Research Note: Development of an ELISA to distinguish between goose parvovirus infection and vaccine immunization antibodies

Isolation and pathogenicity of a fowl adenovirus 8b (FAdV-8b) strain in Cherry Valley ducks

AbstractInclusion body hepatitis (IBH) is an economically important viral disease primarily affecting the poultry industry. In this study, we isolated a strain of FAdV-8b (strain SDYT) from naturally infected ducks and the hexon and fiber gene sequences were analysed by polymerase chain reaction (PCR) amplification. In order to study the pathogenicity of FAdV-8b on Cherry Valley ducks, we inoculated 10- and 20-day-old ducks with 0.3 ml of FAdV-4 virus (TCID50 of 105.5/0.1 ml) either orally or intramuscularly. Clinical signs, gross lesions and histopathological changes, cytokines, viral load and antibody levels were noticed and recorded within 15 days after infection.Pathomorphological investigations revealed that ducks in the experimental group exhibited hepatitis symptoms. Histopathology showed multiple-organ damage, including serious liver and kidney lesions. Furthermore, elevated levels of inflammatory cytokines and antibodies was noticed, due to the infection and innate immune response. At later stage of infection immunosuppression occurred, resulting in decreased levels of cytokines. Determination of viral load indicated that the virus was present in several organs, with the highest viral DNA load found in the liver, followed by the kidney. Compared to birds infected orally, the intramuscular group exhibited the highest viral load. In summary, this study increases our understanding of the pathogenicity of FAdV-8b in ducks and establishes a model that will inform antiviral drug testing and vaccine evaluation for IBH, thereby preventing and reducing the spread of IBH in the poultry industry.

Rapid and visual detection of an isolated and identified goose parvovirus (GPV) strain by a loop-mediated isothermal amplification assay

Gosling plague caused by goose parvovirus (GPV), a highly infectious septic disease with high mortality, has caused substantial loss in the waterfowl industry. A method for the rapid detection of GPV is needed. In this study, we isolated the virus strain of GPV in May 2020 and applied it to the loop-mediated isothermal amplification (LAMP) assay. We designed five sets of primers for the goose parvovirus VP3 gene by LAMP. The GV-1 primer set was selected to detect GPV sensitively and rapidly. LAMP was more sensitive compared to PCR. In addition, the LAMP method could complete detection within 60 min which was faster than the PCR assay. The LAMP provided a convenient and effective experimental method for detection of GPV for inspection and quarantine departments and health care units in China, and it is expected to become a simple and routine detection method, especially suitable for goose farms.

Evidence of vertical transmission of novel duck orthoreovirus in ducks

Since 2017, duck spleen necrosis caused by new variant duck orthoreovirus (N-DRV) infection had been observed in several provinces in China. This disease retards the growth and development of ducks, thereby reducing feed return rate. N-DRV infection causes damage to duck spleen and other immune organs, leading to immunosuppression and susceptibility to other pathogens. In this study, we successfully constructed a breeding duck artificial infection model and found that N-DRV infection can cause pathologic changes, such as ovarian hemorrhage, follicle atrophy, and fallopian tube bleeding in breeding ducks, resulting in significantly reduced fertilization rate and egg hatching rate. Viral RNA was present in egg vitelline membrane, duck embryo, and duckling's spleen samples, as determined through quantitative polymerase chain reaction (qPCR). Autopsy revealed obvious pathologic changes in the spleen and other organs, although there were no obvious early clinical symptoms observed in ducklings. Sequence distance and phylogenetic analysis confirmed that N-DRV-SD19 re-isolated from the spleen samples of ducklings was consistent with the strain N-DRV-XT18 used for infecting breeding ducks. The findings in this study confirmed that N-DRV can be vertically transmitted through eggs, which provide an important reference for the disease prevention and control.