Location: Animal Parasitic Diseases LaboratoryTitle: Phylogeography of Toxoplasma gondii points to a South American origin
|BERTRANPETIT, EMILIE - Hospital And University Center Of Limoges|
|JOMBART, THIBAUT - Imperial College|
|PARADIS, EMMANUEL - University Of Montpellier|
|PENA, HILDA - Universidad De Sao Paulo|
|SU, CHUNLEI - University Of Tennessee|
|MERCIER, AURELIEN - Hospital And University Center Of Limoges|
|DEVILLARD, SEBASTIEN - University Of Lyon|
|AIZENBERG, DANIEL - Hospital And University Center Of Limoges|
Submitted to: Infection, Genetics and Evolution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/21/2016
Publication Date: 3/1/2017
Citation: Bertranpetit, E., Jombart, T., Paradis, E., Pena, H., Dubey, J.P., Su, C., Mercier, A., Devillard, S., Aizenberg, D. 2017. Phylogeography of Toxoplasma gondii points to a South American origin. Infection, Genetics and Evolution. 48:150-155.
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 oocyst. Why some people become ill and even die from toxoplasmosis whereas others remain asymptomatic is largely unknown. The genetic characteristics of T. gondii strains are considered a factor in the pathogenesis on clinical disease. The underlying mechanism for the parasite virulence is also not fully understood. Clinical toxoplasmosis in congenitally infected children is the highest in Brazil. In the present study authors propose that T. gondii spread from South America to other nations, probably through rodents and mice during the human trade. The burden of disease is the highest. These results will be useful for parasitologists and biologists.
Technical Abstract: Toxoplasma gondii, a protozoan found ubiquitously in mammals and birds, is the etiologic agent of toxoplasmosis, a disease causing substantial Public Health burden worldwide, including about 200,000 new cases of congenital toxoplasmosis each year. Clinical severity has been shown to vary across geographical regions, with South America exhibiting the highest burden. Unfortunately, the drivers of these heterogeneities are still poorly understood, and the geographical origin and historical spread of the pathogen worldwide are currently uncertain. A worldwide sample of 168 T. gondii isolates gathered in 13 populations was sequenced for five fragments of genes (140 single nucleotide polymorphisms from 3,153 bp per isolate). Phylogeny based on Maximum likelihood methods with estimation of the time to the most recent common ancestor (TMRCA) and geostatistical analyses were performed for inferring the putative origin of T. gondii. We show that extant strains of the pathogen likely evolved from a South American ancestor, around 1.5 million years ago, and reconstruct the subsequent spread of the pathogen worldwide. This emergence is much more recent than the appearance of ancestral T. gondii, believed to have taken place about 11 million years ago, and follows the arrival of felids in this part of the world. We posit that an ancestral lineage of T.g ondii likely arrived in South America with felids and that the evolution of oral infectivity through carnivorism and the radiation of felids in this region enabled a new strain to outcompete the ancestral lineage and undergo a pandemic radiation.