Sentinel Surveillance of Cutaneous Leishmaniasis in Sub-Saharan Africa Based on Non-invasive Molecular Diagnostics: Mapping of Human Cases, Description of Leishamania Species Involved

Leishmaniasis is a parasitosis common to humans and animals (anthropozoonosis), caused by flagellated protozoa called Leishmanias, transmitted by the infective bite of the blood-sucking female of a dipteran insect called sandfly. The parasite reservoirs are wild rodents, humans, dogs. Many species of leishmania can infect humans with a multiplicity of clinical pictures that include visceral, localized, diffuse cutaneous forms and mucocutaneous forms.

Cutaneous leishmaniasis (CL) is a neglected tropical disease whose transmission to humans is based on the bite of sandflies previously contaminated on mammalian reservoirs. Worldwide, more than 200,000 new cases are reported annually. While the Americas and the Near or Middle East are the most important areas, sub-Saharan Africa is also concerned. In a systematic review of the literature published in 2018, Sunyoto et al. identified 54 clinical and epidemiological studies on LC in sub-Saharan Africa. Publications were found in 13 of the 48 countries in sub-Saharan Africa. This review highlighted inconsistent case reporting, clear under-publication and data gaps regarding the exact incidence of CL and its transmission factors, particularly in West Africa.

Indeed, cutaneous leishmaniasis is widely described in East Africa, where many studies have been carried out in Ethiopia, Kenya and Sudan. The presence of Leishmania major and Leishmania aethiopica is well documented, and the dynamics of the infection and its risk factors are studied. In West Africa, on the other hand, the data are more fragmented. The disease is historically reported in the "Cutaneous Leishmaniasis Belt", a Sahelian strip of semi-arid zones extending from Senegal to Sudan. WHO nevertheless estimates that the real number of LC contaminations in the sub-region is 5 to 10 times higher than reported.

Thus, no cases were reported between 2015 and 2017 in the sub-region, which is not very credible in view of the dynamics of declarations during the previous or following years. Over the period 2004-2008, only 155 cases per year were reported, across the following countries: Ghana, Mali, Cameroon, Nigeria, Senegal, DRC and Ivory Coast. No data were available for neighbouring countries with similar ecological contexts, such as Niger, Benin, Guinea or Burkina Faso. The latter is probably the country reporting cases on the most regular basis, with between 500 and 1500 cases/year between 1995 and 2015. Nevertheless, no case was reported between 2007 and 2010, which seems difficult to explain scientifically and again testifies to a lack of diagnosis or reporting.

WHO establishes " country profiles " on the epidemiology of LC for each endemic country and designs regional programmes to control the disease. It should be noted that while East African countries such as Kenya or Ethiopia have a well-documented profile, no profile is available for West African countries. In addition, no regional programme has been set up for sub-Saharan Africa, unlike the Americas, South-East Asia, the Eastern Mediterranean or Europe regions. These absences show how neglected this public health problem is in the African region.