Isolation and identification of pigeon adenovirus 1 and analysis of its pathogenicity in pigeons and chickens.

Pigeon adenovirus type 1 predominantly infects pigeons under 12 months of age (mainly 3-5 months old), causing major clinical symptoms such as vomiting, dehydration, and discharge of thin yellow feces. In February 2023, an outbreak of a pathogen with symptoms similar to pigeon adenovirus infections occurred on a pigeon farm in Shandong Province, which was eventually identified as pigeon adenovirus type 1. In this study, a strain of PiAdV-1 was isolated from naturally infected pigeons and named pigeon-adenovirus-1-isolate-CH-SD-2023, and the hexon gene sequence as amplified and analyzed using polymerase chain reaction (PCR). To assess its pathogenicity, PiAdV-1 viral fluids were injected intramuscularly into 4-month-old pigeons and 10-day-old chickens with specific pathogen free (SPF), respectively. The results showed that the pigeons in the experimental group exhibited watery feces, whereas the chickens showed typical symptoms of thin yellow feces. Histopathologic sections showed multiple organ damage, including severe liver and intestinal damage. Liver viral load peaked on the seventh day post-infection and then declined. Viral shedding was detectable in the cloaca from the third day of infection, peaked on the seventh day, and remained detectable until 15 days post-infection. Inflammatory cytokine levels were elevated, which may have been due to infection and innate immune response. In addition, the changes in inflammatory cytokines and the damage to the bone marrow suggested that the strain may have caused severe damage to their immune system. In conclusion, these findings add to our understanding of the pathogenicity of PiAdV-1 in pigeons and chickens. The developed model will be valuable for antiviral drug testing and vaccine evaluation to prevent and reduce the spread of PiAdV-1 in the poultry industry.