Annual Incidence Of Visceral Leishmaniasis Research Articles

In silico identification of human microRNAs pointing centrin genes in Leishmania donovani: Considering the RNAi-mediated gene control.

Leishmaniasis, a parasitic disease caused by different species of the protozoa parasite Leishmania, is a neglected tropical human disease that is endemic in about a hundred countries worldwide. According to the World Health Organization (WHO), the annual incidence of cutaneous leishmaniasis (CL) is estimated to be 0.7-1.2 million cases globally, whereas the annual incidence of visceral leishmaniasis is estimated to be 0.2-0.4 million cases. In many eukaryotic organisms, including human beings and protozoan parasites, centrin genes encode proteins that play essential roles within the centrosome or basal body. Human microRNAs (miRNAs) have been linked to several infectious and non-infectious diseases associated with pathogen-host interactions, and they play the emphatic roles as gene expression regulators. In this study, we used the MirTarget bioinformatics tool, which is a machine learning-based approach implemented in miRDB, to predict the target of human miRNAs in Leishmania donovani centrin genes. For cross-validation, we utilized additional prediction algorithms, namely, RNA22 and RNAhybrid, targeting all five centrin isotypes. The centrin-3 (LDBPK_342160) and putative centrin-5 (NC_018236.1) genes in L. donovani were targeted by eight and twelve human miRNAs, respectively, among 2,635 known miRNAs (miRBase). hsa-miR-5193 consistently targeted both genes. Using TargetScan, TarBase, miRecords, and miRTarBase, we identified miRNA targets and off-targets in human homologs of centrin, inflammation, and immune-responsive genes. Significant targets were screened based on GO terminologies and KEGG pathway-enrichment analysis (Log10p-value >0.0001). In silico tools that predict the biological roles of human miRNAs as primary gene regulators in pathogen-host interactions help unravel the regulatory patterns of these miRNAs, particularly in the early stages of inflammatory responses. It is also noted that these miRNAs played an important role in the late phase of adaptive immune response, inclusively their impacts on the immune system's response to L. donovani.

Modelling spatiotemporal patterns of visceral leishmaniasis incidence in two endemic states in India using environment, bioclimatic and demographic data, 2013-2022.

As of 2021, the National Kala-azar Elimination Programme (NKAEP) in India has achieved visceral leishmaniasis (VL) elimination (<1 case / 10,000 population/year per block) in 625 of the 633 endemic blocks (subdistricts) in four states. The programme needs to sustain this achievement and target interventions in the remaining blocks to achieve the WHO 2030 target of VL elimination as a public health problem. An effective tool to analyse programme data and predict/ forecast the spatial and temporal trends of VL incidence, elimination threshold, and risk of resurgence will be of use to the programme management at this juncture. We employed spatiotemporal models incorporating environment, climatic and demographic factors as covariates to describe monthly VL cases for 8-years (2013-2020) in 491 and 27 endemic and non-endemic blocks of Bihar and Jharkhand states. We fitted 37 models of spatial, temporal, and spatiotemporal interaction random effects with covariates to monthly VL cases for 6-years (2013-2018, training data) using Bayesian inference via Integrated Nested Laplace Approximation (INLA) approach. The best-fitting model was selected based on deviance information criterion (DIC) and Watanabe-Akaike Information Criterion (WAIC) and was validated with monthly cases for 2019-2020 (test data). The model could describe observed spatial and temporal patterns of VL incidence in the two states having widely differing incidence trajectories, with >93% and 99% coverage probability (proportion of observations falling inside 95% Bayesian credible interval for the predicted number of VL cases per month) during the training and testing periods. PIT (probability integral transform) histograms confirmed consistency between prediction and observation for the test period. Forecasting for 2021-2023 showed that the annual VL incidence is likely to exceed elimination threshold in 16-18 blocks in 4 districts of Jharkhand and 33-38 blocks in 10 districts of Bihar. The risk of VL in non-endemic neighbouring blocks of both Bihar and Jharkhand are less than 0.5 during the training and test periods, and for 2021-2023, the probability that the risk greater than 1 is negligible (P<0.1). Fitted model showed that VL occurrence was positively associated with mean temperature, minimum temperature, enhanced vegetation index, precipitation, and isothermality, and negatively with maximum temperature, land surface temperature, soil moisture and population density. The spatiotemporal model incorporating environmental, bioclimatic, and demographic factors demonstrated that the KAMIS database of the national programmme can be used for block level predictions of long-term spatial and temporal trends in VL incidence and risk of outbreak / resurgence in endemic and non-endemic settings. The database integrated with the modelling framework and a dashboard facility can facilitate such analysis and predictions. This could aid the programme to monitor progress of VL elimination at least one-year ahead, assess risk of resurgence or outbreak in post-elimination settings, and implement timely and targeted interventions or preventive measures so that the NKAEP meet the target of achieving elimination by 2030.

Risk factors of visceral leishmaniasis among residents of Baringo County, Kenya

Background: Leishmaniasis is protozoan disease, transmitted by Sandflies. The annual incidence of visceral leishmaniasis in East Africa is between 29,400 and 56,700 cases, accounting for approximately 15% of the global cases. Visceral leishmaniasis is endemic in Baringo County yet the current report on risk factor burden of the disease has not been documented. Objective was to assess risk factors associated with visceral leishmaniasis among residents of Baringo County, Kenya.Methods: Analytical cross sectional study design was conducted in Tiaty and Baringo south sub counties, Baringo County. The study population was 422 households selected through simple random sampling. The data collection tool were questionnaires. Data was analyzed using descriptive statistics, cross tabulations and chi square test of independence. Logistic regression was used to compute odds ratio. Variables with p value of less than 0.05 was considered statistically significant.Results: Findings showed that uneducated were majority (68%), higher number of the population had more than 6 persons per household (70.6%). On occupation, pastoralists were more affected (62.2%), those living in mud and cracked house were more (61.8%) (63.0 %) respectively p&lt;0.01. Daily activity 35.24, p&lt;0.01), sleeping under acacia tree 53.42, p&lt;0.01), sleeping outside the house 112.7, p&lt;0.01), and presence of ant hills nearby homestead 32.42, p&lt;0.01) were individual risk factors significantly associated visceral leishmaniasis.Conclusions: The risk factors increased the exposure of the community to visceral leishmaniasis infection which needs to be addressed through control and prevention measures.

Studies on sand fly fauna and ecological analysis of Phlebotomus orientalis in the highland and lowland foci of kala-azar in northwestern Ethiopia.

BackgroundVisceral leishmaniasis (VL) also known as kala-azar is a growing health problem in Ethiopia with an estimated annual VL incidence between 3700 and 7400. The disease is mainly endemic in northwestern parts of the country. The aim of the current study was to determine the sand fly fauna and ecology of Phlebotomus orientalis in two endemic and ecologically distinct areas of northwestern Ethiopia.MethodsSand flies were collected using CDC light traps, sticky traps and pyrethrum spray catches from peri-domestic, mixed forest, farm field and indoor habitats from both Libo-Kemkem (May 2011-April 2012) and Metema (October 2012-September 2013) districts.ResultsA total of 51,411 sand fly specimens were collected and identified (10,776 from highland and 40, 635 from the lowland areas). Seven species were found in the highland area: two Phlebotomus spp. (P. orientalis and P. rodhaini) and five Sergentomyia species. Whereas 19 species were found in the lowland area: six Phlebotomus (P. orientalis, P. rodhaini, P. bergeroti, P. duboscqi, P. papatasi and P. martini) and 13 Sergentomyia species. Of the Phlebotomus spp., P. orientalis was the predominant species in both the highland (99.9%) and lowland (93.7%) areas. Indoor collections using pyrethrum spray catches and sticky traps indicated that P. orientalis has a strong exophilic and exophagic behaviors in both districts. In both areas, this species showed seasonal occurrence and showing abundance during the dry months (March-May/June) of the year and increasing in numbers till the rain season, when numbers dropped dramatically. Mean density of P. orientalis in the two areas had positive and significant correlation with mean temperature in light trap collections (P<0.05). However, mean density of P. orientalis in the two areas in sticky trap collections had positive and insignificant association with the temperature (P>0.05). Regarding the rainfall pattern, density of P. orientalis had negative and statistically insignificant correlation (for light trap collections for both areas) and significant correlation (for sticky trap collections for lowland area).ConclusionsThe current study indicated the variation in sand fly fauna between the highland and lowland districts, wherein, P. orientalis was found to be the most abundant Phlebotomus species. The study also determined that P. orientalis exhibits distinct seasonality, where its abundance increases during the dry season and disappears when the rainy period starts in both study areas. This entomological observation on the bionomics of P. orientalis provides significant evidence for considering vector control or preventive measures in the areas studied.

Epidemiological characteristics of visceral leishmaniasis in Morocco (1990–2014): an update

Leishmaniases are parasitic diseases frequent in the Mediterranean Basin. Visceral leishmaniasis (VL) is a notifiable parasitic disease that increased in incidence in Morocco over the past few years and has recently emerged in several new foci, causing a public health problem in Morocco. The aim of this study is to describe the spatio-temporal distribution of VL in Morocco between 1990 and 2014 period in order to highlight important features and trends of VL and its epidemiology and to assess whether the activity of the unit reflects the situation of the disease at the national level and whether it could constitute an indicator of public health relevance. Two thousand four hundred and twenty one cases were reported in Morocco between 1990 and 2014 with an average annual reported incidence rate of 0.4 cases per 100.000 inhabitants. Before 1996 the average annual incidence of VL was 50 cases on average. After this date the number of cases increased and then remained stable with around 100–150 cases per year. Children whose age varies between 1 and 4 years old are the most affected with 1327 (74%) of total cases; nevertheless the adult starts to be affected by the disease. In 2000, 65% of positive cases of VL are concentrated at both northern regions: Taza-Al Hoceima- Taounate with 45% of cases, Tanger- Tetouan mainly represented by Chefchaoun with 20% of cases. The Fez-Boulemane region located in the center recorded 12% of cases. Throughout the years the map VL distribution has been progressively changed and spatial spread of the disease to the center is noted in 2007. 2014 has been marked by an even greater extension of the disease to the center and south of Morocco. Nationally in 2014, 34 of 75 provinces and prefectures are affected compared to 2000, when 22 out of 82 provinces and prefectures were affected. Leishmania infantum was identified the causative agent based on species- specific PCR-Lei70 assay. VL remains a sporadically endemic parasitic disease in Morocco with a progressive extension of its range of distribution. Such a situation would relate to the geographical succession of Phlebotomine sand fly vectors, the difficulty of actions against the canine population reservoirs of L. infantum and unfavorable socio-economic factors.

Feasibility of eliminating visceral leishmaniasis from the Indian subcontinent: explorations with a set of deterministic age-structured transmission models

BackgroundVisceral leishmaniasis (VL) is a neglected tropical disease transmitted by sandflies. On the Indian subcontinent (ISC), VL is targeted for elimination as a public health problem by 2017. In the context of VL, the elimination target is defined as an annual VL incidence of <1 per 10,000 capita at (sub-)district level. Interventions focus on vector control, surveillance and on diagnosing and treating VL cases. Many endemic areas have not yet achieved optimal control due to logistical, biological as well as technical challenges. We used mathematical modelling to quantify VL transmission dynamics and predict the feasibility of achieving the VL elimination target with current control strategies under varying assumptions about the reservoir of infection in humans.MethodsWe developed three deterministic age-structured transmission models with different main reservoirs of infection in humans: asymptomatic infections (model 1), reactivation of infection after initial infection (model 2), and post kala-azar dermal leishmaniasis (PKDL; model 3). For each model, we defined four sub-variants based on different assumptions about the duration of immunity and age-patterns in exposure to sandflies. All 12 model sub-variants were fitted to data from the KalaNet study in Bihar (India) and Nepal, and the best sub-variant was selected per model. Predictions were made for optimal and sub-optimal indoor residual spraying (IRS) effectiveness for three different levels of VL endemicity.ResultsStructurally different models explained the KalaNet data equally well. However, the predicted impact of IRS varied substantially between models, such that a conclusion about reaching the VL elimination targets for the ISC heavily depends on assumptions about the main reservoir of infection in humans: asymptomatic cases, recovered (immune) individuals that reactivate, or PKDL cases.ConclusionsAvailable data on the impact of IRS so far suggest one model is probably closest to reality (model 1). According to this model, elimination of VL (incidence of <1 per 10,000) by 2017 is only feasible in low and medium endemic settings with optimal IRS. In highly endemic settings and settings with sub-optimal IRS, additional interventions will be required.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-016-1292-0) contains supplementary material, which is available to authorized users.

Visceral Leishmaniasis: Advancements in Vaccine Development via Classical and Molecular Approaches.

Visceral leishmaniasis (VL) or kala-azar, a vector-borne protozoan disease, shows endemicity in larger areas of the tropical, subtropical and the Mediterranean countries. WHO report suggested that an annual incidence of VL is nearly 200,000 to 400,000 cases, resulting in 20,000 to 30,000 deaths per year. Treatment with available anti-leishmanial drugs are not cost effective, with varied efficacies and higher relapse rate, which poses a major challenge to current kala-azar control program in Indian subcontinent. Therefore, a vaccine against VL is imperative and knowing the fact that recovered individuals developed lifelong immunity against re-infection, it is feasible. Vaccine development program, though time taking, has recently gained momentum with the emergence of omic era, i.e., from genomics to immunomics. Classical as well as molecular methodologies have been overtaken with alternative strategies wherein proteomics based knowledge combined with computational techniques (immunoinformatics) speed up the identification and detailed characterization of new antigens for potential vaccine candidates. This may eventually help in the designing of polyvalent synthetic and recombinant chimeric vaccines as an effective intervention measures to control the disease in endemic areas. This review focuses on such newer approaches being utilized for vaccine development against VL.

Model-based investigations of different vector-related intervention strategies to eliminate visceral leishmaniasis on the Indian subcontinent.

The elimination of infectious diseases requires reducing transmission below a certain threshold. The Visceral Leishmaniasis (VL) Elimination Initiative in Southeast Asia aims to reduce the annual VL incidence rate below 1 case per 10,000 inhabitants in endemic areas by 2015 via a combination of case management and vector control. Using a previously developed VL transmission model, we investigated transmission thresholds dependent on measures reducing the sand fly density either by killing sand flies (e.g., indoor residual spraying and long-lasting insecticidal nets) or by destroying breeding sites (e.g., environmental management).Model simulations suggest that elimination of VL is possible if the sand fly density can be reduced by 67% through killing sand flies, or if the number of breeding sites can be reduced by more than 79% through measures of environmental management.These results were compared to data from two recent cluster randomised controlled trials conducted in India, Nepal and Bangladesh showing a 72% reduction in sand fly density after indoor residual spraying, a 44% and 25% reduction through the use of long-lasting insecticidal nets and a 42% reduction after environmental management.Based on model predictions, we identified the parameters within the transmission cycle of VL that predominantly determine the prospects of intervention success. We suggest further research to refine model-based predictions into the elimination of VL.

Integrated visceral leishmaniasis surveillance system in primary care for children in Meshkin-Shahr district, north-western Islamic Republic of Iran

In 2001 a visceral leishmaniasis (VL) surveillance system was set up for children aged < or = 12 years in the primary health system in Meshkin-Shahr district of Ardebil province, north-western Islamic Republic of Iran. All cases with clinical signs and symptoms of VL and positive by the direct agglutination test were referred for physical examination and treatment. The mean annual incidence of VL decreased significantly from 1.88 before (1985-2000) to 0.77 per 1000 child population after the intervention (2001-07). In a control area with no surveillance, it increased from 0.11 to 0.23 per 1000. Early detection of VL using practical serological tests and timely treatment of cases could decrease the mortality and morbidity rates of VL in endemic areas.

Serological markers for Leishmania donovani infection in Nepal: agreement between direct agglutination test and rK39 ELISA

Visceral leishmaniasis (VL) is an important vector-borne disease caused by Leishmania donovani in the Indian subcontinent. The actual incidence and role of asymptomatic infections in the region are not wellknown. We used the direct agglutination test (DAT) and the rK39 ELISA as L. donovani infection markers in 10 VL endemic villages in Nepal. DAT titre distribution showed two subgroups in the population (infected and non-infected individuals), while rK39 did not. The agreement between both tests was moderate (j = 0.53; 95% CI 0.49–0.57). More research is needed to develop validated markers for Leishmania infection.

Effectiveness and feasibility of active and passive case detection in the visceral leishmaniasis elimination initiative in India, Bangladesh, and Nepal.

This study analyzed the effectiveness of active case detection (ACD) for new visceral leishmaniasis (VL) cases. ACD detection was carried out using house to house screening in Bangladesh and India and by neighborhood screening around index cases in Nepal. The percent increase of new VL cases through ACD compared to PCD was 6.7-17.1% in India; 38.8% in Nepal; and 60% in Bangladesh. The screening effort was high in India and Bangladesh (house to house screening) compared to Nepal (index case screening). The additional cost per new VL case detected varied: $50 to $106 in India; $172 in Bangladesh; $262 in Nepal depending on the type of screening staff, transport and training costs. The estimated annual VL incidence in the ACD arm ranged from 315-383 in India; 109 in Bangladesh, and 43 per 100,000 in Nepal. The additional effort and cost rises as disease incidence declines or PCD improves.

Annual incidence of visceral leishmaniasis in an endemic area of Bihar, India

The study presents the findings of a population-based survey of the annual incidence of visceral leishmaniasis (VL) in the rural areas of one VL-endemic district in Bihar, India. Stratified multi-stage sampling was applied in the selection of blocks, villages, hamlets, and households. We screened 15 178 households (91 000 individuals) in 80 villages in 7 of 27 administrative blocks of the district, East Champaran. We identified 227 VL cases that occurred in the past 12 months: 149 treated individuals who survived, 14 who died from VL, and 64 active cases. The high-incidence stratum had an estimated incidence of 35.6 cases per 10 000 persons per year (90% CI: 27.7-45.7). The annual incidence rate in the medium stratum areas was 16.8 cases per 10 000 (90% CI: 9.3-30.6). The combined annual incidence rate for the high and medium areas combined was 21.9 cases per 10 000 per year, (90% CI: 14.0-34.2). The Government of India's VL elimination goal is to reduce the VL incidence to one case per 10 000 at the sub-district level; thus, a 35-fold reduction will be required in those areas with the highest VL incidence.

The burden of visceral leishmaniasis in South Asia

This supplement presents a collection of studies that were undertaken in India and Nepal on the burden of visceral leishmaniasis (VL), investigating issues related to the epidemiology and economic impact of the disease. Since 2005, the governments of India, Nepal and Bangladesh are engaged in a collaborative effort to control and eliminate visceral leishmaniasis from the Indian subcontinent. With 60% of the global VL burden in South Asia, this disease remains an important public health problem in the region. VL not only leads to tremendous human suffering since untreated cases result in death, but also has a profound impact on the livelihood of affected households (Boelaert et al. 2009). Renewed interest given to VL over the past decade resulted in important innovations in diagnosis and treatment. However, many aspects of the VL burden of disease are still not clear. One of the major challenges for the elimination initiative is the absence of reliable epidemiological surveillance data on VL morbidity and mortality in the region. Without these data it is difficult to assess whether the initiative is achieving its stated goal – the reduction of the annual incidence of VL to <1/10 000 population at the district level in Nepal, and the sub-district and upazila level in India and Bangladesh respectively (World Health Organization 2005) – or whether the various control interventions have their intended effect. The current officially reported figures are obtained through passive case detection in government health services and usually do not include cases detected by the private for-profit sector, which constitutes a majority of the health providers in the Indian subcontinent. These figures therefore largely underestimate the actual number of cases. For example Singh et al. (2006) documented underreporting by a factor of eight in a community development block in Muzaffarpur district in Bihar, India in 2001–2003 and more recently (Singh et al. 2010c) estimated underreporting by a factor of four in Vaishali district, also in Bihar. This ‘decrease’ in underreporting is attributed by some to the effect of the VL elimination initiative and the recent contribution of several not-for-profit NGOs operating in the area with specific VL care programs. Population-based surveys such as those described above provide us with valuable information on local incidence rates, and repeating these surveys over time might allow us to not only monitor progress of the VL elimination initiative, but also to assess the effectiveness of VL control strategies. This supplement includes several populationbased surveys that can shed further light on the true frequency of infection and disease in the region. VL incidence rates (and underreporting) vary greatly between countries (Mondal et al. 2009) as well as between districts and within districts as shown by Das et al. (2010) in this supplement. Moreover, VL cases tend to cluster within certain sections of the village at hamlet level and further at household level (Ahluwalia et al. 2003). Incidence rates can be ten times greater at hamlet level (in the range of 1– 2% per year) than the aggregate figures recorded at district level (in the range of 1–2 per 1000 per year). Some of the work presented in this supplement by Singh et al. (2010b) and Rijal et al. (2010) has documented precisely what the burden is in such so-called ‘hot spots’ at hamlet level in endemic districts. The impact of VL in these affected communities tends therefore to be much stronger than would seem from aggregate figures, because those communities tend to be the most deprived ones, of lowest cast, and lowest economic status (Boelaert et al. 2009). Singh et al. also point to some gender-specific differences in burden of infection, a theme which is under-researched so far, apart from work in Bangladesh (Ahluwalia et al. 2003). Our understanding of the risk factors for VL in SouthAsia has greatly improved in recent years. Identified risk factors have been fairly similar across studies, with the presence of a previous case of kala-azar in the household as the strongest predictor of risk and living conditions as a recurrent theme. Killick-Kenrick coined the term ‘paradise for sandflies’ to describe the housing conditions in endemic villages. Damp earthen floors, mud-plastered walls with cracks, proximity to water bodies, soil littered with organic matter, sleeping on the ground etc. are all linked to poverty as well as to increased exposure to peri-domestic sandflies. Most of the published studies assessed the risk for VL Tropical Medicine and International Health doi:10.1111/j.1365-3156.2010.02564.x

Visceral leishmaniasis elimination programme in India, Bangladesh, and Nepal: reshaping the case finding/case management strategy.

ObjectiveWe sought to estimate visceral leishmaniasis (VL) burden in Bangladesh, India, and Nepal and document care-seeking behaviour for VL to provide baseline information for monitoring the VL elimination program and identify options for improved case finding and management.DesignA cross-sectional study using cluster sampling (clusters being villages) of 4 VL endemic districts was used in order to document all current and existing VL cases over the preceding 12 mo. Extended (in-depth) interviews were conducted in a subsample of households to explore (a) VL-related knowledge, attitudes, and practices of the population; (b) use of VL care by patients; and (c) delay between onset of symptoms, diagnosis, and start of treatment, as well as treatment interruption. Findings were discussed with national program managers and policy makers to develop improved strategies.ResultsScreening for VL was done in 18,933 households (106,425 inhabitants). The estimated annual incidence of VL in the endemic districts was on average 22 times higher than the elimination target of less than one case per 10,000 inhabitants in 2015. This incidence varied widely between study sites, from 9.0 to 29.8 per 10,000 inhabitants. The percentage of newly detected cases through the household screening was high in the districts least covered by health-care services (particularly Rajshahi, Bangladesh, 49%; and to a lesser extent Vaishali in Bihar, India, 32.5%), and much lower in districts with greater availability of VL care (Muzaffarpur, India, 3.8%). On average 267 houses had to be visited, i.e., at least three to four working days per health worker, to identify a new VL (ranging from 1,432 houses in Muzaffarpur, India to only 166 houses in Rajshahi, Bangladesh). Knowledge of the disease and its vectors was good in India and Nepal but poor in Bangladesh (Rajshahi) where very little attention has been given to VL over the last decades. Although all socio-demographic indicators showed high levels of poverty, people in India preferred private medical practitioners for the treatment of VL, whereas in Nepal, and even more in Bangladesh, the public health-care sector was preferred. Delays between onset of symptoms and diagnosis as well as start of treatment was high. Reported non-adherence to treatment was particularly high in the more under-served districts and was mainly due to lack of resources.DiscussionThe findings suggest that (a) house-to-house screening may be useful in highly endemic districts with a poor passive case detection system, but further evidence on case finding adapted to local conditions has to be collected; (b) strengthening the quality of the public health sector is imperative in the three countries, especially in India, with its largely unregulated private-sector provision of VL care.

La aparición de leishmaniasis y el cambio climático

Spatio-temporal modelling of the distributions of the leishmaniases and their sandfly vectors is reviewed in relation to climate change. Many leishmaniases are rural zoonoses, and so there is a foundation of descriptive ecology and qualitative risk assessment. Dogs are widespread reservoir hosts of veterinary importance. Recent statistical modelling has not always produced novel general conclusions, exemplifying the difficulty of applying models outside the original geographical region. Case studies are given for transmission cycles involving both cutaneous and visceral leishmaniasis in the Old World and the Americas. An important challenge is to integrate statistical spatial models based mainly on climate with more explanatory biological models. Ecological niche models pose difficulties because of the number of assumptions. A positive association has been reported between the El Niño cycle and the annual incidence of visceral leishmaniasis in Brazil, but more basic research is needed before tackling other climate-change scenarios, including leishmaniasis emergence in northern Europe.

The impact of highly active antiretroviral therapy (HAART) on visceral leishmaniasis in Spanish patients who are co-infected with HIV.

Clinicians in Madrid have been observing and treating HIV-positive patients with visceral leishmaniasis (VL) for over a decade. As their records cover some of the co-infection cases that occurred before and after highly active antiretroviral therapy (HAART) was introduced into Spain, retrospective analysis of the records has allowed some of the effects of HAART on local VL to be determined. Encouragingly, HAART appears to have decreased the annual incidence of VL among local AIDS cases, from 4.81 cases/100 to just 0.8 case/100 (P <0.0005), a first episode of VL now appearing only when there is obvious HAART failure. Unfortunately, it does not seem to be very good at preventing VL relapses; within 24 months of antileishmanial treatment, 70% of patients who were receiving HAART had such relapses. The mean time between antileishmanial treatment and VL relapse was, however, longer when HAART was used than when it was not (20 v. 13 months). In those receiving HAART, relapses of the VL often occurred despite increasing CD4+ cell counts and undetectable HIV loads, indicating that successful treatment of the viral infection is insufficient to prevent the relapse of the leishmaniasis. These results are in general agreement with other observations made in Spain. VL relapses are possible and even frequent in HIV-positives who have no more than 200 CD4+ cells/microl, but secondary prophylaxis to prevent VL relapses may be safely suspended if a CD4+ count of >200 cells/microl can be maintained using HAART. VL also seems to hamper the immunological recovery of the HIV-positive, although HAART appears to have little effect on the clinical manifestations of VL.

Impact of the El Niño/Southern Oscillation on visceral leishmaniasis, Brazil.

We used time-series analysis and linear regression to investigate the relationship between the annual Niño-3 index from 1980 to 1998 and the annual incidence of visceral leishmaniasis (VL) in the State of Bahia, Brazil, during 1985–1999. An increase in VL incidence was observed in the post-El Niño years 1989 (+38.7%) and 1995 (+33.5%). The regression model demonstrates that the previous year’s mean Niño-3 index and the temporal trend account for approximately 50% of the variance in the annual incidence of VL in Bahia. The model shows a robust agreement with the real data, as only the influence of El Niño on the cycle of VL was analyzed. The results suggest that this relationship could be used to predict high-risk years for VL and thus help reduce health impact in susceptible regions in Brazil.