News Release

Human impacts on Toxoplasma gondii diversity

Peer-Reviewed Publication

Proceedings of the National Academy of Sciences

Researchers report that the domestication of crops and animals may have created conditions for some strains of the parasite Toxoplasma gondii to dominate, leading to lower genetic diversity of the parasite in North America than in South America. The parasite T. gondii can spread to humans from other animal species, and both diversity and virulence of the pathogen are higher in South America than in the Northern Hemisphere. Chunlei Su and colleagues simulated T. gondii life cycles in domestic and wild environments and traced the origins of the Type II strain of T. gondii, common in North America. The results suggest that the development of agriculture and animal domestication decreased animal diversity among agricultural societies and established the domestic cat/mouse transmission cycle of T. gondii, exerting selective pressure that favors the transmission of parasites with reduced virulence in domesticated environments. The authors suggest that strains with intermediate virulence can dominate in domestic life cycles and balance host mortality with the ability to infect animals previously infected with a less virulent strain. According to the authors, the relative absence of such anthropogenic effects in areas such as the Amazon rainforest preserves the diversity and high virulence of T. gondii, which may be increasingly encountered as humans encroach into wild environments.

Article #17-22202: "Human impact on the diversity and virulence of the ubiquitous zoonotic parasite Toxoplasma gondii," by E. Shwab et al.

MEDIA CONTACT: Chunlei Su, University of Tennessee, Knoxville, TN; tel: 865-974-4015; e-mail: <csu1@utk.edu>

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