Dubey J P, Su C, Cortés J A, Sundar N, Gomez-Marin J E, Polo L J, Zambrano L, Mora L E, Lora F, Jimenez J, Kwok O C H, Shen S K, Zhang X, Nieto A, Thulliez P
United States Department of Agriculture, Agricultural Research Service, Animal and Natural Resources Institute, Animal Parasitic Diseases Laboratory, Beltsville, MD 20705-2350, USA.
Vet Parasitol. 2006 Oct 10;141(1-2):42-7. doi: 10.1016/j.vetpar.2006.04.037. Epub 2006 Jun 22.
Cats are important in the epidemiology of Toxoplasma gondii infection because they are the only hosts that can excrete the environmentally-resistant oocysts. In the present study, prevalence of T. gondii was determined in serum, feces, and tissues of 170 unwanted cats from Colombia, South America. Antibodies to T. gondii were assayed by the modified agglutination test and found in 77 of 170 (45.2%) cats with titers of <1:5 in 93, 1:5 in eight, 1:10 in 17, 1:20 in 10, 1:40 in seven, 1:80 in four, 1:160 in eight, 1:320 in six, and 1:640 or higher in 17 cats. T. gondii oocysts were not found in feces of any cat as ascertained by bioassay in mice. Tissues (brain, heart, tongue) of 116 cats were bioassayed in mice or cats. T. gondii was isolated from tissues of 15 of the 42 cats with titers of 1:40 or higher and not from any of the 90 cats titers of 1:20 or lower. Of the 29 cats whose tissues were bioassayed individually, T. gondii was isolated from the tongues of nine, hearts of eight, and brains of five. Mice inoculated with tissues of 12 of 15 infected cats died of toxoplasmosis; with nine T. gondii isolates all infected mice died. Overall, 65 of 92 (70%) of T. gondii-infected mice died of toxoplasmosis. Genotyping of these 15 isolates using polymorphisms at the SAG1, SAG2, SAG3, BTUB, and GRA6 loci revealed that three isolates (TgCtCo1, 2, and 7) had Type I alleles and one isolate (TgCtCo8) had Type II allele at all five loci. Eleven isolates contained the combination of Type I and III alleles and were divided into three genotypes, with TgCtCo3,5,6,9,12,13 and 15 had alleles I, I, III, I and III, TgCtCo4,10,11 had alleles I, III, III, I and I, and TgCtCo14 had alleles I, III, III, III, and III, at loci SAG1, SAG2, SAG3, BTUB and GRA6, respectively. All infected mice from each group had identical genotype except one mouse infected with TgCtCo5 had a Type III allele at locus BTUB and a unique allele (u-1) at locus SAG1 indicating mixed infection for TgCtCo5, whereas the rest seven mice had a Type I alleles at both loci.
猫在刚地弓形虫感染的流行病学中很重要，因为它们是唯一能排出具有环境抵抗力的卵囊的宿主。在本研究中，测定了来自南美洲哥伦比亚的170只流浪猫的血清、粪便和组织中的刚地弓形虫感染率。通过改良凝集试验检测刚地弓形虫抗体，在170只猫中有77只（45.2%）检测到抗体，其中93只滴度<1:5，8只滴度为1:5，17只滴度为1:10，10只滴度为1:20，7只滴度为1:40，4只滴度为1:80，8只滴度为1:160，6只滴度为1:320，17只滴度为1:640或更高。通过小鼠生物测定法确定，任何一只猫的粪便中均未发现刚地弓形虫卵囊。对116只猫的组织（脑、心脏、舌头）进行了小鼠或猫的生物测定。在42只滴度为1:40或更高的猫中，有15只猫的组织分离出了刚地弓形虫，而90只滴度为1:20或更低的猫中均未分离出。在29只单独进行组织生物测定的猫中，有9只猫的舌头、8只猫的心脏和5只猫的脑部分离出了刚地弓形虫。用15只感染猫中12只猫的组织接种的小鼠死于弓形虫病；用9株刚地弓形虫分离株感染的所有小鼠均死亡。总体而言，92只感染刚地弓形虫的小鼠中有65只（70%）死于弓形虫病。利用SAG1、SAG2、SAG3、BTUB和GRA6位点的多态性对这15株分离株进行基因分型，结果显示，3株分离株（TgCtCo1、2和7）在所有5个位点均具有I型等位基因，1株分离株（TgCtCo8）在所有5个位点均具有II型等位基因。11株分离株包含I型和III型等位基因的组合，分为3种基因型，在SAG1、SAG2、SAG3、BTUB和GRA6位点，TgCtCo3、5、6、9、12、13和15分别具有等位基因I、I、III、I和III，TgCtCo4、10、11分别具有等位基因I、III、III、I和I；TgCtCo14分别具有等位基因I、III、III、III和III。除一只感染TgCtCo5的小鼠在BTUB位点具有III型等位基因且在SAG1位点具有独特等位基因（u-1），表明TgCtCo5为混合感染外，其余7只小鼠在两个位点均具有I型等位基因，每组所有感染小鼠的基因型均相同。
