Toxoplasmosis, caused by the protozoan parasite Toxoplasma gondii, is one of the most common parasitic infections of man and other warm-blooded animals. It has been found world-wide from Alaska to Australia. Nearly one-third of humanity has been exposed to this parasite. In most adults it does not cause serious illness, but it can cause blindness and mental retardation in congenitally infected children and devastating disease in immunocompromised individuals.

Toxoplasma gondii is a coccidian parasite which utilizes felids as definitive hosts, and which has an unusually wide intermediate host range. The parasite was initially described by Nicolle and Manceaux in 1908 from the rodent, Ctenodactylus gundi. Infection with T. gondii is one of the most common parasitic infections of man and other warm-blooded animals. It has been found worldwide from Alaska to Australia. Nearly one-third of humanity has been exposed to this parasite; serologic surveys indicate that T. gondii infections are common in wild carnivores, including pigs, bears, felids, fox, raccoons, and skunks. Clinical and subclinical toxoplasmosis has been reported from wild cervids, ungulates, marsupials, monkeys, and marine mammals. Southern sea otter populations have been severely impacted by Toxoplasma infections.

ABSTRACTHelminth parasites ensure their survival by regulating host immunity through mechanisms that dampen inflammation. These properties have recently been exploited therapeutically to treat human diseases. The biocomplexity of the intestinal lumen suggests that interactions between the parasite and the intestinal microbiota would also influence inflammation. In this study, we characterized the microbiota in the porcine proximal colon in response toTrichuris suis(whipworm) infection using 16S rRNA gene-based and whole-genome shotgun (WGS) sequencing. A 21-dayT. suisinfection in four pigs induced a significant change in the composition of the proximal colon microbiota compared to that of three parasite-naive pigs. Among the 15 phyla identified, the abundances ofProteobacteriaandDeferribactereswere changed in infected pigs. The abundances of approximately 13% of genera were significantly altered by infection. Changes in relative abundances ofSuccinivibrioandMucispirillum, for example, may relate to alterations in carbohydrate metabolism and niche disruptions in mucosal interfaces induced by parasitic infection, respectively. Of note, infection byT. suisled to a significant shift in the metabolic potential of the proximal colon microbiota, where 26% of all metabolic pathways identified were affected. Besides carbohydrate metabolism, lysine biosynthesis was repressed as well. A metabolomic analysis of volatile organic compounds (VOCs) in the luminal contents showed a relative absence in infected pigs of cofactors for carbohydrate and lysine biosynthesis, as well as an accumulation of oleic acid, suggesting altered fatty acid absorption contributing to local inflammation. Our findings should facilitate development of strategies for parasitic control in pigs and humans.