Laboratory and experimental hut evaluation of a long-lasting insecticide treated blanket for protection against mosquitoes

Abstract

BackgroundLong-lasting insecticide treated blankets (LLIBs) may provide additional protection against malaria where use of long lasting insecticidal nets (LLIN) is low or impractical such as in disaster or emergency situations.MethodsInitial efficacy testing of a new candidate LLIB was carried out at LSHTM and KCMUCo, before and after washing, in cone and ball bioassays and arm-in-cage tests against pyrethroid susceptible Anopheles gambiae. A small scale field trial was conducted using veranda-trap experimental huts in northern Tanzania against wild An. arabiensis and Culex quinquefasciatus mosquitoes. Treatments included unwashed and 5 times washed permethrin treated LLIB and blankets hand-treated with permethrin (ITB), untreated blankets, and a holed unwashed Olyset net.ResultsCone test mortality was 75% for LLIB when unwashed, but decreased to 32% after 5 washes and <10% after 10 washes. In arm-in-cage tests protection against biting was 100% for LLIBs regardless of the number of washes while reduction in landings was 79% when unwashed, 75% after 5 washes, but declined to 41% after 10 and 33% after 20 washes. In ball bioassays using pyrethroid resistant An. arabiensis, mortality was low in all treatments (<35%) and there was no significant difference in mortality between Olyset net, LLIB or ITB (p > 0.05). Percentage mortality of An. arabiensis in huts with LLIB unwashed (26%) was not statistically different to Olyset net (31%, p = 0.5). The 5 times washed LLIB reduced blood-feeding by 49% which was equivalent to Olyset net (p > 0.086). There was no significant difference in percentage blood-feeding between LLIB and ITB unwashed or 5 times washed (p = 0.147 and p = 0.346 respectively). The 5 times washed LLIB reduced blood-feeding of Culex quinquefasciatus by 40%, although the Olyset provided the greatest protection with 85% inhibition. ELISA analysis of a sub-sample of blood fed mosquitoes showed that not all had fed on humans in the huts, therefore blood-feeding inhibition may have been underestimated.ConclusionsThis trial demonstrated the potential of LLIBs to provide substantial personal protection even against pyrethroid resistant mosquitoes. LLIBs may prove particularly useful where LLINs are unsuitable or net usage is low.

The behaviour of mosquitoes in relation to humans under holed bednets: the evidence from experimental huts

“…As shown in studies with different sizes or numbers of holes, or in studies with and without holes, the general and unsurprising, observation is that with increased holes there is increased blood feeding by mosquitoes in experimental huts. Before continuing, it should be noted that the presence of blood-fed mosquitoes in an experimental hut do not mean that the mosquitoes have fed on the person inside the hut ( Kitau et al 2014 ).There are several factors that influence a mosquito’s ability to feed on a human protected by a net, including the presence of holes in the net, the resistance of the mosquito to the insecticide on the net and the proximity of the human to the net (determined by the size of the net, the number of people inside the net, the sleeping location of the human, etc. ), which could allow feeding through the net.…”

Assessment of mosquito larval productivity among different land use types for targeted malaria vector control in the western Kenya highlands

“…These highland sites have also received wide coverage of indoor residual spray (IRS) [ 22 ]. While these strategies may be effective in adult vector control, more emphasis should be placed on controlling the aquatic stages, particularly since the protection offered by current tools in adult vector control has been compromised by intensified insecticide resistance within malaria vector populations [ 23 , 24 ]. Targeting immature stages and developing monitoring information systems is of paramount importance in effective larval control.…”

Effects of a new outdoor mosquito control device, the mosquito landing box, on densities and survival of the malaria vector, Anopheles arabiensis, inside controlled semi-field settings

“…Fortunately, there are some definitions of what the target products should look like to effectively protect humans against malaria vectors while outdoors [ 18 ]. Amongst the candidate products that have been proposed and tested are: (1) spatial repellents which have proven effective for practical community uses either in vapour or aerosol formats [ 19 – 21 ]; (2) topical repellents such as DEET [ 22 , 23 ]; (3) insecticidal treated clothing [ 24 , 25 ]; (4) insecticide treated cattle [ 26 , 27 ]; (5) larval source management [ 28 , 29 ]; and, (6) toxic sugar baits [ 30 , 31 ].…”