Submitted to: Veterinary Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/5/2007
Publication Date: 5/1/2007
Citation: Dubey, J.P., Rajapakse, R.P., Wijesundera, R.R., Sundar, N., Kwok, O.C., Su, C. 2007. Prevalence of Toxoplasma gondii in dogs from Sri Lanka and genetic characterization of the parasite isolates. Veterinary Parasitology. 146:341-346. Interpretive Summary: Toxoplasma gondii is a single-celled parasite of all warm-blooded hosts worldwide. It causes mental retardation and loss of vision in children, and abortion in livestock. Cats are the main reservoir of T. gondii because they are the only hosts that can excrete the resistant stage (oocyst) of the parasite in the feces. Humans become infected by eating undercooked meat from infected animals and food and water contaminated with oocysts. Scientists at the Beltsville Agricultural Research Center and an Univ. in Colombia, South America report first survey of T. gondii infection in dogs in Colombia. The results will be of interest to biologists, parasitologists, and veterinarians.
Technical Abstract: The prevalence of Toxoplasma gondii in 86 unwanted dogs obtained in two batches (36 in batch 1, 50 in batch 2) from Sri Lanka was determined. Antibodies to T. gondii were assayed by the modified agglutination test (MAT) and found in 58 (67.4%) of 86 dogs with titers of 1:20 in seven, 1:40 in four, 1: 80 in 10, 1:160 in 22 , 1: 320 in six, 1: 640 in six, and 1: 1280 or higher in three. Hearts, tongues, and brains (either separately or pooled) of 50 of 51 dogs (24 dogs in batch 1 and 26 in dogs batch 2) with MAT titers of 1:40 were selected for isolation of T. gondii by bioassays in mice. For batch 1 dogs, brains were bioassayed separately and the hearts and tongues were pooled together. For batch 2 dogs, brains, hearts, and tongues were bioassayed separately. For bioassays, canine tissues were digested in pepsin and homogenates were inoculated subcutaneously into mice; the mice receiving canine tissues were examined for T. gondii infection. In all, T. gondii was isolated from 23 dogs (13 batch 1 and 10 batch 2). Interestingly, dog organs varied in their capacity to induce T. gondii infection in mice, muscles producing more positive results than the brain. The 24 T. gondii isolates obtained from 23 seropositive dogs were PCR-RFLP genotyped using polymorphisms at 10 nuclear markers including SAG1, SAG2, SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1, a new SAG2, and an apicoplast marker Apico. Four genotypes were revealed, including three unique genotypes in addition to one belonging to the predominant type III lineage. Mixed infection was found in one dog.