In North African countries, cutaneous leishmaniasis transmission has been increasing since the 1980s, with a significant increase in the incidence of cases and a spread of the geographical distribution. The disease currently represents a major public health problem with a productivity gap and an impediment for development, which results in dramatic socioeconomic and psycho-sanitary impacts. The incidence is more than thousands of cases every year in Algeria, Libya, Morocco, and Tunisia. In Egypt, only a few dozen cases per year are reported, mainly in the Sinai Peninsula. Three Leishmania species, associated with distinct eco-epidemiological and clinical patterns, are involved, namely Leishmania infantum, L. major, and L. tropica. However, L. major is by far the most frequent in Algeria, Libya, and Tunisia, with more than 90% of the registered cases. It is mainly encountered in rural areas under semi-arid, arid and Saharan climates. Leishmania tropica is more prevalent in Morocco, reaching 30–40% of isolates in some districts. Much data is still missing concerning the risk factors of the infection and the lesion development, as well as vector and reservoir ecology and behavior. The knowledge of such parameters, following multidisciplinary and integrated approaches, is crucial for better management and control of the disease, that also faces a lack of resources and efficient control measures.

Protozoan parasites of the genus Leishmania cause severe human and veterinary diseases worldwide, termed leishmaniases. A hallmark of Leishmania biology is its capacity to adapt to a variety of unpredictable fluctuations inside its human host, notably pharmacological interventions, thus, causing drug resistance. Here we investigated mechanisms of environmental adaptation using a comparative genomics approach by sequencing 10 new clinical isolates of the L. donovani, L. major, and L. tropica complexes that were sampled across eight distinct geographical regions. Our data provide new evidence that parasites adapt to environmental change in the field and in culture through a combination of chromosome and gene amplification that likely causes phenotypic variation and drives parasite fitness gains in response to environmental constraints. This novel form of gene expression regulation through genomic change compensates for the absence of classical transcriptional control in these early-branching eukaryotes and opens new venues for biomarker discovery.

Localized cutaneous leishmaniasis caused by Leishmania major is polymorphic in its clinical presentation and evolution. Clinical and parasitologic features and disease evolution of 112 Tunisian patients was evaluated. The expression of interleukin (IL)-4, IL-6, IL-10, IL-12 (p40), interferon (IFN)-gamma, and tumor necrosis factor (TNF)-alpha mRNA was analyzed by reverse transcription-polymerase chain reaction in 73 biopsies. Cytokine mRNA expression varied individually over a wide range; TNF-alpha, IL-6, and IFN-gamma were detectable in >90% of lesions, IL-12 and IL-10 in 40% and 70%, respectively, and IL-4 in only 9%. Statistical analysis demonstrated positive association between the level of IL-12 and IFN-gamma and the presence of parasites in the lesions. Unfavorable evolution of the lesions was positively associated with high IL-10, IL-12, and IFN-gamma mRNA expression. These results indicate that an unfavorable clinical outcome was not related to an inadequate Th1 cell response and suggest that the macrophage-activating effect of IFN-gamma may be inhibited by the concomitant expression of IL-10.

No abstract