Controlled release spatial repellent devices (CRDs) as novel tools against malaria transmission: a semi-field study in Macha, Zambia

• Published in: Malaria Journal
• Main Authors: Jennifer C. Stevenson, Limonty Simubali, Twig Mudenda, Esther Cardol, Ulrich R. Bernier, Agustin Abad Vazquez, Philip E. Thuma, Douglas E. Norris, Melynda Perry, Daniel L. Kline, Lee W. Cohnstaedt, Pablo Gurman, Sebastian D’hers, Noel M. Elman
• Format: Article in Journal/Newspaper
• Language: English
• Published: BMC 2018
• Subjects: Malaria; Mosquitoes; Spatial repellent; Semi-field-system; Zambia; Controlled delivery; Arctic medicine. Tropical medicine; RC955-962; Infectious and parasitic diseases; RC109-216; Arctic; Macha
• Online Access: https://doi.org/10.1186/s12936-018-2558-0; https://doaj.org/article/1d8c0e84314748059ca059546b8ecc20

Abstract Background The emergence of mosquitoes that can avoid indoor-deployed interventions, such as treated bed nets and indoor residual spraying, threatens the mainstay of malaria control in Zambia. Furthermore, the requirement for high coverage of these tools poses operational challenges. Spatial repellents are being assessed to supplement these vector control tools, but limitations exist in the residual effect of the repellent and the need for external power or heat for diffusion of the volatiles. Methods A semi-field evaluation of a novel controlled release spatial repellent device (CRD) was conducted in Macha, Zambia. These devices emanate metofluthrin with no need for external power. Devices were deployed in huts within the semi-field system (SFS). Female Anopheles gambiae sensu stricto released within the SFS were trapped overnight by light traps and collected by aspiration the next morning inside and outside of huts to determine the extent of mosquito repellency and the impact on host-seeking and survival. Experiments studied the impact of number of devices as well as the presence of hut occupants. The study was complemented with numerical methods based on computational fluid dynamics to simulate spatial distribution of metofluthrin. Results Presence of CRDs was associated with significant reductions in indoor counts of mosquitoes, regardless of whether huts were occupied or not. Repellency ranged from 15 to 60% compared to huts with no devices. Reducing the number of devices from 16 to 4 had little impact on repellency. When huts were occupied, indoor mosquito host-seeking was higher in the presence of CRDs, whilst survival was significantly reduced. Conclusions This study demonstrated that deployment of as few as four CRDs within a hut was associated with reduced indoor mosquito densities. As would be expected, presence of occupants within huts, resulted in greater indoor catches (both with and without devices). The increased indoor mosquito host-seeking and mortality in huts when devices were ...