Spatial heterogeneity of malaria vectors and malaria transmission risk estimated using odour-baited mosquito traps

Background Prior to the commencement of a large-scale malaria intervention study on Rusinga Island, western Kenya, intensive baseline surveillance of the mosquito population was performed using odour-baited traps. The survey aimed to determine the relative abundance and species composition of malaria vectors, and to measure seasonal and spatial heterogeneity in populations. Human malaria prevalence was combined with entomological data to provide information about malaria transmission risk before the intervention began. Materials and methods From September 2012 until June 2013, mosquito monitoring took place over successive six-week sampling periods. MM-X traps baited with attractant lures and carbon dioxide were used to collect mosquitoes from inside and outside houses, and a new random sample of 80 households was drawn for each sampling round. During the baseline period, malaria prevalence was measured twice in a randomly selected 10% of the human population. A QuickBird satellite image and digital elevation map were used to describe environmental features of the island. Mosquitoes were initially identified on the basis of morphology and anophelines were processed by PCR to confirm species identifications. Results Odour-baited MM-X traps proved to be a good tool for monitoring malaria vectors inside and outside houses. Using this tool a marked temporal and spatial heterogeneity was described for the malaria vector species Anopheles gambiae s.s., An. arabiensis and An. funestus. Regions of potentially high malaria transmission intensity were identified after mapping the distributions of malaria mosquitoes and Plasmodium-positive persons. Despite studying a range of environmental and topographical features, no strong associations were found between environmental variables and the presence or absence of adult Anopheles. Conclusions Malaria vectors and malaria prevalence are not homogeneously distributed across Rusinga Island; the risk of malaria transmission is therefore greater in some areas than others. The finding that environmental features were not closely associated with adult malaria vector distribution, indicates that other factors, such as house construction or the presence of livestock, may play a more important role in the decision of a female anopheline to approach the domestic environment of a particular house in search of a blood meal. The findings of this study demonstrate how trans-disciplinary data can be integrated to provide a better understanding of mosquito population dynamics and malaria transmission risk. Intensive mosquito monitoring before the commencement of, as well as during, a large-scale malaria intervention study, contributes valuable information which will be used in describing the eventual impact of the intervention

Modification of the Suna Trap for Improved Survival and Quality of Mosquitoes in Support of Epidemiological Studies

Monitoring adult mosquito populations provides information that is critical for assessing risk of vector-borne disease transmission. The recently developed Suna trap was found to be a very effective trap when baited with an attractive odor blend. A modification of this trap was tested to improve its function as a tool for monitoring mosquito populations, including Anopheles coluzzii (An. gambiae sensu stricto molecular form M), Aedes aegypti, and Culex pipiens. The modified Suna trap (Suna-M) was altered by changing the position of the catch bag and the inclusion of a holding chamber in attempts to increase trapping efficacy and enhance the survival of mosquitoes. Each adaptation was tested in a dual-choice setup in a climate-controlled room against the original Suna trap and against 4 standard monitoring methods: the BG-sentinel (BGS), Centers for Disease Control and Prevention (CDC) light trap, Mosquito Magnet X (MM-X) trap, and human landing catch (HLC). No differences in trapping efficacy were observed between the original Suna trap and modified version; however, a version in which the funnel was extended with a box and supplemented with moistened cotton wool increased mosquito survival from 6.5% to 78.0% over 24 h. The HLC and BGS trap outperformed the Suna-M trap, whereas the MM-X and commonly used CDC light trap performed significantly less well than the Suna-M trap in the dual-choice setup. The performance of the Suna-M trap equaled the performance of the original Suna trap and could therefore be used for monitoring purposes. Although the HLC and BGS trap achieved higher catch sizes, the Suna trap has the advantage that it is standardized, does not place humans at risk, and is weather resistant. Field studies should be conducted to confirm that the Suna-M trap, baited with the odor blend, is an efficient and standardized tool to measure both indoor and outdoor disease transmission risk for a range of vector-borne diseases

Tracking the mutual shaping of the technical and social dimensions of solar-powered mosquito trapping systems (SMoTS) for malaria control on Rusinga Island, western Kenya

Background There has been increasing effort in recent years to incorporate user needs in technology design and re-design. This project employed a bottom-up approach that engaged end users from the outset. Bottom-up approaches have the potential to bolster novel interventions and move them towards adaptive and evidence-based strategies. The present study concerns an innovative use of solar-powered mosquito trapping systems (SMoTS) to control malaria in western Kenya. Our paper highlights the co-dependence of research associated with the development of the SMoTS technology on one hand and research for enhancing the sustainable uptake of that very same intervention within the community on the other. Methods During the pre-intervention year, we examined the design, re-design and piloting of a novel technology to generate lessons for malaria elimination on Rusinga Island. Initial ideas about many technological necessities were evaluated and re-designed following feedback from various sources, including technical and social research as well as broader interactions with the social environment. We documented the interlocking of the multiple processes and activities that took place through process observation and document reviews. We analysed the data within the conceptual framework of system innovation by identifying mutual shaping between technical and social factors. Results Our findings illustrate how various project stakeholders including project staff, collaborators, donor, and community members simultaneously pursued interdependent technological transformations and social interests. In the ongoing process, we observed how partial outcomes in the technological domain influenced social events at a later phase and vice versa. Conclusions Looking at malaria intervention projects employing novel technologies as niches that may evolve towards system innovation, helps to reveal interrelations between the various technical and social aspects. Revealing these interrelations requires a different role for research and different perspective on innovation where innovation is more than the technical aspects. This approach therefore requires that research is designed in a way that enables obtaining feedback from both aspects. Keywords: Malaria; Co-evolution; Socio-technical; System innovation; Solar; Mosquito trap; Feedback; Community; Keny