Investigation On The Epidemiology Of Toxoplasma Gondii In Primates And Basic Biological Characteristics Of TgMonkeyCHn1

Toxoplasma gondii is a ubiquitous protozoan parasite that infects many species of warm-blooded animals,including humans and non-human primates.Around a third of people worldwide are infected with T.gondii,an important zoonotic parasite.Members of the felid family,which are the definitive hosts of T.gondii and other warm-blooded animals may be intermediate hosts.This study will investigate T.gondii infection in primate samples collected in the laboratory between 2016 and2019.To understand the situation of T.gondii infection in primate populations in some areas of China,and to provide reference for the prevention and control of T.gondii infection in primates.In addition,the biological characteristics of T.gondii isolates from infected non-human primates provided basic data for studying the evolution and spread of T.gondii isolates in China.A total of 3275 human serum samples were collected from hospitals in five provinces in China.The total positive rate of T.gondii IgG antibody was 5.13%（168/3275）（95% CI,4.42-5.94） by modified agglutination antibody test（MAT）（cut-off: 1:20）.It was found that geographic location（OR=1.763）,age（OR=3.072）and female infertility（OR=2.4409）were significantly correlated with human T.gondii infection（P<0.05）.Tissues and organs from a total of 15 non-human primates were collected from zoos in Henan province between 2016 and 2019.Heart blood was tested by MAT（cut-off: 1:8）and 46.7%（7/15） of serum samples showed conversion of T.gondii Ig G antibody.A viable strain of T.gondii was successfully isolated from the myocardium of rhesus monkey by Swiss mice and IFN-γ^-/- mice,and named TgMonkeyCHn1.The strain was genotyped and virulence identified by PCR-RFLP.The results showed that TgMonkeyCHn1 genotype was a mixture of I,II and III,and the virulence protein ROP18/ROP5 genotype was 3/6,which did not match any known genotype.In addition,the seroprevalence of Swiss mice was 100% when they were intraperitoneally inoculated with ≥10³ tachyzoites of TgMonkeyCHn1.No mice died60 days after infection,and no tissue cysts were found in the brain,indicating that the strain of TgMonkeyCHn1 was non-lethal to mice.In this study,we found that the infection rate of T.gondii in Chinese residents was lower than that in the world,but there was a risk of infection.Therefore,to reduce infection,residents need to be aware of best practices for preventing toxoplasmosis,including eating well-cooked meat,drinking boiled water,washing vegetables and fruits,and handling cats cautiously.In addition,to the best of our knowledge,this is the first strain of T.gondii isolated from an Old World monkey in non-human primate research,adding to the genetic diversity of T.gondii.This study demonstrates that rhesus monkeys are the new intermediate hosts of T.gondii.