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United States Department of Agriculture

Agricultural Research Service


Location: Animal Parasitic Diseases

Title: Isolation and genetic characterization of Toxoplasma gondii from alpaca (Vicugna pacos) and sheep (Ovis aries) grazed on pasture in Virginia

item Dubey, Jitender
item Cassey, Sarah -
item Zajac, Anne -
item Wildeus, Stephan -
item Lindsay, David -
item Verma, Shiv -
item Oliveira, Solange -
item Kwok, Oliver
item Su, Chunlei -

Submitted to: Tropical Animal Health and Production
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 25, 2014
Publication Date: N/A

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 under cooked meat from infected animals and food and water contaminated with oocysts. Toxoplasmosis continues to be a major public health problem. Why some people become sick is largely unknown. The parasite genetics affects pathogenicity. In the present study, authors found that the strains of Toxoplasma isolated from sheep and alpacas grazed same pastures had different genotypes. The results indicate that there is higher genetic diversity among isolates of Toxoplasma in the USA than previously believed. These results will be of interest to biologists, and parasitologists.

Technical Abstract: Muscles (heart, skeletal muscle) of nine alpacas with MAT titers of 1:25 were fed to T. gondii-free cats; the cats did not shed oocysts. Viable T. gondii was isolated from tissues of two of six seropositive alpacas by bioassay in mice. Viable T. gondii was isolated from three of three seropositive sheep by bioassay in mice. All five isolates of T. gondii were avirulent to Swiss Webster outbred mice. Genotyping using cell cultured tachyzoites revealed four genotypes, including one for ToxoDB PCR-RFLP genotype #2 (Type III), one for genotype #3 (Type II variant), one for genotype #170, and two for a new genotype designated as #230. Given that four genotypes were identified from five isolates of T. gondii from alpacas and sheep in the present study, it provides the evidence that there is higher genetic diversity among T. gondii isolates circulating in the USA than previously realized.

Last Modified: 10/24/2014
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