Toxoplasma gondii is a worldwide parasite that can infect the central nervous system of warm-blooded animals, including humans. The infection is acquired mainly by eating food or water contaminated with oocyst or tissue cysts of T. gondii [1]. A zoonotic infection of this parasite leads to an asymptomatic infection in healthy persons. Clinical toxoplasmosis appears to occur by reactivation of the infection in individuals who are immunocompromised, especially patients with acquired immunodeficiency syndrome (AIDS) or cancer [2]. Cats play an important role in the spread of toxoplasmosis because they are the only animals that excrete resistant oocysts into the environment [3]. In the Republic of Korea, large numbers of stray cats are found roaming residential streets and increasing the risk of public health for animals and humans. The present study was performed to determine the prevalence of T. gondii in a Korean stray cat population, as this frequency is important for determining the epidemiological significance of T. gondii infection.A total of 174 stray cats (75 males and 99 females) were assayed for the prevalence of T. gondii using the latex agglutination test (LAT), ELISA, and diagnostic polymerase chain reaction (PCR).Twenty samples were collected from Gwacheon-si, 82 from Bucheon-si, and 72 from Yangju-si in Gyeonggi-do, Korea. Stray cats were captured as the TNR (trap, neuter, return) program, promoted by the government from April to October 2007. Blood was collected from each cat by cephalic or jugular venipuncture, allowed to clot, and centrifuged for 5 min at 1,800 g, and then the serum was collected and stored at -20℃ until used. The presence of T. gondii antibodies was analyzed using a LAT kit (Eiken Chemical Co., Tokyo, Japan). The procedures described in the manufacturer's instructions were followed accurately. Briefly, serial 2-fold dilutions of the sera were prepared to 1 : 2,048 titer. After mixing the sensitive latex suspension for at least 12 hr, titers measuring 32 or higher were recorded as positive. ELISA was performed as previously described in Choi et al. [4]. The cutoff absorbance of 0.25 was recorded as a positive reaction. For diagnostic PCR, 2 pairs of oligonucleotide primers directed against the B1 gene of T. gondii were used to perform nested PCR [5], using a Maxime PCR premix Kit (Intron, Korea). PCR reactions were cycled 40 times with denaturation at 93℃ for 10 sec followed by annealing at 57℃ for 10 sec and finally an extension step at 72℃ for 30 sec. The amplified DNA was visualized following separation in 2% agarose gels.In LAT, T. gondii antibodies were detected in 14 (8.1%) of 174 Prevalence of Toxoplasma gondii in Stray Cats of Gyeonggi-do, KoreaKorean J Parasitol. Vol. 46, No. 3: 199-201, September 2008 DOI: 10.3347/kjp.2008 199 Abstract: Toxoplasma gondii is an obligate intracellular zoonotic protozoan with a worldwide distribution. It infects humans as well as a broad spectrum of vertebrate hosts. Cats and wild felidae play crucial roles in the epidemiology of toxoplasmo...

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Toxoplasma gondii is an obligate intracellular protozoan that can infect both humans and warm-blooded animals. Among them, cats are the only animal that excretes oocysts into the environment [1]. As recently reported, 47.2% out of 106 stray cats [2] and 13.2% out of 174 stray cats [3] were T. gondii positive by nested PCR assay in Korea. Stray cats have been increasing in Korea roaming residential areas, and this increased the risk of public health hazards. T. gondii strains have been classified into 3 major genotypes (I, II, and III) according to their virulence, and among them, type I strain, such as RH, has been reported to be most virulent. This study is a follow-up of our previous study [3] for genotyping of T. gondii using 23 blood DNA samples of stray cats in Korea, which presented positive reactions by B1 gene amplification.Biodiversity of T. gondii has been reported with genetic variations among isolates from different, and even the same, phenotypes [4]. Usually, T. gondii is categorized as 3 genetic types (I, II, and III) based on polymorphisms in several markers, such as SAG1, SAG2, SAG3, BTUB, GRA6, c22-8, c29-2, PK1, and Apico genes [5,6]. We chose to develop a nested-PCR method based on the polymorphic SAG2 locus, separately amplifying the 5 ′ and 3′ ends of the locus using an Accupower PCR premix Kit (Bioneer Co., Seoul, Korea), and amplifying 241 bp and 221 bp products [7,8]. This gene is ideally suited for rapid genotyping, as it contains multiple lineage-specific polymorphisms [7,9,10]. SAG2 encodes 2 separate forms of the surface tachyzoite protein (p22), that type I (high virulent) and III (avirulent) strains share the same protein alleles, while type II strains (avirulent) have a second, distinct form [5,7]. Sau3A I and Hha I restriction enzymes were used for this PCR-RFLP analysis. Digestion of the 5 ′ amplification products with Sau3A I distinguished allele 3 (type III: includes avirulent strains like VEG and CTG) from alleles 1 and 2 (type I: includes strains like RH and KI-1 which are highly virulent, and type II: includes avirulent strains like PLK and Beverley) [8]. Digestion of the 3′ amplification products with Hha I distinguished allele 2 (type II strains) from alleles 1 and 3 (type I and III strains) [7].RH and KI-1 strains as type I, and ME49 strain as type II, were used for standardization of PCR-RFLP analysis. The representative strain as type III was not prepared because genotyping could be properly discriminated using strains mentioned above. RH strain was kindly provided from Catholic Institute of Parasitic Diseases, Catholic University, and KI-1 and ME49 strains were kindly provided from Department of Parasitology and Tropical Medicine, Seoul National University College of Medicine. RH and KI-1 strains of T. gondii were maintained in BALB/c mice by intraperitoneal inoculation in our laboratory.PCR programs were as follows: The 5′ and 3′ ends of the SAG2 locus were amplified by 5 min of denaturation at 94℃. After Genotype of Toxoplasma gondii from Blood of Stray Cats in Gyeon...