Spatial analysis of Leishmania donovani exposure in humans and domestic animals in a recent kala azar focus in Nepal.

SUMMARY: Visceral leishmaniasis (VL) is a major public health problem in the Indian subcontinent where the Leishmania donovani transmission cycle is described as anthroponotic. However, the role of animals (in particular domestic animals) in the persistence and expansion of VL is still a matter of debate. We combined Direct Agglutination Test (DAT) results in humans and domestic animals with Geographic Information System technology (i.e. extraction maps and scan statistic) to evaluate the exposure to L. donovani on these 2 populations in a recent VL focus in Nepal. A Poisson regression model was used to assess the risk of infection in humans associated with, among other factors, the proportion of DAT-positive animals in the proximities of the household. The serological results showed that both humans and domestic animals were exposed to L. donovani. DAT-positive animals and humans were spatially clustered. The presence of serologically positive goats (IRR=9.71), past VL cases (IRR=2.62) and the proximity to a forest island dividing the study area (IRR=3.67) increased the risk of being DAT-positive in humans. Even if they are not a reservoir, domestic animals, and specially goats, may play a role in the distribution of L. donovani, in particular in this new VL focus.

Longlasting insecticidal nets for prevention of Leishmania donovani infection in India and Nepal: paired cluster randomised trial.

OBJECTIVE: To test the effectiveness of large scale distribution of longlasting nets treated with insecticide in reducing the incidence of visceral leishmaniasis in India and Nepal. DESIGN: Paired cluster randomised controlled trial designed to detect a 50% reduction in incidence of Leishmania donovani infection. SETTING: Villages in Muzaffarpur district in India and Saptari, Sunsari, and Morang districts in Nepal. PARTICIPANTS: 13 intervention and 13 control clusters. 12 691 people were included in the analysis of the main outcome (infection), and 19 810 were enrolled for the secondary (disease) end point. INTERVENTION: Longlasting insecticidal nets (treated with deltamethrin) were distributed in the intervention clusters in December 2006. MAIN OUTCOME MEASURES: Infection was determined by direct agglutination test at 12 and 24 months after the intervention in those who had negative results (titre <1:1600) at baseline. The effect estimate was computed as the geometric mean of the risk ratios for seroconversion for each cluster pair (net/no net), with its 95% confidence interval. Formal tests of effect of no intervention were obtained with a paired t test. RESULTS: There was no significant difference in the risk of seroconversion over 24 months in intervention (5.4%; 347/6372) compared with control (5.5%; 345/6319 people) clusters (risk ratio 0.90, 95% confidence interval 0.49 to 1.65) nor in the risk of clinical visceral leishmaniasis (0.99, 0.46 to 1.40). Adjustment for covariates did not alter these conclusions. CONCLUSIONS: There is no evidence that large scale distribution of longlasting insecticidal nets provides additional protection against visceral leishmaniasis compared with existing control practice in the Indian subcontinent. The observed effect was small and not significant, though the confidence intervals did not exclude a 50% change in either direction. TRIAL REGISTRATION: Clinical Trials NCT 2005-015374.

The epidemiology and control of leishmaniasis in Andean countries

Revisa o conhecimento atual sobre a epidemiologia da leishmaniose na Venezuela, Colômbia, Equador, Peru e Bolívia, países nos quais a doença é endêmica, tanto nos Andes quanto na Amazônia. Os vetores flebótomos pertencem a vários subgêneros e ao grupo Verrucarum. A maioria dos casos de infecçäo humana é causada pelos parasitas Leishmania do subgênero Viannia. As infecçöes humanas por Leishmania provocam lesöes cutâneas, com uma minoria de infecçöes por L. (Viannia) levando à leishmaniose mucocutânea. Tanto a leishmaniose visceral quanto a leishmaniose cutânea difusa säo raras. Em cada país, parte significativa da transmissäo de Leishmania ocorre no intra ou peridomicílio, muitas vezes próximo à lavoura de café ou cacau. Näo se sabe ao certo quais säo os hospedeiros reservatórios para os ciclos de transmissäo doméstica. Discute-se a carga da doença provocada pela leishmaniose na regiäo, chamando atençäo para os coeficientes de incidência e para a variabilidade dos sintomas. Tal informaçäo fornecerá uma base racional, visando priorizar os recursos voltados para o controle da doença e selecionar esquemas terapêuticos. Descreve também a variaçäo na ecologia da transmissäo, delineando as variáveis que poderiam afetar a definiçäo de estratégias preventivas.