| Toxoplasma gondii is an obligate intracellular zoonotic protozoan that can cause abortion in humans and animals,in addition,immunosuppressed individuals are susceptible to acute toxoplasmosis,leading to huge economic losses and serious public health threats.There have been some reports on toxoplasmosis in swine and cats of China.To further explore the epidemiology of toxoplasmosis and the mechanism of invading intestine,we investigated the infection of Toxoplasma gondii in swine from Henan,Shandong and Shanghai(2838),as well as domestic cats(28)from Zhengzhou pet hospital,besides,the risk factors were analyzed,the strains of Toxoplasma gondii were isolated,and the damage mechanism of the T.gondii on the small intestine of mice were explored.The hearts of domestic cats(28)in Zhengzhou,the hearts(305),diaphragm(2086)and blood samples(407)of swine in Henan,blood samples of swine in Shandong(10)and Shanghai(30)were collected,respectively.All the serum and diaphragm tissues washed liquid samples were detected by modified agglutination test(MAT)for the antibody of T.gondii.The risk factors of region,age and gender were analyzed.The results: the positive rate for the T.gondii antibody in swine and domestic cats were 10.08%(286/2838)and 7.14%(2/28),respectively.Among them,the infection rate of swine in Henan was 9.94%(278/2798),10.00%(1/10)in Shandong and 23.33%(7/30)in Shanghai.There was a significant difference in the infection of T.gondii between regions and age for swine(P <0.05),however,there was no significant difference in genders(P >0.05).Age and gender had no significant correlation in the infection of T.gondii for domestic cats(P >0.05).4(4/305)swine hearts and 2(2/28)cats hearts with the T.gondii antibody titer ≥25 by MAT,and the total of 2086 diaphragm were inoculated to mice,respectively.Additionally,the T.gondii in the digestive juice were detected by PCR and Nest-PCR.To the result,three groups mice of antibodies against T.gondii were positive(3/81)in the diaphragm inoculation group for swine,and one group mice of that was positive in the hearts inoculation group for domestic cats.Furthermore,T.gondii nuleic acid was detected from the three groups diaphragm of swine.One viable T.gondii strain Tg Cat CHn4(Toxo DB#9)was obtained from the cat heart tissue,but no strain was isolated from the swine.After infection of BALB/c mice with the cysts of Tg Cat CHn4,it could survive more than 60 DPI,while it could cause acute infection and death in IFN-γ-/-mouse at 16 DPI.Moreover,many tachyzoites can be observed in the lung and mesenteric lymph nodes.The results indicated that the virulence of Tg Cat CHn4 strain is attenuated,and the IFN-γ-/-mouse has a limit survival time after infection with T.gondii.104 T.gondii oocysts of Tg Cat CHn4(Toxo DB#9)and VEG strain were inoculated to BALB/c mice orally,respectively,and the VEG strain was employed as control.After inoculation,the small intestines of mice were taken and fixed at 6 HPI,1 DPI,3 DPI and 8 DPI,respectively.To explore the pathological lesions,the distribution of T.gondii antigens and the expression of lysozyme in Paneth cells,the small intestines sections were stained for H&E and immunohistochemistry(IHC)analysis.As a result,the severe lesions were observed in the ileum of VEG strain at 8 DPI.However,compared with the VEG strain,Tg Cat CHn4 had less damage in the small intestines of the mice.For the two strains,the number of PCs and granules in ileum decreased(6 HPI),then increased(3 DPI),and finally decreased at 8 DPI,the difference was not significant,compared to that in the control(P >0.05).After infection in mice with Tg Cat CHn4 strain,the expression of lysozyme in the small intestine was deficient,while it was positive at 6 HPI and 1 DPI,and then gradually decreased for VEG strain.It showed that the avirulent T.gondii may inhibit the expression of lysozyme in Paneth cells,and the deficiency of lysozyme was possibly related to the success of T.gondii in invading the intestinal of mice. |
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