Pathogenesis of low pathogenic avian influenza virus subtype H6N1 infection in chickens
Epidemiology Research Department
A study on the pathogenesis of a H6N1 low pathogenic avian influenza (LPAI) virus was carried out in specific-pathogen-free chickens by investigating the gross and microscopic lesions, viral antigen and RNA distribution in tissues, and viral shedding. Birds at the age of 28 days were inoculated with the LPAI virus of subtype H6N1 (A/chicken/Taiwan/19120018/2019) and sampled on 3, 7, 10, 14 days post-inoculation (dpi). The presence of viral antigen in tissues and viral RNA loads were detected by immunohistochemistry (IHC) and quantitative real time RT-PCR (qRT-PCR), respectively. No clinical signs were observed during the period of this study. Gross lesions were only found in a dead chicken on 8 dpi, which presented the lesions of renomegaly with systemic gout. Microscopically, renal tubular necrosis was observed in all infected chickens. By the IHC, the viral nucleoprotein (NP) antigen was abundantly presented in the kidneys of all infected groups. NP antigen was also found in rare epithelial cells of the bronchi on 3 dpi. The higher viral RNA in the kidney was detected by qRT-PCR on 3 and 7 dpi, in the larynx and rectum on 3 dpi, and in the bursa of Fabricius on 3 and 10 dpi. Oropharyngeal and cloacal viral shedding had been detected since 1 dpi, with higher oropharyngeal vial shedding detected on 1 to 7 dpi and cloacal on 3 dpi. All viral shedding were not detected on 14 dpi. The present study demonstrates that the main replication site of LPAI virus subtype H6N1 in chickens was the renal tubules.
Overview of development of goose hemorrhagic polyomavirus vaccine
Goose hemorrhagic nephritis is caused by the goose hemorrhagic polyomavirus. The disease mainly occurs in the 4-to-10-week-old geese. The mortality rate is 4% -67% and gooselings have higher mortality rate. Infected geese have ataxia, head, neck tremor and other neurological symptoms and excretion of blood stool. Goose hemorrhagic nephritis is one of the major diseases of the European goose, although it is not reported by the World Organization for Animal Health, it is listed as an animal quarantine disease in Taiwan. The disease is not easy to distinguish from waterfowl parvovirus infection. One of the reasons making this disease difficult to control is that the recovered diseased geese keep shedding the virus. There are no commercial vaccines available and the vaccines can only be used for feeding and management control. Vaccine development is carried out by proliferating goose hemorrhagic polyomaviruses using cell culture. The safety and efficacy tests of the vaccine were done. For goslings, the antibody titer after immunization can reach SN 1:200, tested by virus neutralization test.