Investigation of an Outbreak Situation of Cutaneous Leishmaniasis Among Military Personnel in French Guiana (CEFELEISH)

Cutaneous leishmaniasis is endemic in French Guiana and represents 200 to 300 cases per year. Transmission occurs after a sandfly bite, mainly during the rainy season and over almost all of French Guiana. The incidence is, however, greater in forest areas, especially in recently cleared areas. Nevertheless, transmission remains continuous and outbreaks remain rare and little investigated. This study comes following an outbreak signal that occurred in May 2020, after the detection of numerous cases of cutaneous leishmaniasis in military personnel probably contaminated during a training course (Training Center in the Equatorial Forest, CEFE) in the town of Regina. To date, around 40 cases have been detected. This outbreak raises several scientific questions, on the microbiological, clinical and epidemiological level.

From a microbiological point of view, it is not certain whether the occurrence of a large number of cases in a given group over a short period can be attributed to a single leishmania clone or only reflect exposure to a large number of infected sandflies. An L. braziliensis outbreak has been described in naturalists on mission in the Saul region, but it is possible that several species are detected in a larger outbreak. The description of the activities at the origin of the contamination can influence the offending species insofar as the different sandfly species do not use the same reservoirs, are not found in the same ecosystems and do not carry the same species of leishmanias.

Clinically, in the case that many patients are infected after the bite of similar sandflies and under similar conditions, similar clinical manifestations could be expected. It would be interesting to look for variations in terms of the type, number, localization, severity of lesions, and especially of response to treatment, which would reflect the role of factors linked to the host and its immune response. A phylogenetic study would make it possible to compare the strains isolated during this outbreak with other Guyanese isolates from the 2020 rainy season in order to search for a genetic cluster. A comparison can also be made between the strains of the outbreak in order to find a correlation with the clinical severity of certain patients or resistance to first-line treatment (Pentacarinat).

Epidemiologically, the outbreak occurred at a training site already used in previous years, but without such numerous cases being reported. This site sits on 700 hectares of primary forest and has not recently undergone additional development or deforestation. The course of activities and the type of training carried out by the military has not changed this year. A change in environmental conditions and exposure to sandflies therefore does not seem to explain this increase in cases. A capture of sandflies, delayed in relation to the period of contamination, would not allow the question of environmental change to be answered.

On the other hand, looking for behavioral risk factors (clothing, night shower, role played in exercises, type of hammock used, etc.) could provide explanations for the occurrence of infections in some trainees and not in their classmates. A case-control study can therefore be carried out using a questionnaire offered to all course participants over the 1st semester of 2020. The controls will then be participants who have not been infected. A comparison can also be made between the military personnel present in French Guiana during the first half of 2020 and having carried out missions in the forest, by opposing the participants and non-participants of the CEFE, in order to determine whether this course represented an independent risk factor for leishmaniasis. This result would reflect a higher exposure than conventional operations against gold mining, for example.

Investigation of this outbreak would make it possible to take corrective actions in terms of prevention and public health. It would provide a better understanding of the pathophysiological mechanism of contamination (clonal or not) and the consequences in terms of infecting species, clinical severity and expected therapeutic response in the circumstances of grouped cases of cutaneous leishmaniasis.

Retrospective cohort study for the clinical and microbiological part (grouped cases of an outbreak) Case-control section with questionnaires assessing exposure to sandflies National multicenter sample Category 3 Non-Interventional Human Person Research (RIPH 3)