title: Long-term insecticidal activity and physical integrity of Olyset nets in Tafea Province, Vanuatu.
abstract: The long-term efficacy of long-lasting insecticidal nets (LLINs) depends on both the physical condition of the net and the residual activity of the insecticide. This study focused on monitoring these parameters in Olyset nets (Sumitomo Chemical Co., Osaka, Japan) (n = 101) that had been used for 1-3 yr in Tafea Province, Vanuatu. Net usage and frequency of washing was ascertained by questionnaire; the nets were assessed with regards to cleanliness and damage owing to holes. Insecticide efficacy was determined with cone bioassays using Anophelesfarauti Laveran. Net usage was high and 86.1% (87 of 101) of villages stated that they used the net every night. Washing of nets was low (11.9%, 12 of 101), and most nets (79.2%, 80 of 101) were considered dirty. Most nets were damaged (73.4% had holes), and 22.8% (23 of 101) had large holes (>200 cm2). The 24-h mortality of An. farauti exposed to nets aged 1-2 yr was 79.4%, while the mortality for nets 3 yr of age was significantly lower at 73.7%. There was no difference in the insecticidal activity of clean compared with dirty nets (mean 24-h mortality: Clean = 76.7%, Dirty = 77.1%). Although the majority of nets had holes, the physical condition of 8.9-22.8% of nets was altered so severely to potentially affect efficacy. Although the 3-yr-old nets would still be providing significant levels of insecticidal and personal protection, consideration should be given to replacing nets >3 yr old.
authors.affiliation: School of Population Health, Australian Centre for Tropical and International Health, Pacific Malaria Initiative Support Centre, University of Queensland, Public Health Building, Herston Road, Herston, Queensland 4006, Australia. shurajitdutta@gmail.com
authors.forename: Shurajit N
authors.initials: SN
authors.lastname: Dutta
authors.affiliation: National Vector Borne Disease Control Programme, Ministry of Health, Tafea Province, Vanuatu. Australian Army Malaria Institute, Gallipoli Barracks, Enoggera, Queensland 4052, Australia.
authors.forename: James
authors.initials: J
authors.lastname: Amon
authors.affiliation: National Vector Borne Disease Control Programme, Ministry of Health, Tafea Province, Vanuatu. Australian Army Malaria Institute, Gallipoli Barracks, Enoggera, Queensland 4052, Australia.
authors.forename: Harry
authors.initials: H
authors.lastname: Iata
authors.affiliation: James Cook University, Faculty of Medicine, Health and Molecular Sciences, Queensland Tropical Health Alliance, MacGregor Rd, Cairns, Queensland 4870, Australia.
authors.forename: Robert D
authors.initials: RD
authors.lastname: Cooper
authors.affiliation: School of Population Health, Australian Centre for Tropical and International Health, Pacific Malaria Initiative Support Centre, University of Queensland, Public Health Building, Herston Road, Herston, Queensland 4006, Australia.
authors.forename: Tanya L
authors.initials: TL
authors.lastname: Russell
mesh_terms: D000818:Animals; D000852:Anopheles; D006801:Humans; D007306:Insecticides / Q000032:analysis*; D008288:Malaria / Q000517:prevention & control; D057147:Mosquito Nets / Q000592:standards*; D010573:Pesticide Residues / Q000032:analysis*
chemical_list: D007306:Insecticides; D010573:Pesticide Residues