Abstract:

In 2023, some goslings at a Longde Goose Farm in Kunming showed symptoms of soft neck accompanied by sporadic deaths, with the pathology suspected to be hydropericardium syndrome(HPS).The purpose of this study was to carry out molecular virological diagnosis and pathogenicity research on the etiology of gosling. Liver samples from diseased goslings were collected and inoculated with leghorn male hepatocellular cells(LMH). 1) The cytopathic effect (CPE) was observed. The culture medium was negative stained and the morphology of virus particles was observed by electron microscope. 2) The hexon gene encoding the capsid protein of the target serotype 4 fowl adenovirus (FAdV-4) was subjected to PCR diagnosis, followed by genetic evolutionary analysis of the amplified gene sequence. 3) At a dose of 5×10^5.5 TCID₅₀ per bird, subcutaneous injection was administered to healthy 10-day-old Taizhou geese for animal retroinfection to confirm its pathogenicity. The results showed that, after the inoculation of LMH cells with the supernant of disease material for 48 to 72 hours, clear cytopathic effects are observed, characterized by cell rounding, increased intercellular spaces, subsequent fragmentation, gradual detachment. Under electron microscopy, non-enveloped icosahedral viral particles were observed. The PCR test result showed positivity for FAdV-4, the virus was isolated and purified, and named strain YNKM2023;Genetic evolution analysis of the hexon gene revealed a high similarity (99.8%~99.9%) with domestically prevalent chicken and duck FAdV-4 strains, and a similarity of 99.5%~99.6% with strains isolated from India. After being infected, Taizhou geese did not exhibit severe characteristic clinical symptoms, but began to show characteristic lesions of HPS three days post-infection, with neutralizing antibodies detected six days post-infection. In conclusion, this study successfully isolated the goose-origin FAdV-4/YNKM2023 strain, which is highly homologous to the existing chicken and duck epidemic strains in the country, with no apparent genetic drift occurring. The isolated strain can infect geese, replicate in goslings causing tissue organ lesions, and trigger an immune response, showing a certain pathogenicity to geese. This contributes to understanding the prevalence of FAdV-4 in goose populations and its pathogenicity to goslings.

Key words: goose derived, fowl adenovirus type 4 (FAdV-4), isolation, pathogenicity