New treatments for Visceral Leishmaniasis

Guest blog by Dr Manica Balasegaram, a physician who is the head of the leishmaniasis clinical programme at the Drugs for Neglected Diseases initiative .

A recent report by Médecins Sans Frontières (MSF) of an outbreak of visceral leishmaniasis (VL) in southern Sudan¹ comes at a time when an increasing focus is being put on the control and elimination of neglected diseases. However, this outbreak raises the question of how far along we really are in reaching such targets.

VL (also known as kala azar) is one of the deadliest parasitic diseases in the world, with an estimated half a million new cases each year. Spread by the bites of sandflies, VL severely affects the liver, spleen, and bone marrow, and if left untreated is almost always fatal. Yet the disease remains largely unknown in the developed world.

The control of VL, particularly in the anthroponotic areas of transmission (south Asia and east Africa), has focused on vector control and treatment. In terms of treatments, VL is fairly well served in comparison with other neglected diseases. There are several drugs available, including antimonials (eg, sodium stibogluconate or glucantime), amphotericin B, parmomomycin, and miltefosine (the only available oral drug against the disease). However, all these treatments have various problems, including cost, toxicity, long treatment courses, and low feasibility in the field setting. To achieve the objective of elimination, a tailor-made drug for the disease that only would require a few pills of a very cheap (a few dollars), safe, and effective treatment is needed.

Nonetheless, considerable efforts have recently been made to improve options for patients. On the development side, pivotal trials on combinations of drugs (such as sodium stibogluconate & paromomycin, AmBisome & paromomycin, AmBisome & miltefosine, miltefosine & paromomycin; data in publication) and on a single dose AmBisome have recently been completed in both Africa and Asia.² The results of these trials indicate good safety and efficacy and these treatments could be available for use next year. There is also ongoing research looking at promising potential candidates for clinical development. The goal of such research is to develop a safe, short course (7 day) oral treatment that can be used at the most basic healthcare level. These investments could pay off in the near future, since it is possible that a clinical candidate might be available for development within the next 1–2 years.

This all sounds very exciting, but there are a couple of major issues. Firstly, drug development does not equate to drug implementation. While resources are required and indeed have been invested in research, it is paramount that more resources are dedicated towards roll-out of treatment to ensure that patients get access to these life-saving drugs. This is particularly relevant in regions such as southern Sudan, where the recent outbreak has been reported. The fact that MSF are so actively involved in treating VL patients in several countries is an illustration in itself that insufficient resources are being invested by both governments and donors (both private and public) in control and implementation activities, including case detection, treatment, surveillance, and prevention. There have been some signs of improvement, particularly in south Asia, where a regional commitment has been made between India, Nepal, and Bangladesh to eliminate the disease. However, more efforts need to filter down into field level so that sufficient equipment, drugs, and trained personnel are made available to control the disease.

Another major issue is that VL, like so many neglected diseases, is very much a disease of neglected populations; specifically groups that are poor, marginalised, and living in rural, peri-conflict, or unstable environments.

The further impoverishing effect of VL is now also well documented. It is therefore questionable that we can ever truly eliminate neglected diseases without first making considerable improvements to the lives of the populations in endemic areas. A recent study I read looking at risk factors for VL in India concluded that “improving housing conditions for the poor has the potential to reduce VL incidence”.³ The implication is that the long-term solution to tackling these types of diseases perhaps lies beyond the scope of research and medicine, and that a serious effort needs to be made at a political, social, and economic level to tackle the eternal pandemics of poverty and inequity. In the meantime, the rest of us should continue our day jobs and try to find more mundane, and ‘less ambitious’ solutions.

1  MSF increases response to kala azar outbreak in South Sudan. http://www.msf.org.uk/kala_azar_south_sudan_20100824.news

http://www.doctorswithoutborders.com/news/article.cfm?id=4693&cat=field-news&ref=news-index (Aug 25, 2010)

2. Sundar S, Chakravarty J, Agarwal D, Rai M, Murray HW. Single-dose liposomal amphotericin B for visceral leishmaniasis in India. N Engl J Med 2010; 362: 504–12.

3  Singh SP, Hasker E, Picado A, et al. Risk factors for visceral leishmaniasis in India: further evidence on the role of domestic animals. Trop Med Int Health 2010; 15: 29–35.