01:50am Thursday 19 October 2017

Parasite treatment failure linked to virus

Parasite infections are common in developing countries. The protozoan parasite Leishmania, for example, infects 12 million people worldwide with leishmaniasis, including in South-Europe.

“All over the world, treatment failure is a major obstacle to the control of infectious diseases like leishmaniasis”, said ITM Prof. Dr. Jean-Claude Dujardin, co-author of  one of the studies, “It is of uppermost importance to understand the factors contributing to this failure to better tackle it.”

The presence of LRV1 increases Leishmaniasis treatment failure

The Leishmania parasite is mainly spread by sand flies.  Depending on the parasite species, symptoms of infection may include large skin lesions, fever, swelling of the spleen and liver, and sometimes disfigurement and death.

The Leishmania parasite sometimes carries a virus called Leishmania virus, or LRV1 for short. In earlier research in animals, scientists found that Leishmania causes more severe infections when the parasite is infected with LRV1. This prompted the researchers to study the effects of the virus in people.

The researchers studied the Leishmania parasite in three South American nations.

The first study was led by Catherine Ronet, PhD, of the University of Lausanne in Switzerland and involved 75 patients of French Guiana. Treatment failed among 30 percent of patients infected with Leishmania that carried the virus, but did not fail in any patients infected with parasites that did not carry the virus.

The second study was led by Stephen Beverley, PhD, of the Washington University School of Medicine in St. Louis, US. American scientists together with colleagues from Peru, Bolivia and Belgium, examined data on 97 patients with leishmaniasis. The researchers found that treatment failed to cure more than 50 percent of patients with parasites infected with the LRV1 virus. However, the failure rate was only 24 percent in patients with parasites that were virus-free.

Implications for Leishmaniasis and other parasite infections

Based on the new research, it may be possible to develop clinical tests to identify virus-infected parasites. This could guide physicians in prescribing a combination of antiparasite and antiviral medications for patients with virus-infected parasites, improving the chances of successful treatment.

“In Peru, leishmaniasis is common in people who work in agriculture and forestry,” said lead author of the Peruvian study, Vanessa Adaui, PhD, of the Cayetano Heredia University in Peru. “Medical resources are often very scarce in the communities where these people work, and although infections typically are not fatal, they can lead to significant scarring, social stigmatization and economic loss.”

The scientists are now investigating how viral infection makes leishmaniasis more difficult to cure. According to Beverley, the parasites infected with the virus may be interacting with patients’ immune systems in a way that disrupts treatment.  Another more likely possibility is that an increase in parasites spurred by the virus may make it more challenging for treatment to completely eliminate the parasites.

“A number of other human parasites bear viral infections that are reminiscent of LRV1 in Leishmania,” Beverley said. “If the viruses’ effects on these other parasites are similar, these findings may open the door to new approaches to treating a range of parasites in the future.”

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