. The results revealed 48.28% positivity by PCR. The sequence analysis identified 14 isolates as species D serotype 11 with 0.97 to 0.99% divergence and two as species E serotype 8b with 0.99% divergence. The FAdV-11 isolates showed amino acid substitutions D195N, T399A, N417S, and N496H. The amino acids I188 and N195 were conserved in FAdV-11. The molecular clock in Bayesian methods was used to determine most common ancestor. The isolates MH379249 and MH379248 were determined the most recent common ancestor for FAdV-11 and FAdV-8b isolates. The analysis suggested evolution of 10 FAdV-11 strains in 2012, and four FAdV-11 strains and two FAdV-8b strains in 2018.