Seroepidemiological Survey And Genetic Characterization Of Toxoplasma Gondii Infection In Minks And Racoon Dogs

Toxoplasma gondii is an intracellular parasite,and is widely distributed all over the world,which can infect virtually all warm-blooded animals,including humans.Cats and other felids as definitive hosts for T.gondii can excrete infectious T.gondii oocysts,meanwhile,other warm-blooded vertebrate animals serve as intermediate hosts and could be infected with T.gondii by ingesting contaminated water and food with T.gondii oocysts passed in the feces of cats or by ingesting raw or rare-cooked tissues of other intermediate hosts which contain tissue cysts.Generally,T.gondii infection rarely causes clinical symptoms in healthy individuals,however,it can cause severe diseases,even fatal to AIDS patients or those individuals with undergoing immuno-suppressive therapy.Moreover,infection with T.gondii during pregnancy may cause severe damages to the fetus by transplacental transmission,causing fetal dysplasia,abortion and stillbirth.Dreadfully,one-third of the world populations and 7.9% of Chinese people were infected with T.gondii.T.gondii can infect a large proportion of livestock and poultry in animal husbandry,causing serious economic losses.In the first part of the study,a total of 1499 mink blood samples were randomly collected from eight cities in northeastern and eastern China,and antibodies to T.gondii was examined by using the modified agglutination test(MAT).Overall,the seroprevalence of T.gondii infection was 8.14% in the examined minks.The T.gondii seroprevalence was different among cities(ranging from 1.85% in Changchun to 15.75% in Dalian),genders(male: 4.31% and female: 6.22%),seasons(spring: 11.64%;summer: 7.34%;autumn: 7.37% and winter: 7.32)and ages(young: 5.79%;subadult: 5.03%;adult: 11.08%).Region and age were considered as risk factors for T.gondii infection among the 4 factor by logistic regression analysis.The present results provided baseline data for the prevention and control of T.gondii infection in minks in China.In the second part,a total of 1181 raccoon dog blood samples were collected from Jilin and Shandong provinces,China,and the antibodies to T.gondii was examined using MAT.Overall,the seroprevalence of T.gondii infection was 8.64% in the examined raccoon dogs.The prevalences of T.gondii infection were different among cities(ranging from 2.96% in Yantai to 17.62% in Qingdao),genders(female: 7.58%;male: 9.22%)and ages(young: 8.53%;subadult: 7.71%;adult: 7.73%).Region was considered as an important risk factor for T.gondii infection by logistic regression analysis in this study.This is the first report of T.gondii infection in raccoon dogs in China,providing important reference for the prevention and control of T.gondii infection in raccoon dogs in Jilin and Shandong provinces,China.In the third part,a total of 418 minks brain tissue samples were collected from Jilin and Hebei provinces,northern China.Genomic DNA was extracted and assayed for T.gondii infection by semi-nested PCR of B1 gene.The positive DNA samples were typed at 10 genetic markers(SAG1,SAG2(5’+3’ SAG2,alter.SAG2),SAG3,BTUB,GRA6,c22-8,c29-2,L358,PK1,and Apico)using polymerase chain reaction-restriction fragment length polymorphism(PCR-RFLP)technology.36(8.6%)of 418 DNA samples were overall positive for T.gondii.Among them,5 samples were genotyped at all loci,and 1 sample was genotyped for 9 loci.In total,five samples belong to ToxoDB PCR-RFLP genotype#9,one belong to ToxoDB genotye#3.To our knowledge,this is the first report of genetic characterization of T.gondii in minks in China.Meanwhile,these results revealed the distribution of T.gondii infection in minks in China.In the fourth part,a total of 314 brain tissue samples of raccoon dogs were collected from Shandong province.Genomic DNA were extracted and assayed for T.gondii infection using semi-nested PCR targeted by B1 gene.The positive DNA samples were typed at 10 genetic markers(SAG1,SAG2(5’+3’ SAG2,alter.SAG2),SAG3,BTUB,GRA6,c22-8,c29-2,L358,PK1,and Apico)by polymerase chain reaction-restriction fragment length polymorphism(PCR-RFLP)technology to confirm genetic characterization.35(11.15%)of 314 DNA samples were detected to be positive.Only six samples were completely typed at all genetic loci,all of them represented ToxoDB genotype#9.Two samples were typed at 9 genetic loci and one was typed at 8 genetic loci,all of them represented Type I.To our knowledge,this is the first report of genetic characterization of T.gondii infection in raccoon dogs in China.These data provided base-line information for the prevention and control of T.gondii infection in raccoon dogs.