Semi-field set up
The study was carried out in Western Kenya at the Centre for Global
Health Research, Kenya Medical Research Institute, Kisumu. The release
and recapture studies were conducted in a MalariaSphere a closed system
20m long x 8m wide(Knols et al. ,
2002)with slanted roofing (3m in the sides and 4.5m in the middle). The
entire structure is covered with insect-proof netting screen that
prevents mosquitoes inside the system from escaping into the
environment, or vice versa (Fig. 1 A). The system is also double doored
for the same reason. Inside the systema3m x 3m mud-walled hut is erected
resembling a typical house in the study village in terms of size,
structure and mosquito exit/entry points (eaves, window,and door) (Fig.
1B). The structure has local vegetation and grass floor to mimic the
natural vegetation and provide shelter for mosquitoes in the outdoor
environment (Fig. 1B). Two round clay pots are installed in the
enclosure but outside the hut to act as outdoor resting sites (Fig
1F).Inside the hut either a treated LLIN inside a bed-net trap (Mbita
trap)or an untreated net inside a bed-net trap as control was hanged
(Mathenge et al. , 2002). Treated
and untreated nets were used at different nights in the same hut. For
each night, a consented and remunerated human volunteer slept under the
bed-net trap in the hut. To offset any personal bias due to differential
sleeping habits or relative attractiveness to mosquitoes, two sleepers
were recruited for this experiment and took turns to sleep under the bed
net. They were instructed not to consume alcohol or smoke and avoid
deodorants during the study period. The volunteer who slept under the
bed net served as a bait to attract the mosquitoes into the hut but was
not bitten because of the net shield.