Eave ribbons treated with the spatial repellent, transfluthrin, can effectively protect against indoor-biting and outdoor-biting malaria mosquitoes

Abstract

BackgroundLong-lasting insecticide-treated nets and indoor residual spraying protect against indoor-biting and indoor-resting mosquitoes but are largely ineffective for early-biting and outdoor-biting malaria vectors. Complementary tools are, therefore, needed to accelerate control efforts. This paper describes simple hessian ribbons treated with spatial repellents and wrapped around eaves of houses to prevent outdoor-biting and indoor-biting mosquitoes over long periods of time.MethodsThe eave ribbons are 15 cm-wide triple-layered hessian fabrics, in lengths starting 1 m. They can be fitted onto houses using nails, adhesives or Velcro, without completely closing eave-spaces. In 75 experimental nights, untreated ribbons and ribbons treated with 0.02%, 0.2%, 1.5% or 5% transfluthrin emulsion (spatial repellent) were evaluated against blank controls using two experimental huts inside a 202 m2 semi-field chamber where 500 laboratory-reared Anopheles arabiensis were released nightly. Two volunteers sat outdoors (one/hut) and collected mosquitoes attempting to bite them from 6 p.m. to 10 p.m. (outdoor-biting), then went indoors and slept under bed nets, beside which CDC-light traps collected mosquitoes from 10 p.m. to 6.30 a.m. (indoor-biting). To assess survival, 200 caged mosquitoes were suspended near the huts nightly and monitored for 24 h thereafter. Additionally, field tests were done in experimental huts in a rural Tanzanian village to evaluate treated ribbons (1.5% transfluthrin). Here, indoor-biting was assessed using window traps and Prokopack® aspirators, and outdoor-biting assessed using volunteer-occupied double-net traps.ResultsIndoor-biting and outdoor-biting decreased > 99% in huts fitted with eave ribbons having ≥ 0.2% transfluthrin. Even 0.02% transfluthrin-treated ribbons provided 79% protection indoors and 60% outdoors. Untreated ribbons however reduced indoor-biting by only 27% and increased outdoor-biting by 18%, though these were non-significant (P > 0.05). Of all caged mosquitoes exposed near treated huts, 99.5% died within 24 h. In field tests, the ribbons provided 96% protection indoors and 84% outdoors against An. arabiensis, plus 42% protection indoors and 40% outdoors against Anopheles funestus. Current prototypes cost ~ 7USD/hut, are made of widely-available hessian and require no specialized expertise.ConclusionTransfluthrin-treated eave ribbons significantly prevented outdoor-biting and indoor-biting malaria vectors and could potentially complement current tools. The technique is simple, low-cost, highly-scalable and easy-to-use; making it suitable even for poorly-constructed houses and low-income groups.

Opinions of key stakeholders on alternative interventions for malaria control and elimination in Tanzania

“…SP can be based on a variety of botanical products and chemical compounds, such as citronella, transfluthrin and metofluthrin [27,52]. They can be delivered in different formats, such as mosquito coils, repellent-treated clothing, repellent sandals (Finda et al unpublished), kerosene lamps [53], and eave ribbons [27,28,54]. Compared to widely available topical repellents, some SP can provide longlasting repellency, requiring minimal participation from the users malaria prevalence.…”

“…Several complementary vector control interventions are currently being discussed as possible candidates to accelerate the malaria elimination efforts [12]. Examples include: (a) larval source management (LSM), including larviciding and environmental management [13,14], (b) topical repellents for personal protection [15,16], (c) mass drug administration with endectocides such as ivermectin [17,18], (d) use of mosquito modification techniques, either to suppress or replace vector populations [19,20], (e) outdoor targeting of male mosquitoes through insecticide-spraying of mosquito swarms [21][22][23], (f ) housing improvement measures such as better window screening and improved house designs [24][25][26], (g) spatial repellents able to protect multiple individuals over wide areas [27,28], (h) attractive toxic sugar baits targeting sugar-seeking mosquitoes [29,30], and (i) mosquito-killing fungal spores and toxins [31,32].…”

Creating mosquito-free outdoor spaces using transfluthrin-treated chairs and ribbons

“…Similarly, the hessian ribbons were prepared as previously described by Mmbando et al [36]. Each ribbon had 15 cm width and 10 m length, and were also made locally at the MozzieHouse.…”

Bionomics of Anopheles Arabiensis from Mamfene in KwaZulu-Natal (South Africa): An Area of High Malaria Transmission in the Province

“…Killeen [3] also indicates that the control of the larval stages of the mosquito life cycle can play a signi cant role in curtailing transmission in areas with residual malaria. Current malaria control interventions are being affected by changing mosquito feeding and resting behaviour with mosquito feeding taking place earlier in the evening (before the host retires indoors) and outdoors (to avoid insecticides) [17]. The WHO World Malaria Report [1] shows that there have been major increases in the burden of disease in countries in southern Africa that have been targeting elimination.…”