Ecological niche modelling for predicting the risk of cutaneous leishmaniasis in the Neotropical moist forest biome

A major challenge of eco-epidemiology is to determine which factors promote the transmission of infectious diseases and to establish risk maps that can be used by public health authorities. The geographic predictions resulting from ecological niche modelling have been widely used for modelling the future dispersion of vectors based on the occurrence records and the potential prevalence of the disease. The establishment of risk maps for disease systems with complex cycles such as cutaneous leishmaniasis (CL) can be very challenging due to the many inference networks between large sets of host and vector species, with considerable heterogeneity in disease patterns in space and time. One novelty in the present study is the use of human CL cases to predict the risk of leishmaniasis occurrence in response to anthropogenic, climatic and environmental factors at two different scales, in the Neotropical moist forest biome (Amazonian basin and surrounding forest ecosystems) and in the surrounding region of French Guiana. With a consistent data set never used before and a conceptual and methodological framework for interpreting data cases, we obtained risk maps with high statistical support. The predominantly identified human CL risk areas are those where the human impact on the environment is significant, associated with less contributory climatic and ecological factors. For both models this study highlights the importance of considering the anthropogenic drivers for disease risk assessment in human, although CL is mainly linked to the sylvatic and peri-urban cycle in Meso and South America. © 2019 Chavy et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited

Interleukin (IL)–13 Is the Predominant Th2 Cytokine in Localized Cutaneous Leishmaniasis Lesions and Renders Specific CD4 + T Cells Unresponsive to IL‐12

International audienceSemiquantitative reverse transcription-polymerase chain reaction analysis of leishmania lesion cytokine profile showed a Th2 cytokine expression pattern, as reflected by interleukin (IL)-4 and IL-13 mRNA expression. There was a predominance of IL-13 in most lesions from patients with American localized cutaneous leishmaniasis caused by Leishmania guyanensis. IL-13 production by peripheral blood mononuclear cells in response to specific leishmania antigens was confirmed in these patients. The absence of the second chain of the IL-12 receptor (IL-12Rbeta2) mRNA expression in lesions and the presence of specific IgE and IgG4 in some serum samples demonstrated the functional role of these Th2 cytokines. IL-13, unlike IL-4, rendered specific T cells unresponsive to IL-12 by inhibiting the expression of the IL-12Rbeta2 chain. These data establish the crucial role of IL-13 in human cutaneous leishmaniasis

De la récolte à la mise en fûts

Beau livre Préface de Serge Patient (1934- ), écrivain et poète, lauréat du prix Carbet 2001De la récolte à la mise en fût

High Intralesional Interleukin‐10 Messenger RNA Expression in Localized Cutaneous Leishmaniasis Is Associated with Unresponsiveness to Treatment

International audienceThe intralesional expression of cytokines (interleukin [IL]-4, IL-13, IL-10, and interferon-gamma) was analyzed in 65 patients with localized cutaneous leishmaniasis due to Leishmania guyanensis before specific treatment with pentamidine isethionate. The local expression of IL-10 was significantly higher in patients who responded poorly to treatment than in patients whose lesions were regressing. When an IL-10 level >10 (ratio of the concentration of IL-10 [pg/microL] to that of beta-actin [pg/microL]) was used as an indicator of treatment failure, the sensitivity of this test was 78.6, and the specificity was 72.5. Thus, high intralesional expression of IL-10 might predict a poor response to conventional treatment

Using capillary electrophoresis to identify Anopheline species in routine sampling sites

International audienceAbstract In the Anopheles genus, various mosquito species are able to transmit the Plasmodium parasites responsible for malaria, while others are non‐vectors. In an effort to better understand the biology of Anopheles species and to quantify transmission risk in an area, the identification of mosquito species collected in the field is an essential but problematic task. Morphological identification requires expertise and cannot be checked after processing samples in a destructive treatment, while sequencing of numerous samples is costly. Here, we introduce a method of Species identification via Simple Observation Coupled with Capillary Electrophoresis Technology (SOCCET). This molecular technique of species identification is based on precise determination of ITS2 length combined with a simple visual observation, the colour of mosquito hindleg tip. DNA extracted from field‐collected Anopheles mosquitoes was amplified with universal Anopheles ITS2 primers and analysed with a capillary electrophoresis device, which precisely determines the size of the fragments. We defined windows of amplicon sizes combined with fifth hind tarsus colour, which allows discrimination of the major Anopheles species found in our collections. We validated our parameters via Sanger sequencing of ITS2 amplicons. Using the SOCCET method, we characterised the composition of Anopheles populations in five locations of French Guiana, where we detected a total of nine species. Anopheles braziliensis and Anopheles darlingi were detected in four locations each and represented 13 and 67% of our samples, respectively. The SOCCET method can be particularly useful when working with routine sampling sites with a moderate species diversity, that is, when the number of local species is too high to define species‐specific primers but low enough to avoid individual ITS2 sequencing. This tool will be of interest to evaluate local malaria transmission risk and this approach may be further implemented for other mosquito genera

Leishmania naiffi and lainsoni in French Guiana: Clinical features and phylogenetic variability.

In French Guiana, five species are associated with Cutaneous Leishmaniasis (CL). Though infections with Leishmania guyanensis, L. (V.) braziliensis and L. (L.) amazonensis have been extensively described, there are few available clinical and genetic data on L. (V.) lainsoni and L. (V.) naiffi. We determined the clinical and epidemiological features of all cases of CL due to L. (V.) naiffi and L. (V.) lainsoni diagnosed in French Guiana between 2003 and 2019. Phylogenetic analysis was performed by sequencing a portion of HSP70 and cyt b genes. Five cases of L. naiffi and 25 cases of L. lainsoni were reported. Patients infected by L. (V.) lainsoni were usually infected on gold camps, mostly along the Maroni river (60%), while L. naiffi was observed in French patients infected on the coast (100%). A high number of pediatric cases (n = 5; 20%) was observed for L. (V.) lainsoni. A mild clinical course was observed for all cases of L. (V.) naiffi. HSP70 and cyt b partial nucleotide sequence analysis revealed different geographical clusters within L. (V.) naiffi and L. (V.) lainsoni but no association were found between phylogenetic and clinical features. Our data suggest distinct socio-epidemiological features for these two Leishmania species. Patients seem to get infected with L. (V.) naiffi during leisure activities in anthropized coastal areas, while L. (V.) lainsoni shares common features with L. (V.) guyanensis and braziliensis and seems to be acquired during professional activities in primary forest regions. Phylogenetic analysis has provided information on the intraspecific genetic variability of L. (V.) naiffi and L. (V.) lainsoni and how these genotypes are distributed at the geographic level

A novel mosquito species identification method based on PCR and capillary electrophoresis

In the Anopheles genus, various mosquito species are able to transmit Plasmodium parasites responsible for malaria, while others are non-vectors. In an effort to better understand the biology of Anopheles species and to quantify transmission risk in an area, the identification of mosquito species collected on the field is an essential but problematic task. Morphological identification requires expertise, well-preserved specimens and high-quality equipment, and it does not allow any subsequent verification when samples are later used in a destructive treatment. Moreover, it involves physical manipulations that are not compatible with experiments requiring fast sampling and processing of specimens, hence species identification is often based on DNA sequencing of reference genes or region such as the Internal Transcribed Spacer 2 (ITS2) region of nuclear ribosomal DNA. Sequencing ITS2 for numerous samples is costly, but the design of species-specific PCR primers is not always possible when local species diversity is high. Here, we introduce a molecular technique of species identification based on precise determination of ITS2 length combined with a simple visual observation, the color of mosquito hindleg tip. DNA extracted from field-collected Anopheles mosquitoes was amplified with universal Anopheles ITS2 primers and analyzed with a capillary electrophoresis device, which precisely determines the size of the fragments. We defined windows of amplicon sizes combined with fifth hind tarsus color, which allow to discriminate the major Anopheles species found in our collections. We validated our parameters via Sanger sequencing of the ITS2 amplicons. This method can be particularly useful in situations with a moderate species diversity, i.e. when the number of local species is too high to define species-specific primers but low enough to avoid individual ITS2 sequencing. This tool will be of interest to evaluate local malaria transmission risk and this approach may further be implemented for other mosquito genera

In Vitro Sensitivity of Cutaneous Leishmania Promastigote Isolates Circulating in French Guiana to a Set of Drugs.

International audienceAnti-leishmaniasis drug resistance is a common problem worldwide. The aim of this study was to inventory the general in vitro level of sensitivity of Leishmania isolates circulating in French Guiana and to highlight potential in vitro pentamidine-resistant isolates. This sensitivity study was conducted on 36 patient-promastigote isolates for seven drugs (amphotericin B, azithromycin, fluconazole, meglumine antimoniate, miltefosine, paromomycin, and pentamidine) using the Cell Counting Kit-8 viability test. The IC50 values obtained were heterogeneous. One isolate exhibited high IC50 values for almost all drugs tested. Pentamidine, which is the first-line treatment in French Guiana, showed efficacy at very low doses (mean of 0.0038 μg/mL). The concordance of the in vitro pentamidine results with the patients' clinical outcomes was 94% (K = 0.82)