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. 2025 Mar 25;25(1):405.
doi: 10.1186/s12879-025-10733-9.

Xenomonitoring as an epidemiological tool supporting post-stop surveillance of albendazole-ivermectin mass drug distribution in the Bougouni-Yanfolila evaluation unit, Sikasso, Mali, in 2023

Lamine Soumaoro  1 , Housseini Dolo  2 , Yaya Ibrahim Coulibaly  2 , Siaka Yamoussa Coulibaly  2 , Salif Seriba Doumbia  2 , Moussa Sangaré  2 , Abdallah Amadou Diallo  2 , Abdoul Fatah Diabaté  2 , Michel Emmanuel Coulibaly  2 , Ibrahima Dolo  2 , Massitan Dembélé  3 , Alpha Seydou Yaro  4 , Thomas Nutman  5
Affiliations

Xenomonitoring as an epidemiological tool supporting post-stop surveillance of albendazole-ivermectin mass drug distribution in the Bougouni-Yanfolila evaluation unit, Sikasso, Mali, in 2023

Lamine Soumaoro et al. BMC Infect Dis. .

Abstract

Introduction: Mali and Guinea share a border and are both endemic for lymphatic filariasis (LF). However, their progress towards eliminating this disease varies. Mali is currently in the LF transmission assessment survey phase (TAS), while Guinea continues to implement mass drug administration (MDA). As the populations of these two countries are closely related, and vectors are present, the emergence of LF is theoretically possible in the Bougouni-Yanfolila evaluation unit (EU). This XenoFil study, which combines xenomonitoring and serosurveillance in health facilities, was used as a surveillance tool to assess LF transmission. The aim is to detect the emergence of LF in cross-border areas within the Bougouni-Yanfolila EU, after the third LF transmission assessment survey (TAS3).

Method: In the Bougouni-Yanfolila EU, we conducted a cross-sectional study to collect mosquitoes in the villages and blood samples from 6 years old and above (≥ 6 years old). In June, August 2022, and January 2023, we conducted three entomological studies in two ecologically distinct villages. The Ifakara type C tent trap (IFAKARA), the gravid trap, and indoor Pyrethrum spray catches were used to collect mosquitoes. For qPCR, mosquito of the same species was sorted into pools of twenty for molecular analysis using qPCR. The infection rate / the parasite prevalence was generated by the PoolScreen® 2 software. Trained local health workers performed serological surveys using filariasis test strips.

Results: In. the two study villages, we collected a total of 4,732 mosquitoes, of which 989 belonged to the species Anopheles gambiae s.l. and 3,743 to species of the genus Culex sp. A total of 264 pools were formed, with the genus Culex spp. accounted for 79.92% (211/264), while the genus Anopheles represented 20.08% (53/264). In June 2022, only one pool (0.53%) of Culex spp. tested positive [95% CI: 0.01-2.89]. Positive Anopheles pools were absent. The blood of ten of the 2056 individuals had positive results [0.49% (10/2056)]. Among the positives, one belonged to 6-7 years, two to that of 8-17 years, and seven to that of 18 years and older. Of the positive volunteers, 0.6% (6/996) were from Yanfolila's border health region. The average cost of XenoFil (entomology combined with serology) is 5,656,244 CFA francs (US$9070), and TAS has an average cost of 6,366,450 CFA francs (US$10209) in a survey conducted in one evaluation unit.

Conclusions: The new XenoFil approach proved to be an easy, effective, and relatively cheaper method for integrated LF surveillance in rural areas. From the perspective of integrated LF monitoring, XenoFil is needed for scaling up to other EU.

Keywords: Anopheles gambiae S.l; Culex spp; Lymphatic filariasis; Guinea; Mali; Serosurveillance; Xenomonitoring.

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Conflict of interest statement

Declarations. Ethics approval and consent to participate: The Ethics Committee (EC) of the University of Sciences, Techniques and Technologies of Bamako approved the protocol under the number 2022/ 294/EC/USTTB. In this study, oral informed consent was administered. All people included in this study were informed verbally and clearly of the blood sampling, the risks and the benefits of the study. Only participants who voluntarily agreed to be sampled took part in the study, and no external pressure was exerted on volunteers. For all three mosquito collection methods, the team obtained verbal consent from villagers working as vector collectors with the research team, as well as from the owners of the rooms visited for mosquito collection. All participants were free to discontinue their participation at any time. In compliance with the Helsinki declaration, our protocol was submitted to and approved by an ethics committee. Consent for publication: During the initial study visits, details of the study’s objectives and implementation phases were clearly explained to the various village chiefs in a series of meetings, so that they would be informed and engaged as beneficiaries of the results, which would help the national program to improve the quality of lymphatic filariasis surveillance to rapidly detect any re-emergence of the disease in their areas bordering the country. Their verbal consent was obtained for: - The sharing of reports with the head of the national lymphatic filariasis elimination program and the chief medical officer of the two health districts, as well as with the health managers of the health centers in the study area. - Publication of the final report and articles with all stakeholders (from national to very peripheral levels, using appropriate media). - Presentations of results at national and international conferences and relevant meetings to share results widely for better use and impact. Competing interests: The authors declare no competing interests. Clinical trial: Not applicable.

Figures

Fig. 1
Fig. 1
Map showing study sites in the Bougouni-Yanfolila Evaluation Unit
Fig. 2
Fig. 2
Map of the Bougouni-Yanfolila Evaluation Unit showing health areas with positive and negative volunteers
See this image and copyright information in PMC

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