One in five people treated for a serious form of leishmaniasis in Nepal relapse after a year. The finding, published in Clinical Infectious Diseases last month, is “an alarming signal” for campaigns to eliminate the neglected disease, say researchers.
Leishmaniasis, which is caused by the parasitic microorganism Leishmania donovani and spread by female sandflies (Phlebotomus argentipes), is endemic in 88 countries, of which 72 are developing, according to the World Health Organization (WHO).
The disease causes skin ulcers, swelling of spleen and liver, and erosion of the mucous linings of the nose, mouth and throat, and can be fatal if left untreated. Nine out of ten cases of the most severe form, visceral leishmaniasis, also known as kala-azar, arise in Bangladesh, Brazil, India, Nepal or Sudan.
The orally administered drug miltefosine emerged as the treatment of choice a decade ago, taking over from injections of the highly toxic, antimony-based drug sodium stibogluconate, which had started showing failure rates of 65% in India’s northern state of Bihar.
But reports are now emerging of miltefosine failure, which scientists worry will narrow down the pipeline of drugs available for treatment.
In the latest study, a team of researchers from Belgium, Nepal and the Netherlands identified 187 cases of visceral leishmaniasis in Nepal, of whom 120 were treated with miltefosine. Six months after treatment with miltefosine, 10% of cases had relapsed; after a year, that had doubled to 20%.
All patients responded well to treatment at first, but cure rates dropped from 82.5% six months after treatment to 73.3% after 12 months. Relapse was most common in children under 12 years old.
The cause of the relapses is unknown: they were not attributable to fresh infections; to co-infection with HIV, which reduces the host’s immunity; to low drug quality; to poor adherence to the treatment regime; or to drug resistance in the parasite.