Arsenic Exposure and Treatment Failure for Visceral Leishmaniasis in India

Dr. Albert Picado, from ISGlobal, has participated in an international study published in PLOS Neglected Tropical Diseases that aims to understand why, in India, certain treatments against visceral leishmaniasis (VL) do not work.

Sodium stibogluconate (SSG) contains antimony, a chemical similar to arsenic, and has been the predominant treatment against VL. However, since the late twentieth century, treatment with SSC has ceased to function in more than half of VL patients in India, resulting in a serious public health problem. The authors of the study speculated that the parasite has developed resistance to treatment with antimony due to chronic exposure to arsenic. Proof of concept for this hypothesis has been validated experimentally in mice. To test the hypothesis in the field, the investigators designed a retrospective study with around one hundred VL patients treated with SSG between 2006 and 2010 in the Bihar region. This region reports the highest number of SSG-resistant VL cases in India.

The aim of the study was to evaluate if arsenic levels and SSG-based treatment outcome are related. The results show there is a tendency to more treatment failure among arsenic exposed patients, although they are not conclusive. They do show however that chronic exposure to arsenic significantly increases the risk of VL mortality. The authors note that the relationship between arsenic exposure and VL mortality deserves further investigation. "The factors associated with SSG treatment failure in India are complex and diverse", explains Dr. Picado, "and arsenic exposure most likely explains only one part of the story".  The study is also a reminder that the environment in which a parasite propagates needs to be considered when assessing reasons of treatment failure and mortality.  

Visceral leishmaniasis, also known as kala-azar in India, is caused by the Leishmania donovani parasite and transmitted by the bite of the sandfly. With 280,000 new clinical cases every year, VL is an important cause of morbidity, mortality and economic loss particularly among the most vulnerable populations and represents a considerable public health problem in India.