A primary occurrence of inclusion body hepatitis in absence of predisposing agents in commercial broilers in Iran: a case report

Background: Fowl adenoviruses (FAdVs) associated with certain clinical diseases including inclusion body hepatitis (IBH) have become of considerable importance in the poultry industry. Currently, an increasing number of IBH outbreaks in different parts of Iranian poultry industries is a growing concern. Infectious bursal disease virus (IBDV) or chicken infectious anemia virus (CIAV) have historically been incriminated as predisposing factors for FAdVs to cause IBH. Furthermore, some have speculated whether IBDV vaccine strains impact on IBH clinical manifestation. The present report assesses the potential predisposing role of IBDV, CIAV, and infectious bursal disease)IBD( vaccine strains for FAdVs in the course of an IBH occurrence in the field. Case description: 90000 day-old broiler chickens with the same parent source were housed, at 4 day-interval, in two commercial farms in Shiraz, Iran. Increased mortality with lesions of hepatitis, suggestive of IBH, started in the primitive farm right after blind prescription of IBD vaccine at the age of 12-days-old. Consequently, IBD vaccination was postponed for the apparently healthy chickens of the other farm in which chickens were monitored for the occurrence of IBH afterwards. Laboratory examination was followed by histopathology and polymerase chain reaction (PCR) on liver, cloacal bursa, and thymus samples to determine the involvement of FAdV, IBDV, and CIAV in the occurrence of the disease. Findings/treatment and outcome: No evidence was found to support the predisposing role of neither IBD vaccination nor IBDV/CIAV infection in this IBH occurence. The results also demonstrated a primary role of the FAdV-11 as a causal agent of the IBH occurrence. Conclusion: The findings suggest that certain FAdVs are pathogenic enough to primarily induce IBH in young broilers.