The Synergy Of Chicken Anemia Virus And Gyrovirus Homsa 1

Chicken anemia virus(CAV)and gyrovirus homsa 1(GyH1)are both important immunosuppressive viruses in poultry,with a wide geographical distribution.Both viruses can be transmitted vertically through chicken embryos and horizontally through media such as feed and bedding grass.The pathogenicity of CAV and GyH1 is similar.The infected chickens are mainly characterized by aplastic anemia.The virus invades the lymphocytes of bone marrow,bursa of Fabricius and thymus immune organs,resulting in immunosuppression,which makes the chickens prone to secondary infection.It mainly occurs in farms with poor environmental hygiene and low levels.As one of the largest poultry breeding countries in the world,the prevalence of infectious diseases induced by CAV and GyH1 in chickens has seriously affected the healthy development of the poultry industry.The co-infection of immunosuppressive-related pathogens in large-scale poultry farms is becoming more and more common.According to a number of epidemiological investigations,since the first discovery of GyH1 virus in broiler chickens in China in 2018,CAV and GyH1co-infection have been found in large-scale chicken farms in more than ten provinces such as Shandong,Guangdong,Fujian and Shanxi in China.Its widespread prevalence has aroused the common concern of the veterinary department.Under such a severe epidemiological background,it is not clear that the specific harm caused by co-infection of CAV and GyH1 to the poultry industry is still unclear and needs to be studied urgently.The scientific question we put forward is whether CAV and GyH1 have a synergistic pathogenic effect in chickens and what mechanism synergistic pathogenicity.In this study,the animal model of CAV and GyH1 artificial co-infection of SPF chickens was established to simulate natural infection,and the sham infection group,CAV single infection group and GyH1 single infection group were set as controls to study the synergistic pathogenic effect and pathogenic mechanism of CAV and GyH1.By observing the clinical symptoms of chickens,the co-infected chickens showed more symptoms such as thinness,weakness,and depression than any single-infected chickens,and the mortality rates were 56.2 %and 45.4 % higher than those of CAV and GyH1 single-infected chickens,respectively.The results of ELISA showed that the virus shedding level of co-infected chickens increased,the antigen level in the blood increased,and the antibody production time lagged.Blood morphology examination showed that co-infection caused the increase of young red blood cells in peripheral blood.The results of blood routine examination showed that co-infection caused the number of red blood cells to maintain at an abnormally low level,and it had not been restored at 35 dpi.The results of anatomical lesions showed that CAV and GyH1 co-infection aggravated the damage to various organs of chickens,which was reflected in extensive bleeding and erosion of glandular stomach and gizzard,atrophy of spleen and bursa of Fabricius,red pulp in bone marrow replaced by adipose tissue,partial disappearance of thymic lobules only connective tissue,severe pathological changes of digestive organs and immune organs made most organs have poor prognosis at 35 dpi.In summary,CAV and GyH1 co-infection have a synergistic pathogenic effect,resulting in increased pathogenicity.This study preliminarily explored the synergistic pathogenic mechanism of co-infection.The results of histopathological observation showed that the depletion of T lymphocytes in the thymus and B lymphocytes in the bursa of Fabricius was higher than that of any single infection,which decreased the body ’s immune ability.The disappearance of hematopoietic progenitor cell islands in the bone marrow of the co-infected group led to the disorder of erythropoiesis,which clarified the molecular mechanism of aplastic anemia.The results of fluorescence quantitative PCR showed that GyH1 could significantly promote the replication of CAV in various tissues,and CAV could also promote the replication of GyH1 virus in several specific organs.In summary,the depletion of lymphocytes in the central immune organs and the synergistic replication of the virus are the key reasons for the synergistic pathogenicity of CAV and GyH1 co-infection.Both CAV and GyH1 viruses are important immunoinhibitory pathogens,and co-infection is widespread.Our study clarified the harmful effects and pathogenic rules of the increased pathogenicity of co-infection,and provided a warning for the poultry industry to improve the prevention awareness of co-infection.This study provides a new idea for the detection of chickens infected with CAV and GyH1 virus,which is conducive to carrying out field detection at the best time,eliminating positive chickens in order to better purify chickens,providing theoretical support for the rapid diagnosis of co-infection of CAV and GyH1,and also providing new scientific basis and theory for the prevention and control of immunosuppressive viruses in poultry.