Integrating Serological and Molecular Data to Characterize Fowl Adenovirus Associated With Inclusion Body Hepatitis in Broiler Chickens From Malaysia.

BACKGROUND

Inclusion body hepatitis (IBH), caused by fowl adenoviruses (FAdVs), is an emerging disease of commercial broilers associated with significant economic losses. In Malaysia, molecular epidemiological data on circulating FAdV serotypes have largely been restricted to Peninsular regions, with limited information available from East Malaysia (Sabah), despite its rapidly expanding poultry industry and distinct production systems. This regional knowledge gap limits comprehensive understanding of FAdV transmission dynamics at the national level.

OBJECTIVES

This study aimed to detect FAdV infection in broiler flocks with IBH-compatible lesions in Sabah, Malaysia, and to characterize circulating serotypes and their phylogenetic relationships.

METHODS

Thirty pooled tissue samples (liver and gizzard) and 60 serum samples were collected from three broiler farms (YAN, KON, and NIS). FAdV detection was performed using polymerase chain reaction (PCR) targeting the hexon gene. Serological responses were assessed using enzyme-linked immunosorbent assay (ELISA). Positive PCR products were sequenced, and phylogenetic analysis was conducted to determine serotype distribution and genetic relatedness.

RESULTS

FAdV DNA was detected in 33.3% (10/30; 95% CI: 17.3-52.8) of pooled tissue samples, with detection rates of 70% (95% CI: 44.4-97.5), 20% (95% CI: 2.5-55.6) and 10% (95% CI: 0.3-44.5) in the YAN, KON and NIS farms, respectively. Although descriptive differences were observed among farms, these variations were not statistically significant (p > 0.05). All positive samples yielded the expected 897 bp hexon gene amplicon. ELISA revealed high seropositivity in unvaccinated flocks, with the highest mean antibody titre observed in the YAN farm (24,716.5 ± 4516.1). Molecular characterization identified FAdV-8b (species E) and FAdV-11 (species D), indicating co-circulation. Phylogenetic analysis showed close relatedness to strains from Korea, Belgium, China and Australia.

CONCLUSIONS

The co-circulation of FAdV-8b and FAdV-11 in Sabah broiler farms underscores the need for continuous molecular surveillance, enhanced biosecurity and breeder-level vaccination strategies using locally circulating FAdV strains to control IBH in Malaysia.