Visceral leishmaniasis, also called kala-azar, strikes 400,000 people every year and kills around 1 in 10 of its victims. The leishmania parasite, Leishmania donovani, has proven difficult to treat, in part because a large percentage of patients who take the drug of choice, miltefosine, relapse after treatment, coming down with the same disease all over again. Scientists have long suspected that drug resistance was behind the failure of miltefosine, but that's not so, according to the authors of a study in mBio this week. The study reveals that parasites in patients who relapse after leishmaniasis treatment have a greater infectivity than parasites from patients who were treated successfully. They are essentially a worse, more dangerous form of the parasite.
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