Fig 1.
A schematic illustration of key features and work flows for the three experiments comprising this study.
Fig 2.
Schematic illustration of the design of experiments 1 and 2.
Schematic (A) and photographic (B) illustration of the arrangement of human landing catches (HLC) by users of treated or untreated sacking strips and non-users sitting in exposure free M traps at specific randomized distances and angles at which a human baited trap was placed. The HLC captures conducted by the users of treated and untreated strips were used to quantify personal protection provided by the treated strips (Fig 1, Objective 1.1). Captures with nearby M traps occupied by participants lacking any treated or untreated strip were used to quantify the degree to which proximity to a protected strip user might decrease (Fig 1, Objective 1.2) or increase (Fig 1, Objective 1.3) biting exposure, over a range of distances varying from 2 to 40 meters. The same phenomenon was assessed at a distance of 80 meters by comparing the number of mosquitoes caught by users of untreated strips on nights when the other user at the other catching station in the same site used a treated strip with the numbers caught when the nearby strip user had an untreated strip.
Fig 3.
Duration of relative protection conferred by treated hessian strips against biting mosquitoes over time.
Weekly aggregate crude estimates of protection against all three of the most common mosquito taxa present over the course of a 2.5 year period following initial transfluthrin treatment of the sacking strips (Fig 1, Experiment 1, Objective 1.1). Estimated mean weekly daily mean temperature is also plotted to illustrate how cold spells were initially observed to be associated with reduced protective efficacy.
Fig 4.
Differential effect of temperature on efficacy of hessian strips against biting mosquitoes.
Effect of daily mean temperature for the day preceding each night of experimentation upon efficacy of hessian strips treated with 10ml of transfluthrin, over the first year post-treatment (Fig 1, Experiment 1, Objective 1.1). Each data point represents the mean relative rate of mosquito capture through human landing catches conducted by users of treated strips, averaged within each one degree temperature range category.
Fig 5.
Effect of treated hessian strips upon human exposure to mosquitoes as a function of distance.
Estimated proportional protection of users and nearby non-users of treated strips (Fig 1, Experiment 1, Objectives 1.2 and 1.3). This analysis was restricted to data from the first year of experiment 1 (Fig 3), for which strips were treated with the maximum 10ml dose.
Fig 6.
Protective efficacy of different doses of transfluthrin treated hessian strips.
Relative proportional protection of users of strips treated with different doses of transfluthrin (Fig 1, Experiment 2, Objective 2).
Fig 7.
Examples of the rapidly diversifying array of physical formats for hessian strip transfluthrin emanators derived from the prototype evaluated here.
A: The previously described lead prototype emanator [17,18] which was evaluated in detail in this manuscript. B: A second, more convenient “flag” prototype [31], with the fabric strip enclosed in a welded iron frame, leaning up against a user’s chair on her porch. C: The same second flag prototype hanging in a public bar [31]. D: The same second prototype placed up against an end user’s front door, to prevent house entry by Culex spp. mosquitoes which rest upon the door and then enter when it is opened in the morning. E: The third and latest, foldable, self-standing prototype, in which the hessian strip is protected from moisture on the ground, and users are protected from physical contact with the active ingredient, by sandwiching it within a wire mesh cover with wide margins.