Impact of insecticide-treated bednets and indoor residual spraying in controlling populations of Phlebotomus duboscqi, the vector of Leishmania major in Central Mali

Cheick Amadou Coulibaly, Bourama Traore, Adama Dicko, Sibiry Samake, Ibrahim Sissoko, Jennifer M Anderson, Jesus Valenzuela, Sekou F Traore, Ousmane Faye, Shaden Kamhawi, Fabiano Oliveira, Seydou Doumbia, Cheick Amadou Coulibaly, Bourama Traore, Adama Dicko, Sibiry Samake, Ibrahim Sissoko, Jennifer M Anderson, Jesus Valenzuela, Sekou F Traore, Ousmane Faye, Shaden Kamhawi, Fabiano Oliveira, Seydou Doumbia

Abstract

Background: Cutaneous leishmaniasis (CL) is an endemic neglected tropical disease prevalent in several areas where seasonal malaria transmission is active. We assessed the effect of indoor residual spraying (IRS) and the mass distribution of long-lasting insecticide-treated bednets (LLINs) for malaria control on sand fly population diversity and abundance, and its impact on the risk of Leishmania transmission in the district of Baroueli, endemic for CL in Mali.

Methods: Kemena and Sougoula, two villages in the district of Baroueli, were selected for entomology surveys from March to September 2016 to evaluate sand fly species composition and density, and Leishmania infection rates in the vector Phlebotomus duboscqi. The surveys followed an annual indoor residual spraying and mass distribution of long-lasting insecticide-treated bednets (IRS/LLINs) that began in 2011 for malaria vector control. We also carried out a leishmanin skin test (LST) survey in the two villages to determine the incidence of Leishmania infection in humans living in the endemic area.

Results: A total of 2936 sand fly specimens, 1013 males and 1923 females, were collected and identified from the two villages throughout the study period. Fourteen species, 2 belonging to the genus Phlebotomus and 12 to the genus Sergentomyia, were documented. The genus Sergentomyia constituted 91% of collected sand flies versus 9% for the genus Phlebotomus (P. duboscqi and P. rodhaini). Of those, P. duboscqi was the most abundant, representing 99.6% of the collected Phlebotomus species. In both villages, P. duboscqi was most abundant during the end of dry season (June). The prevalence of Leishmania infection in individual females of P. duboscqi by PCR was 3.5%. After 5 years of the IRS/LLINs, the incidence of Leishmania infection in the human population as measured by LST was 4.2%.

Conclusions: Compared to historical data collected from 2005-2008, a considerable reduction was observed in both sand fly density and prevalence of human Leishmania infection in the villages of Kemena and Sougoula, Baroueli District, following IRS/LLINs. This suggests that IRS/LLINs used for mosquito control also impacts sand fly vectors reducing the incidence of leishmaniasis.

Trial registration: NCT00344084 . Registered: 23 June 2006.

Keywords: Cutaneous leishmaniasis; Indoor residual spraying; LST; Sand fly.

Conflict of interest statement

Ethics approval and consent to participate

The study protocol (NCT00344084, available at https://www.clinicaltrials.gov/ct2/show/NCT00344084/) was approved by the Institutional Review Boards of the National Institute of Allergy and Infectious Diseases (USA) and the University of Bamako (Mali). The study protocol (Protocol # 12–0075) was approved by the Institutional Review Boards (IRB) of the Faculty of Medicine, Pharmacy and Odontostomatology (FMPOS), Bamako, Mali, and of the National Institutes of Allergy and Infectious Diseases (USA). Oral consent from village leaders and signed individual written informed consents were obtained from all adult participants of the study. A parent or guardian of a child participant provided informed consent for enrollment in the study.

Competing interests

The authors declare that they have no competing interests.

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Figures

Fig. 1
Fig. 1
Monthly variation of P. duboscqi females collected indoors and outdoors from March to September 2016. Arrow indicates IRS/LLIN conducted for 2016
Fig. 2
Fig. 2
Repartition of female P. duboscqi according to the repletion status by month from March to September 2016. Arrow indicates IRS/LLIN conducted for 2016
Fig. 3
Fig. 3
Leishmania-specific PCR products from field-collected female P. duboscqi. Lane L: 100 bp ladder; Lane P: positive control (DNA from P. duboscqi experimentally infected with L. major); Lane N: negative control; Lane 1: negative sample; Lanes 2 and 3: positives samples. Predicted band size of the PCR product for L. major is 650 bp

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