Seasonal malaria vector and transmission dynamics in western Burkina Faso

Abstract

Background In the context of widespread mosquito resistance to currently available pesticides, novel, precise genetic vector control methods aimed at population suppression or trait replacement are a potentially powerful approach that could complement existing malaria elimination interventions. Such methods require knowledge of vector population composition, dynamics, behaviour and role in transmission. Here were characterized these parameters in three representative villages, Bana, Pala and Souroukoudingan, of the Sudano-Sahelian belt of Burkina Faso, a region where bed net campaigns have recently intensified. Methods From July 2012 to November 2015, adult mosquitoes were collected monthly using pyrethroid spray catches (PSC) and human landing catches (HLC) in each village. Larval habitat prospections assessed breeding sites abundance at each site. Mosquitoes collected by PSC were identified morphologically, and then by molecular technique to species where required, to reveal the seasonal dynamics of local vectors. Monthly entomological inoculation rates (EIR) that reflect malaria transmission dynamics were estimated by combining the HLC data with mosquito sporozoite infection rates (SIR) identified through ELISA-CSP. Finally, population and EIR fluctuations were fit to locally-collected rainfall data to highlight the strong seasonal determinants of mosquito abundance and malaria transmission in this region. Results The principal malaria vectors found were in the Anopheles gambiae complex. Mosquito abundance peaked during the rainy season, but there was variation in vector species composition between villages. Mean survey HLC and SIR were similar across villages and ranged from 18 to 48 mosquitoes/person/night and from 3.1 to 6.6% prevalence. The resulting monthly EIRs were extremely high during the rainy season (0.91–2.35 infectious bites/person/day) but decreased substantially in the dry season (0.03–0.22). Vector and malaria transmission dynamics generally tracked seasonal rainfall variations, and the highest mosquito abundances and EIRs occurred in the rainy season. However, despite low residual mosquito populations, mosquitoes infected with malaria parasites remained present in the dry season. Conclusion These results highlight the important vector control challenge facing countries with high EIR despite the recent campaigns of bed net distribution. As demonstrated in these villages, malaria transmission is sustained for large parts of the year by a very high vector abundance and high sporozoite prevalence, resulting in seasonal patterns of hyper and hypo-endemicity. There is, therefore, an urgent need for additional vector control tools that can target endo and exophillic mosquito populations. Electronic supplementary material The online version of this article (10.1186/s12936-019-2747-5) contains supplementary material, which is available to author...

Motivations and expectations driving community participation in entomological research projects: Target Malaria as a case study in Bana, Western Burkina Faso

“…The density of Anopheles mosquitoes is typically highest in September-October and lowest around January-February. The extent of bed net coverage is high, although many of the nets are old [16,17]. Virtually all the youths in the village do regular gardening as an incomegenerating activity, yet this activity is insu cient to meet their needs.…”

A novel age-structured mosquito model for assessing the mechanisms behind vector control success

“…Our current model doesn't take account of seasonal changes in vector population sizes and behaviours, which is known to have a substantial effect on malaria transmission [42]. However, as the relative benefit of the three measures is independent of vector population size, our comparisons remain valid.…”

Motivations and expectations driving community participation in entomological research projects: Target Malaria as a case study in Bana, Western Burkina Faso

“…The density of Anopheles mosquitoes is typically highest in September-October and lowest around January-February. The extent of bednet coverage is high, although many of the nets are old [16,17]. Virtually all the youths in the village do regular gardening as an income-generating activity, yet this activity is insufficient to meet their needs.…”

“…No genetically modified mosquitoes were released in Bana, or indeed in any other location in Burkina Faso, during the period when the research presented in this paper was conducted. The only mosquito releases that took place were in the course of mark-releaserecapture studies involving conventional mosquitoes [17]. The overarching goal of these deliberative activities was to obtain and sustain a 'social license to operate' in Bana [33][34][35].…”

“…In Western Burkina Faso, these field entomological research has been underway since July 2012 and communities in the area have been actively involved in a variety of investigational activities, including Human Landing Catch sampling of mosquito populations, location and sampling of swarms, egg surveys, insecticide spray catches [16], and mark-release-recapture experiments [17,18].…”