Human Volunteers

The MET is composed of four wooden panel frames measuring 35 × 35 cm, arranged to form a square cavity into which human volunteers’ legs are placed (Fig. 2c). The panels hold sets of vertical parallel stainless steel wires spaced 5 mm apart, which are electrically connected to a 24 V battery-powered stable direct current (DC) power source, thereby creating an electric potential between the wires, which is sufficient enough to kill mosquitoes trying to pass through the wires, but without destroying the specimen, as observed with previous prototypes [68 (link)]. The power is supplied at low output, which is sufficient to kill mosquitoes on contact but poses no harm if accidentally contacted by volunteer. This combination of voltage with current setting was identified through pilot laboratory experiments using insectary-reared An. gambiae and An. arabiensis specimens with an a prior minimum kill probability threshold of 80 % [80 ]. The MET prototype used was modified to improve upon shortcomings reported in an earlier version which included the tendency to short circuit and weak physical stability [68 (link)]. Specific changes were: (1) introduction of hinges to secure the four angles of the main frame (Fig. 2a), and (2) better alignment of grid wires into the frame using grooves which minimized the possibility of opposing wires contacting each other and short circuiting. During mosquito trapping, each MET unit was placed on a 2 m × 2 m wooden frame platform placed on a white sheet (Fig. 2c) which made it easier for collectors to see the electrocuted mosquitoes that dropped on the floor. The four legs of the platform were placed in water bowls to create a barrier that prevented ants from crawling onto it and consuming dead mosquito samples. During mosquito collection, a volunteer sits with their lower limbs placed inside the square trapping box (Fig. 2c) to act as attractive bait. Mosquitoes were captured by a single adult male per location using a MET over a 12-h period on each night of experiments (18:00–06:00 h). Sampling was conducted for 45 min of each hour, followed by a 15-min break period during which the trap was turned off, and mosquitoes collected either from the floor of the platform where they had fallen after electrocution, or from the grid panel surfaces using forceps. This 15-min break also allowed for exchange of collectors between matched indoor and outdoor stations at each house after each hour.Fig. 2

Step-wise setting and improvement made to the mosquito electrocuting trap (MET). a Locking together of hinges connecting individual panels with bolts; b locking of assembled panels into the main, outer frame; c fully assembled MET in use by a human participant wearing protective clothes except for on his feet, which are placed within the MET frame

This is a report on a small series of cases with hypoplastic thumb (Fig. 1) treated with a metatarsophalangeal transfer. We hereby certify that all applicable institutional and governmental regulations concerning the ethical use of human volunteers were followed during this research. Ethics committee of the Arak University of the medical Science approved the design of the study (IR.ARAKMU.REC.1400.230). Informed written consent was obtained from all participants.Fig. 1

Hypoplastic thumb: an underdeveloped, floating, nonfunctioning thumb with no bony or muscular support, attached to the hand by only skin and soft tissue

A fully balanced cross-over dose–response experiment was conducted using two I-LACT chambers of the SFS, one for the treatment and one for the control, whereby mosquitoes could interact with the human volunteers (Fig. 2). As previous experiments did not show any difference in the numbers of mosquitoes collected between the chambers, the treated and untreated emanators were fixed to the respective chambers for the duration of the experiment to avoid any potential contamination. Each experimental day, one replicate for biting and one for landing was conducted with the same volunteers. A replicate comprised 1 h of exposure to either the treatment (transfluthrin) or the negative control. To simulate an outdoor peridomestic setting, biting or landing was conducted 2 m from the end inside the I-LACT (Fig. 3). Four doses of transfluthrin-treated emanators (5 g, 10 g, 15 g and 20 g) were evaluated consecutively. Each dose was tested for six replicates, after which the emanator with the next highest concentration of transfluthrin was used.Fig. 2

Flow chart showing the various iterations of the experiments conducted in this study

Fig. 3

Schematic representation of the I-LACT used for the experiments. a Setup of the experiment with transfluthrin-impregnated eave-positioned targeted insecticide (EPTI) strips against Anopheles mosquitoes. b Setup of the experiment with freestanding transfluthrin passive emanators (FTPE) against Aedes aegypti

Two male volunteers aged 25–40 years were recruited by written informed consent. The volunteers were non-smokers and non-alcohol drinkers, and did not use perfumed cosmetics prior to the experiment to minimize heterogeneity in their attraction to mosquitoes [29 (link)]. To standardize the area available to the mosquitoes for biting (knees and ankles), the volunteers wore closed shoes and a bug jacket (Fig. 3). The volunteers were rotated between compartments (treatments) after each experimental day (one day for landing and the following day for biting) to account for differential attractiveness to mosquitoes between individuals [30 (link)]. Temperature and humidity were recorded inside one of the I-LACT using a Tiny Tag Gemini Data Logger (Chichester, West Sussex, UK). To ensure transfluthrin vaporization, the experiments were conducted at temperatures above 23 ºC [31 (link)].
On each experimental day, the treatment and control were allocated to one of the two chambers of the I-LACT 45 min before the experiment commenced, to allow emanation of the transfluthrin to have started before the experiment began. The experiment started when the volunteer sat down on the chair and the mosquitoes were released into the chamber of the I-LACT from the release cages, which were opened by pulling a string (Fig. 3).