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United States Department of Agriculture

Agricultural Research Service


item Dubey, Jitender
item Gennari, Solange
item Sundar, N
item Vianna Mannola, C
item Bandini, L
item Yai, L
item Kwok, Oliver
item Su, Chun Lee

Submitted to: Journal of Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/1/2006
Publication Date: 1/1/2007
Citation: Dubey, J.P., Gennari, S.M., Sundar, N., Vianna Mannola, C.B., Bandini, L.M., Yai, L.E., Kwok, O.C., Su, C. 2007. Diverse and atypical genotypes identified in Toxoplasma gondii from dogs in São Paulo, Brazil. Journal of Parasitology. 93:60-64.

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. Toxoplasmosis causes mortality in many species of animals in the zoos, especially primates. Scientists at the Beltsville Agricultural Research Center and the University of Sao Paulo, Brazil, South America report genetic characterization of Toxoplasma from dogs from Brazil. The results will be of interest to biologists, parasitologists, and veterinarians.

Technical Abstract: Dogs are considered a potential risk for transmission of Toxoplasma gondii to humans because they can mechanically transmit oocysts to people. The prevalence of T. gondii in 118 unwanted dogs from the São Paulo city, São Paulo state, Brazil, was determined. Antibodies to T. gondii were assayed by the modified agglutination test (MAT), and found in 42 (35.8 %) dogs with titers of 1:20 in 10, 1: 40 in 6, 1: 80 in 5, 1: 160 in 5, 1:320 in 6, 1:640 in 7, and 1:1,280 or higher in 3. Hearts and brains of 36 seropositive dogs were bioassayed in mice, cats or both. Tissues from 20 seropositive dogs were fed to 20 T. gondii-free cats. Feces of cats were examined for oocysts. Toxoplasma gondii was isolated from 15 dogs by bioassay in mice, from the brains alone of 1, from the heart alone of 4, and both brains and hearts of 10. All infected mice from 5 of 15 isolates died of toxoplasmosis during primary infection. Four additional isolates were obtained by bioassay in cats. Genotyping of these 19 T. gondii isolates using polymorphisms at 10 nuclear markers including SAG1, SAG2, SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1 and a new SAG2, and an apicoplast marker Apico revealed 12 genotypes. One isolate had Type III alleles at all 11 loci, and the rest 18 isolates contained the combination of different alleles and were divided into 11 genotypes. The absence of Type II in Brazil was confirmed. The result supports previous findings that T. gondii population is highly diverse in Brazil.

Last Modified: 10/15/2017
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