Laboratory and experimental hut evaluation of a long-lasting insecticide treated blanket for protection against mosquitoes
Department of Entomology and Parasitology, Kilimanjaro Christian Medical University College (KCMUCo), Moshi, Tanzania; Pan-African Malaria Vector Research Consortium, (PAMVERC), Moshi, Tanzania; Department of Disease Control, London School of Hygiene and Tropical Medicine (LSHTM), London, United Kingdom; Africa University Development Office, Nashville, TN 37203-0007, United States; RTI International, Global Health Division, Nairobi, Kenya
Background: Long-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. Methods. Initial 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. Results: Cone 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. Conclusions: This 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. © 2014 Kitau et al.; licensee BioMed Central Ltd.
permethrin; pyrethroid; insecticide; pyrethroid; Anopheles arabiensis; Anopheles gambiae; antibiotic sensitivity; article; bed net; bioassay; blood; controlled study; Culex quinquefasciatus; enzyme linked immunosorbent assay; female; human; human experiment; insect control; insecticide resistance; laboratory test; long lasting insecticide treated blanket; mortality; mosquito; mosquito bite; nonhuman; normal human; protective equipment; Tanzania; textile washing; tropical medicine; wild species; animal; Anopheles; bed; Culex; drug effects; mosquito; procedures; time; Animals; Anopheles; Bedding and Linens; Culex; Humans; Insecticide Resistance; Insecticide-Treated Bednets; Insecticides; Mosquito Control; Pyrethrins; Time Factors