Abstract:By using three different routes of infection with Fukaya strain of Toxoplasma gondii, the characteristics of chronic lesions and the formation of cysts in the brain of the infected mice were observed in order to set up a chronic animal model for the studies on the pathogenesis and diagnosis of toxoplasmosis. Mice were infected with tachyzoites of Fukaya strain (5 x10~4) by intraperitoneal inoculation (IP), subcutaneous injection (SC) and per-oral gavage (PO), and the chronic infection was established after treatment with certain amount of drugs with the control group of mice without giving any drugs. The brain samples of the infected mice were taken at 3, 6, 14, 21, 28, 42 and 90 days after infection and the parasites were detected by indirect immunoenzymatic staining. The count of parasites in the brain was determined and the cyst formation in each case was observed. It was demonstrated that the count of parasites in the peritoneal cavity of the IP-infected mice was found to be the highest one among these 3 groups of mice at 3 and 6 days after infection,and showing a tendency of IP>SC>PO.The count of parasites in the brain of IP-infected mice reached its peak value at 28 th day after infection, so did as the cyst count in the brain, and those of the SC-infected mice showed its peak in the brain at 21?th day after infection, also for the cyst count in the brain. In PO-infected mice, parasite count peaked also at 21?th day after infection, but cysts in the brain were seldom found, suggesting that cysts could not be easily formed by route of per-oral lavage. The (iviabilities) of mice at 42 days after infection by these 3 routes were 100%, 66% and 80% respectively. It is concluded that brains of mice are usually infected during chronic stage of the toxoplasma infection, in which the cysts are easily formed in case of infection infected by peritoneal and subcutaneous routes than those infected by per-oral route.
(1)Conley F K , Jenkins K A. Immunohistological study of anatomicrelationship of Toxoplasma antigens to the inflammatory response inbrains of mice chronically infected withToxoplasma gondii(J). InfImmun,1981,31:1184.
(2)Kitta S, kitta C, Henry L, et al. A histological and immunohisto-chemical study of the change sinduced in the brains of white mice byinfection withToxoplasma gondii(J).Br J Exp Path,1984,65:67.
(3)Conley F K , Jenkins K A, Remington J S, et al.Toxoplasmagondiiinfection of the central nervous system :use of peroxidase-an-tiperoxidase method to demonstrateToxoplasma gondiiin formalinfixed ,paraffic embedded tissue sections(J).Hum Pathol,1981,12:690.
(4)Arnold S J ,Kinney M C, McCormick M S,et al. Disseminated tox-oplasmosis: unusual presentations in the immunocompromised host(J.)Arch Pathol Lab Med ,1997,121:869.
(5)刘俊燕,杨秀珍,吴增强,等.弓形虫RH株在实验感染小鼠体内分布的研究(J).中国人兽共患病杂志,2000,16(4):37.
(6)张爱民,陆琴,杨惠珍,等.弓形虫脑组织包囊两种分离法的比较(J).中国人兽共患病杂,1996,12(3):39.
(7)Ferguson D J P,Hutchison W M. An ultrastructural study of theearly development and tissue cyst formation ofToxoplasma gondiiin the brains of mice(J).Parasitol Res,1987,73:483.
(8)Zenner L, Darcy F, Capron A, et al.Toxoplasma gondii:Kineticsof the dissemination in the host tissues during the acute phase of in-fection of mice and rats(J).Exp parasitol,1998,90:86.
(9)Sahm M, Grob U, Reiter-Owona I, et al. Infection and stage con-version during murine pulmonary toxoplasmosis :A study with threedifferent strains ofToxoplasma gondii(J), J Parasitol,1998,84(4):723.
(10)沈继龙,徐秉锟.隐性弓形虫感染的活化和包囊的形成(J).中国寄生虫学与寄生虫病杂志,1991,9:102.
(11)于恩庶主编.弓形虫病学(M).福州:福建科学技术出版社,1992.1-160.
(12)Dubey J P,Lindsay D S, Speer C A,et al.Structures ofToxoplas-ma gondiitachyzoite, bradyzoites, and sporozoites and biology anddevelopment of tissue cysts(J).Clin Microbiol Rev,1998,11:294.
(13)Jacobs L,Reminton J S,Melton M L, et al. The resistance of theencysted form ofToxoplasma gondii(J).J Parasitol,1960,46:11.