Eave tubes for malaria control in Africa: a modelling assessment of potential impact on transmission

Abstract

BackgroundNovel interventions for malaria control are necessary in the face of problems such as increasing insecticide resistance and residual malaria transmission. One way to assess performance prior to deployment in the field is through mathematical modelling. Modelled here are a range of potential outcomes for eave tubes, a novel mosquito control tool combining house screening and targeted use of insecticides to provide both physical protection and turn the house into a lethal mosquito killing device.MethodsThe effect of eave tubes was modelled by estimating the reduction of infectious mosquito bites relative to no intervention (a transmission metric defined as relative transmission potential, RTP). The model was used to assess how RTP varied with coverage when eave tubes were used as a stand-alone intervention, or in combination with either bed nets (LLINs) or indoor residual spraying (IRS).ResultsThe model indicated the impact of eave tubes on transmission increases non-linearly as coverage increases, suggesting a community level benefit. For example, based on realistic assumptions, just 30 % coverage resulted in around 70 % reduction in overall RTP (i.e. there was a benefit for those houses without eave tubes). Increasing coverage to around 70 % reduced overall RTP by >90 %. Eave tubes exhibited some redundancy with existing interventions, such that combining interventions within properties did not give reductions in RTP equal to the sum of those provided by deploying each intervention singly. However, combining eave tubes and either LLINs or IRS could be extremely effective if the technologies were deployed in a non-overlapping way.ConclusionUsing predictive models to assess the benefit of new technologies has great value, and is especially pertinent prior to conducting expensive, large scale, randomized controlled trials. The current modelling study indicates eave tubes have considerable potential to impact malaria transmission if deployed at scale and can be used effectively with existing tools, especially if they are combined strategically with, for example, IRS and eave tubes targeting different houses.Electronic supplementary materialThe online version of this article (doi:10.1186/s12936-016-1505-1) contains supplementary material, which is available to authorized users.

Control of Malaria Vector Mosquitoes by Insecticide-Treated Combinations of Window Screens and Eave Baffles

“…These empirical studies ( 43 ) also suggest grounds for optimism regarding the recent theory that combining recently developed, low-technology emanators for airborne pyrethroid vapor ( 44 , 45 ) with complementary nonpyrethroid indoor control measures, such as IRS, WSEBs, or alternative technologies, such as eave tubes ( 46 – 48 ) and entry traps ( 49 ), could coselect for evolutionarily stabilized restoration of physiologic susceptibility and behavioral responsiveness to pyrethroids generally ( 50 ). …”

Empirical and theoretical investigation into the potential impacts of insecticide resistance on the effectiveness of insecticide‐treated bed nets

“…To evaluate the consequences of the lethal and sublethal effects revealed in the empirical studies for overall transmission, we developed a deterministic feeding‐cycle model. The model was similar to others previously used to evaluate transmission‐related metrics for malaria vectors (e.g., Cator, Lynch, Thomas, & Read, ; Waite, Lynch, & Thomas, ). The structure and details are summarized in the Supplementary Information, with parameter estimates given in Table .…”

“…Thus, if RTP = 0, transmission is completely halted, whereas RTP = 1 is equivalent to baseline transmission in the absence of LLINs. If the rate of recruitment to the adult vector population and the size of the human population are both assumed to be unaffected by an intervention, RTP can be assumed to map directly to a proportional change in the entomological inoculation rate (EIR) (Waite et al., ).…”

Integrating Models of Diffusion and Behavior to Predict Innovation Adoption, Maintenance, and Social Diffusion

“…As such, the approach essentially turns the house into a ‘lethal lure’ that not only reduces the entry of mosquitoes but also kills them as they search around the house and attempt to enter via the eave tubes (Sternberg et al, 2016). This mortality is predicted to provide community protection once the coverage of the SET innovation reaches a certain level (i.e., screening alone ought to benefit individual householders, but by killing mosquitoes the benefit of SET should extend also to householders who have not adopted the technology) (Waite, Lynch, & Thomas, 2016). Once installed, the SET innovation requires little upkeep.…”