Discrepant prevalence and incidence of Leishmania infection between two neighboring villages in Central Mali based on Leishmanin skin test surveys

Fabiano Oliveira, Seydou Doumbia, Jennifer M Anderson, Ousmane Faye, Souleymane S Diarra, Pierre Traoré, Moumine Cisse, Guimba Camara, Koureissi Tall, Cheick A Coulibaly, Sibiry Samake, Ibrahim Sissoko, Bourama Traoré, Daouda Diallo, Somita Keita, Rick M Fairhurst, Jesus G Valenzuela, Shaden Kamhawi, Fabiano Oliveira, Seydou Doumbia, Jennifer M Anderson, Ousmane Faye, Souleymane S Diarra, Pierre Traoré, Moumine Cisse, Guimba Camara, Koureissi Tall, Cheick A Coulibaly, Sibiry Samake, Ibrahim Sissoko, Bourama Traoré, Daouda Diallo, Somita Keita, Rick M Fairhurst, Jesus G Valenzuela, Shaden Kamhawi

Abstract

Apart from a single report, the last publication of cutaneous leishmaniasis (CL) in Mali dates back more than 20 years. The absence of information on the current status of CL in Mali led us to conduct a cohort study in Kemena and Sougoula, two villages in Central Mali from which cases of CL have been recently diagnosed by Mali's reference dermatology center in Bamako. In May 2006, we determined the baseline prevalence of Leishmania infection in the two villages using the leishmanin skin test (LST). LST-negative individuals were then re-tested over two consecutive years to estimate the annual incidence of Leishmania infection. The prevalence of Leishmania infection was significantly higher in Kemena than in Sougoula (45.4% vs. 19.9%; OR: 3.36, CI: 2.66-4.18). The annual incidence of Leishmania infection was also significantly higher in Kemena (18.5% and 17% for 2007 and 2008, respectively) than in Sougoula (5.7% for both years). These data demonstrate that the risk of Leishmania infection was stable in both villages and confirm the initial observation of a significantly higher risk of infection in Kemena (OR: 3.78; CI: 2.45-6.18 in 2007; and OR: 3.36; CI: 1.95-5.8 in 2008; P<0.005). The absence of spatial clustering of LST-positive individuals in both villages indicated that transmission may be occurring anywhere within the villages. Although Kemena and Sougoula are only 5 km apart and share epidemiologic characteristics such as stable transmission and random distribution of LST-positive individuals, they differ markedly in the prevalence and annual incidence of Leishmania infection. Here we establish ongoing transmission of Leishmania in Kemena and Sougoula, Central Mali, and are currently investigating the underlying factors that may be responsible for the discrepant infection rates we observed between them.

Trial registration: ClinicalTrials.gov NCT00344084.

Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Figure 1. Map of Kemena and Sougoula,…
Figure 1. Map of Kemena and Sougoula, Region of Segou, Mali.
The villages of Kemena and Sougoula are situated between the cities of Bamako and Segou. The insert illustrates the location of Mali in relation to other countries in West Africa.
Figure 2. Prevalence of Leishmania infection by…
Figure 2. Prevalence of Leishmania infection by age group.
Frequency of LST-positive individuals from Kemena (black bars) and Sougoula (white bars) by age group. The numbers in parenthesis represent the total number of individuals in each age group. Asterisks indicate statistical significance (* P

Figure 3. LST reaction size in Kemena…

Figure 3. LST reaction size in Kemena and Sougoula.

Induration size of LST reactions for…

Figure 3. LST reaction size in Kemena and Sougoula.
Induration size of LST reactions for study subjects in Kemena and Sougoula during prevalence and incidence surveys. All measurements over zero were included in the “box and whiskers” plot. The box represents the 25th and 75th percentiles. The median is represented by a solid horizontal line and the mean by a (+). The whiskers of the graph show the 1st percentile to the 99th percentile. Values lower than the first percentile and greater than the 99th percentile are represented by a (•).

Figure 4. Spatial distribution of LST-positive individuals.

Figure 4. Spatial distribution of LST-positive individuals.

Combined distribution of LST-positive individuals (red circles) during…

Figure 4. Spatial distribution of LST-positive individuals.
Combined distribution of LST-positive individuals (red circles) during 2007 and 2008 relative to number of inhabitants per household (yellow circles) in the village of Kemena (A) and Sougoula (B). Diameters of yellow and red circles are proportional to the number of individuals in each location.
Figure 3. LST reaction size in Kemena…
Figure 3. LST reaction size in Kemena and Sougoula.
Induration size of LST reactions for study subjects in Kemena and Sougoula during prevalence and incidence surveys. All measurements over zero were included in the “box and whiskers” plot. The box represents the 25th and 75th percentiles. The median is represented by a solid horizontal line and the mean by a (+). The whiskers of the graph show the 1st percentile to the 99th percentile. Values lower than the first percentile and greater than the 99th percentile are represented by a (•).
Figure 4. Spatial distribution of LST-positive individuals.
Figure 4. Spatial distribution of LST-positive individuals.
Combined distribution of LST-positive individuals (red circles) during 2007 and 2008 relative to number of inhabitants per household (yellow circles) in the village of Kemena (A) and Sougoula (B). Diameters of yellow and red circles are proportional to the number of individuals in each location.

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