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ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Animal Parasitic Diseases Laboratory » Research » Publications at this Location » Publication #346878

Research Project: Detection and Control of Foodborne Parasites for Food Safety

Location: Animal Parasitic Diseases Laboratory

Title: A partition of Toxoplasma gondii genotypes across spatial gradients and among host species, and decreased parasite diversity towards areas of human settlement in North America

Author
item Jiang, Tiantian - University Of Tennessee
item Shwab, Keats - University Of Tennessee
item Martin, Robbie - University Of Tennessee
item Gerhold, Richard - University Of Tennessee
item Rosenthal, Benjamin
item Dubey, Jitender
item Su, Chunlei - Non ARS Employee

Submitted to: International Journal for Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/1/2018
Publication Date: 3/23/2018
Citation: Jiang, T., Shwab, K., Martin, R., Gerhold, R., Rosenthal, B.M., Dubey, J.P., Su, C. 2018. A partition of Toxoplasma gondii genotypes across spatial gradients and among host species, and decreased parasite diversity towards areas of human settlement in North America. International Journal for Parasitology. 48(8):611-619. https://doi.org/10.1016/j.ijpara.2018.01.008.
DOI: https://doi.org/10.1016/j.ijpara.2018.01.008

Interpretive Summary: Toxoplasma gondii counts among the most consequential food-borne parasites, and although the parasite occurs in a wide range of wild and domesticated animals, farms may constitute a specific and important locus of transmission. If so, parasites in animals that inhabit agricultural landscapes might be suspected as harboring genetically distinctive parasite types. To better understand landscape effects pertinent to this parasite’s transmission, we compared the genetic variation in isolates from farm-bound animals, free-roaming animals (with wider home range on or near farms) and wildlife. In addition, parasite genotype distribution in different animal species was analyzed. We observed no absolute limitation of any of five major genotypes to any one habitat, but genetic diversity was greater in free-roaming than in farm-bound animals. The genotype composition of parasites in wildlife differed from those in farm-bound and free-roaming animals. Furthermore, parasite genotypes differed among host species. We conclude that T. gondii genotype distributions are influenced by the spatial landscape and host species composition, and parasites are least diverse on farms to which certain types may have adapted. These findings reframe our understanding of the exchange of parasites into and out of livestock, and will help farmers, veterinarians, and epidemiologists manage the risk to food safety imposed by various routes of parasite transmission.

Technical Abstract: Toxoplasma gondii counts among the most consequential food-borne parasites, and although the parasite occurs in a wide range of wild and domesticated animals, farms may constitute a specific and important locus of transmission. If so, parasites in animals that inhabit agricultural landscapes might be suspected as harboring genetically distinctive parasite types. To better understand landscape effects pertinent to this parasite’s transmission, we compiled and analyzed existing genotypic data of 623 samples from animals across a proximity gradient from anthropized environment to the wilderness in North America. To facilitate such analysis, T. gondii isolates were divided into those from: (1) Farm-bound animals (with the most limited home range on farms); (2) Free-roaming animals (with wider home range on or near farms); and (3) Wildlife. In addition, parasite genotype distribution in different animal species was analyzed. We observed no absolute limitation of any of five major genotypes to any one habitat; however, the frequency of four genotypes decreased across the gradient from farm-bound group, to free-roaming group, then the wild, whereas a fifth genotype increased along that gradient. Genetic diversity was greater in free-roaming than in farm-bound animals. The genotype composition of parasites in wildlife differed from those in farm-bound and free-roaming animals. Furthermore, parasite genotypes differed among host species. We conclude that T. gondii genotype distributions are influenced by the spatial landscape and host species composition, and parasite diversity decreases towards anthropized environment, elucidating facts which may influence transmission dynamics and zoonotic potential in this ubiquitous but regionally variable parasite.