Pathogenic Features Of Gyrovirus 3(GyV3) In Chickens And Mice

Transmissible viral proventriculitis(TVP)mainly causes symptoms such as weight loss,fecal material,and proventricular enlargement in chickens.The disease can significantly increase the feed to meat ratio,reduce the production of chicken,and bring huge economic losses to the broiler breeding industry.TVP has become the main problem in broiler breeding.But the cause of TVP has not been clear.In 2018,GyV3 was isolated from white feathere broilers with TVP for the first time in this experiment,and GyV3 was confirmed to be an important cause of TVP through retrospective epidemiological investigation and regression animal experiments.The GyV3 is a single-stranded circular DNA virus and belongs to the Gyrovirus genus of Anelloviridae.It was first isolated and identified in children's feces of acute gastroenteritis in Chile and Hong Kong in 2012.Subsequent research did not detect its source,so can GyV3 be transmitted between humans and chickens? Are there public safety issues? This issue is unknown.In order to solve this problem,we use chickens and mice as experimental animals.Through pathogenicity experiments and virus transmission experiments,we deeply study the pathogenic characteristics and transmission modes of GyV3,and provide scientific basis for GyV3 prevention and control and its public health and safety decisions.To clarify the transmission mode of GyV3 in chickens and rats,a model of horizontal and vertical transmission of GyV3 infected chickens and a model of horizontal transmission of GyV3 infected mice were established.One-day-old SPF chicks were intraperitoneally inoculated with GyV3-SDAU-1 strain as a direct infection group,PBS was inoculated intraperitoneally and the direct infection group was co-cultured as a contact infection group,and PBS was inoculated intraperitoneally and fed separately as a control group to establish a horizontal spread model of GyV3 infected chickens.GyV3-SDAU-1 strain was inoculated into 6-yolk yolk sacs of chicken embryos as a vertical direct infection group,and yolk sacs were inoculated with PBS as a control group,incubated until husks,isolated and reared,and a model of vertical transmission of GyV3 infected chickens was established;BALB/c at 4 weeks of age young mice were inoculated intraperitoneally with GyV3-SDAU-1 strain as a direct infection group,PBS was inoculated intraperitoneally and reared with the direct infection group as a contact infection group,and PBS was inoculated intraperitoneally and fed separately as a control group to establish a model of horizontal transmission of GyV3 infected mice.Through clinical observation,gross necropsy observation,hemogram observation,histopathological observation and immunohistochemical detection,the transmission mode and transmission ratio of GyV3 in chickens and rats were detected.The results showed that GyV3 can be transmitted horizontally and vertically in the flock.The horizontal transmission infection rate is 50%,the mortality rate is 12.5%,the vertical transmission infection rate is 100%,and the mortality rate is 0.The vertical infection ability of GyV3 is higher than that of exposure.Ability to infect,and both the contact infection group and the vertical direct infection group can produce the same symptoms as the direct infection group;GyV3 can be transmitted horizontally in the herd,the horizontal transmission infection rate is 50%,the mouse has no death,and can produce and direct infection In the group with the same symptoms,GyV3 had a lower pathogenic capacity to mice.In order to study the pathogenicity of GyV3 to chickens and mice and compare the differences between them,this study also established GyV3 artificially infected chicken and mouse animal models.One-day-old SPF chicks and four-week-old BALB / c young mice were intraperitoneally inoculated with GyV3-SDAU-1 strain as a direct infection group,and PBS was inoculated intraperitoneally and isolated as a control group.Clinical observation,gross necropsy observation,and hemogram Observation,histopathological observation,viral load detection and virus distribution detection were used to study its pathogenic characteristics.The clinical manifestations of GyV3-infected chickens are debilitating,sluggish,and stunted;gross necropsy shows that the organs are lighter in color,proventricular enlargement,proventricular papillary enlargement and adhesion,pale bone marrow,and bursa;The infection rate is 81.82%,and the mortality rate is 21.86%.Observation of the blood image showed a marked increase in young red blood cells and heterophilic leukocytes;histopathological observation showed diffuse lymphocytic infiltration in the proventricular mucosa layer and interglandular ducts,obstruction of the ducts of the proventricular papilla,proliferation of duodenal mucosal epithelial cells,and renal marrow Degeneration and necrosis of tubule epithelial cells,scattered inflammatory foci in the adrenal glands and testes.Viral load tests showed that 14 dpi,21dpi,and 28 dpi adrenal,testicular,and bone marrow loads were higher,while proventricular and spleen loads were lower,and tissue loads were higher at 21 dpi than 14 dpi and 28 dpi.Immunohistochemistry analysis of GyV3 distribution in the body showed that positive signals were detected in the kidney,brain,duodenum,bursa,and adrenal glands.The clinical manifestations of GyV3 infected mice were low appetite and growth retardation;gross autopsy showed that the color of each organ was light;the infection rate was 41.67%,and no death occurred.Blood image observation shows that the central refractive zone of red blood cells is enlarged.Only the edges of red blood cells are stained,and platelets are significantly increased.Histopathological observations show diffuse hepatocyte degeneration and necrosis of liver cells,local bleeding between renal tubules,testicular germ cells,and spleen.The megakaryocytes increased,inflammatory lesions were seen in the stomach,and a large number of cells proliferated between the chyloducts in the central duodenum.Viral load tests showed that 14 dpi,21dpi,and 28 dpi testis and brain loads were higher,stomach and spleen loads were lower,and tissue loads were higher at 21 dpi than 14 dpi and 28 dpi.Immunohistochemical analysis of GyV3 distribution in the body showed that positive signals were detected in the stomach,brain and testes.By comparing the pathogenic characteristics of chickens and mice infected with GyV3,it was found that the clinical manifestations of chickens and mice were similar,and both showed gastroenteritis and anemia symptoms;while the viral load and expression were different,GyV3 was found in chicken adrenal glands and kidney.The expression level of replication is higher,and it is higher in the brain and testes of mice.In summary,GyV3 can cause infectious viral adenitis and anemia in chickens,and can infect mice across species,causing gastroenteritis and anemia in mice,but GyV3 infected chickens and mice have different target organs.In addition,GyV3 can spread horizontally and vertically in flocks and horizontally in rats.This study not only clarifies the direction for subsequent research on the pathogenic mechanism of GyV3,but also provides scientific theoretical basis for GyV3 prevention and control and public health safety decision-making.