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‘Asexual’ Chagas parasite found to sexually reproduce

The parasite that causes Chagas disease, which had largely been thought to be asexual, has been shown to reproduce sexually after scientists uncovered clues hidden in its genomic code.

That’s the finding of new research, published by a team of scientists from an international group of institutions that includes the Infectious and Tropical Disease Institute at the Ohio University Heritage College of Osteopathic Medicine.

Trypanosoma cruzi is the single-celled parasite responsible for Chagas disease, which is found mostly in Latin America. Around 8 million people are infected by the disease, which can cause irreversible damage to the heart and digestive tract.

Chagas is primarily spread by insects known as Triatominae, or “kissing bugs,” but can also be transmitted by food contaminated with T. cruzi. While some medication can cure patients if given early enough, medication is less effective once the disease is established.

In new research published Sept. 3 in Nature Communications, scientists have sequenced the whole genome of Trypanosoma cruzi and resolved 30 years of heated debate to show that it can indeed be sexually active. This could have important implications for treating the disease and controlling its spread.

Institutions involved in the study, “Meiotic sex in Chagas disease parasite Trypanosoma cruzi,” included the University of Glasgow, Pontifical Catholic University of Ecuador, the Infectious and Tropical Disease Institute at Ohio University’s Heritage College of Osteopathic Medicine, the London School of Hygiene and Tropical Medicine, the Institute of Tropical Medicine Antwerp and Karolinska Institutet Biomedicum Stockholm.

“Chagas Disease in Ecuador is a killer, destroying lives and livelihoods,” said Mario Grijalva, Ph.D., director of ITDI and the lead investigator in Ecuador for the research. “Our study is an important step toward understanding how to control infections and limit spread.”

By studying a large group of parasites found in a small area in Ecuador and sequencing the whole genome of those they found, the researchers were able to spot the tell-tale signatures sexual activity leaves in the genes.

Lead author of the research, Dr. Philipp Schwabl from the University of Glasgow, said: “There has been a lot of argument among scientists about whether T. cruzi is sexual or not. It turns out people weren’t looking in the right places.

“We sampled and analysed, in unprecedented detail, the parasites found in a small geographic area in Ecuador. Remarkably, we discovered that some groups of parasites can be highly sexual. However, it also seems other groups of parasites from very nearby sites can behave very differently — seemingly completely abstinent.

“At the moment, we have no idea why”

Dr. Martin Llewellyn, UK senior scientist on this study, said: “Through analyzing the genetic code, we now know that these parasites do have sex; however, we still can’t pinpoint the exact stage of their life that this happens in. Our hypothesis is that this is happening when the parasites are inside the insect that spreads Chagas disease. Confirming that is the next step.”

The work was funded by the Division of Microbiology and Infectious Diseases, the National Institute of Allergy and Infectious Diseases and the National Institutes of Health (DMID/NIAID/NIH) grants, the NIH-Fogarty Global Infectious Disease Training Program, the Pontifical Catholic University of Ecuador and the Scottish Universities Life Sciences Alliance.

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