Parasites

Breaking the species barrier

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Science  30 Aug 2019:
Vol. 365, Issue 6456, pp. 879
DOI: 10.1126/science.365.6456.879-a

The ubiquitous protist parasite Toxoplasma gondii infects many species but only develops sexually in cats.

PHOTO: DPA PICTURE ALLIANCE/ALAMY STOCK PHOTO

The protozoan parasite Toxoplasma gondii is found in most mammals and is spread by ingestion of contaminated food and water. It is a health risk to humans because it can form brain cysts and cause life-changing complications during pregnancy. Despite this parasite's ability to infect many mammals, it can only complete its life cycle in felids, including domestic cats. Martorelli di Genova et al. sought to understand the basis for the specificity of the sexual stages for the gut epithelium of cats. Using cat gut organoids, they found that the parasite's sexual stages are stimulated to develop by the plant fat linoleic acid. Cats uniquely lack the enzyme needed for linoleic acid digestion, delta-6-desaturase. To test whether intact linoleic acid acts as a parasite signal, mice were given a chemical treatment to inhibit their desaturase, then fed linoleic acid and infected. T. gondii promptly initiated sexual development and the mice shed infectious oocysts in their feces 6 days later.

PLOS Biol. 17, e3000364 (2019).

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