Leishmaniasis: current situation and new perspectives

https://doi.org/10.1016/j.cimid.2004.03.004Get rights and content

Abstract

Leishmaniasis represents a complex of diseases with an important clinical and epidemiological diversity. Visceral leishmaniasis (VL) is of higher priority than cutaneous leishmaniasis (CL) as it is a fatal disease in the absence of treatment. Anthroponotic VL foci are of special concern as they are at the origin of frequent and deathly epidemics (e.g. Sudan). Leishmaniasis burden remains important: 88 countries, 350 million people at risk, 500,000 new cases of VL per year, 1–1.5 million for CL and DALYs: 2.4 millions. Most of the burden is concentrated on few countries which allows clear geographic priorities. Leishmaniasis is still an important public health problem due to not only environmental risk factors such as massive migrations, urbanisation, deforestation, new irrigation schemes, but also to individual risk factors: HIV, malnutrition, genetic, etc… Leishmaniasis is part of those diseases which still requires improved control tools. Consequently WHO/TDR research for leishmaniasis has been more and more focusing on the development of new tools such as diagnostic tests, drugs and vaccines. The ongoing effort has already produced significant results. The newly available control tools should allow a scaling up of control activities in priority areas. In anthroponotic foci, the feasibility of getting a strong impact on mortality, morbidity and transmission, is high.

Résumé

Les leishmanioses représentent un groupe de maladies extrémement diverses tant sur le plan clinique qu'épidémiologique. La leishmaniose viscérale (LV) mérite une attention toute particulière car mortelle en l'absence de traitement. En ce qui concerne la lutte, il convient de s'attaquer prioritairement aux foyers de leishmaniose viscérale anthroponotique, sources d'épidémies fréquentes et mortelles (Soudan). Le poids de la maladie reste considérable: 88 pays, 350 millions de personnes à risque, une incidence annuelle pour la leishmaniose viscérale de 500.000 cas et pour la cutanée de 1 à 1,5 million et enfin des DALYs estimés à 2,4 millions. La majorité des cas se concentrent sur quelques pays. Ce qui facilite la définition de priorités géographiques. La leishmaniose reste un sévère problème de santé publique du fait de l'importance ccroissante des risques liés à l'environnement tels que les migrations, l'urbanisation, la déforestation, les nouveaux schémas d'irrigation mais aussi des risques individuels comme le VIH, la malnutrition et les facteurs génétiques. La leishmaniose fait partie des maladies dont il est nécessaire d'améliorer les outils de lutte. C'est pourquoi la recherche au sein de l'OMS (TDR) a concentré ses efforts sur le développement de nouveaux outils de lutte tels que les tests de diagnostic, les médicaments et les vaccins. Cet effort a déjà abouti à d'importants résultats permettant ainsi d'appliquer, dans les zones prioritaires, les méthodes et stratégies de lutte à une plus grande échelle. Dans les foyers anthroponotiques, on a maintenant la capacité de réduire de façon significative la mortalité, la morbidité et le rique de transmission à l'homme en général.

Introduction

The leishmaniases remain a severe public health problem. The burden is increasing [1]. The perspectives of control are still highly dependent on research progresses to obtain better tools and a more cost-effective strategy for case management and vector control. With valuable field tools, a step by step elimination should become feasible specially in anthroponotic foci where man is the sole reservoir.

Section snippets

Disease manifestations

Clinical forms of leishmaniasis are particularly diverse representing a complex of diseases: visceral leishmaniasis (VL) is usually fatal when untreated, muco-cutaneous (MCL) is a mutilating disease, diffuse cutaneous leishmaniasis (DCL) is a long-lasting disease due to a deficient cellular-mediated immune response and cutaneous leishmaniasis (CL) is disabling when lesions are multiple.

The disease is caused by a parasite belonging to the genus Leishmania. It is spread by the bite of the female

DALYs

The burden of leishmaniasis expressed in disability-adjusted life years (DALYs) is estimated at: 2,357,000 (946,000 for males and 1,410,000 for females) [8].

Morbidity

The leishmaniases cause considerable morbidity and mortality. In man, the disease occurs in at least 4 major forms: cutaneous, diffuse cutaneous, mucocutaneous and visceral.

Current management and control strategies

The main control strategy includes: case finding and treatment, vector control, when feasible and, in zoonotic foci, animal reservoir control. For VL, serological diagnosis is classically based on ELISA, IFAT and Direct agglutination test (DAT), parasitological diagnosis relies on spleen, bone marrow or lymph nodes aspirate. Treatment consists of first-line drugs: the pentavalent antimonials, and second line drugs amphotericin B and amphotericin B in liposomes, the latest restricted to

Persistence of VL burden and lack of attention

The burden is still increasing due to technical and managerial constraints. Currently there is not a real cost-effective control package. There is a clear need to reinforce the screening and the diagnosis of VL in peripheral health structures where patients are treated on the base of clinical suspicion. Usually, there are no facilities to perform and read bone marrow or spleen aspiration in most of the districts hospitals. Screening and diagnosis in such settings should rely on simple tests.

Up

Previous successes in China, Turkmenistan, Uzbekistan

In the past, some eradication programmes were successfully completed when supported by a strong political and financial commitment. For example:

  • Foci of anthroponotic cutaneous leishmaniasis (ACL) of Turkmenistan and Uzbekistan were put under control in 1957 and 1960, respectively, The strategy applied was a combination of early diagnosis through active case detection, systematic treatment, large-scale vector control based on insecticide spraying and intensive urban sanitation including improved

Diagnosis

The new field tests, recently made available, are more accessible than the traditional ones (IFAT and ELISA): rapid strip, dipstick k39 (US$ 1), DAT freeze dried antigen (US$ 3), latex agglutination test for antigen detection in urine(US$ 1,5). It is a great progress but currently the case management strategy depends more on the cost of treatment than on that of testing.

Treatment

Some cost reduction has been obtained during the last 5 years, particularly with the availability on the market of the generic

R&D Agenda

As leishmaniasis mainly affects poor countries, research and development of new diagnostic tools and drugs have been dramatically neglected.

There is a clear need for more investment in field oriented research, to continue improving case management (better use of existing tools and validation of new tools). Simultaneously to the availability of the first oral drug for VL, it is of prime importance to have accurate and practical diagnostic methods available in endemic areas.

Conclusions

The main challenge is to translate new knowledge into cost-effective and affordable control tools (better reagents for diagnosis, new drugs and vaccines) and to improve the patient's accessibility to them. Progress obtained through basic research should be transformed into field achievements.

Increased research and funds are needed for neglected diseases such as leishmaniasis. WHO, together with several other institutions, should approach donors from public and private sectors to convince them

References (21)

There are more references available in the full text version of this article.

Cited by (1826)

View all citing articles on Scopus
View full text