A randomized and controlled comparison of the wash-resistances and insecticidal efficacies of four types of deltamethrin-treated nets, over a 6-month period of domestic use with washing every 2 weeks, in a rural area of Iran

ArticleinPathogens and Global Health 101(6):519-28 · October 2007with7 Reads
Impact Factor: 1.66 · DOI: 10.1179/136485907X193815 · Source: PubMed
Abstract

In a randomized, prospective, 6-month-long field study in a rural area of Iran, the wash resistances of 200 nets (40 PermaNet, 40 Yorkool and 40 A-Z nets), that their manufacturers claimed be long-lasting insecticidal nets (LLIN), were compared with those of 40 nets conventionally treated with deltamethrin (using K-O Tab tablets). All the nets were kept in routine domestic use and subjected to standardized hand-washing at 2-week intervals. Wild-caught or laboratory-reared Anopheles stephensi were used for the bio-assays of insecticidal activity. The regular washing and domestic use led to reductions in the insecticidal activities of all the treated nets after 6 months. Although the PermaNet nets showed the smallest reduction, they were not significantly better than the conventionally treated nets, which still showed acceptable insecticidal activity after 6 months. The PermaNet and A-Z nets both performed significantly better than the Yorkool nets, which were slightly but not significantly worse than the conventionally treated nets. In questionnaire-based interviews, the local householders were found to wash their own (non-study) nets at median and mean frequencies of every 2 and 2.1 weeks, respectively. In conclusion, the PermaNet nets showed better wash resistance than any of the other commercial nets, and were the only commercial nets tested that truly appeared to be LLIN. There still appears to be scope, however, for the impregnation, and thus the wash-resistance, of even the PermaNet nets to be improved.

    • "Tel.: + 86 571 8697 1923; Fax: + 86 571 8697 1923; E-mail: jinhaozhao@zju.edu.cn mammalian toxicity (Zaim et al., 2000; World Health Organization, 2001; Müller et al., 2002; Kayedi et al., 2007). However, laboratory studies indicate that fabrics impregnated with pyrethroids do not prevent vector mosquitoes from landing and therefore mosquito vectors may obtain a bloodmeal through wide-meshed nets or holed fabrics before knock-down (Cooperband & Allan, 2009). "
    [Show abstract] [Hide abstract] ABSTRACT: A new approach employing a combination of pyrethroid and repellent is proposed to improve the protective efficacy of conventional pyrethroid-treated fabrics against mosquito vectors. In this context, the insecticidal and repellent efficacies of commonly used pyrethroids and repellents were evaluated by cone tests and arm-in-cage tests against Stegomyia albopicta (=Aedes albopictus) (Diptera: Culicidae). At concentrations of LD50 (estimated for pyrethroid) or ED50 (estimated for repellent), respectively, the knock-down effects of the pyrethroids or repellents were further compared. The results obtained indicated that deltamethrin and DEET were relatively more effective and thus these were selected for further study. Synergistic interaction was observed between deltamethrin and DEET at the ratios of 5 : 1, 2 : 1, 1 : 1 and 1 : 2 (but not 1 : 5). An optimal mixing ratio of 7 : 5 was then microencapsulated and adhered to fabrics using a fixing agent. Fabrics impregnated by microencapsulated mixtures gained extended washing durability compared with those treated with a conventional dipping method. Results indicated that this approach represents a promising method for the future impregnation of bednet, curtain and combat uniform materials. © 2014 The Royal Entomological Society.
    Preview · Article · Nov 2014 · Medical and Veterinary Entomology
    T-T Yao T-T Yao L-K Wang L-K Wang J-L Cheng J-L Cheng +2 more authors... Y-Z Hu Y-Z Hu
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    • "Two types of treated bednets are in use for personal protection , the conventionally insecticide-treated bednets (CTNs) and long-lasting insecticide-treated nets (LLINs). The conventionally treated nets using pyrethroid insecticides have been tested in laboratory conditions (Graham et al. 2005; Sharma et al. 2005; Yates et al. 2005 ), in field conditions, in experimental huts (Asidi et al. 2005; Graham et al. 2005; Kayedi et al. 2007b; Malima et al. 2008), and at the community level (Alonso et al. 1993; Binka et al. 1996; Lengeler 2004; Nevill et al. 1996). Unfortunately, at that community level, most of the conventional bednets are still untreated mainly due to insecticide unavailability and to the distance between houses and treatment sites (Okrah et al. 2002). "
    [Show abstract] [Hide abstract] ABSTRACT: Insecticide-treated bednets play a cornerstone role in the efforts to control malaria. Bednets entomological efficacy is the determinant factor of their use to control malaria. In this study, we compared under laboratory conditions, the efficacy of two long-lasting nets (PermaNet® versus Interceptor®) and two treatments kits K-O TAB® (deltamethrin) versus Fendona 6SC® (alpha-cypermethrin) against Anopheles gambiae s.l. malaria vectors. The efficacy of washed and unwashed bednets was assessed by contact bioassays using World Health Organization (WHO) cones. Three to five-days-old mosquitoes were exposed to the netting for 3 min; the median and 95 % knockdown time, the after 24 h mortality was recorded for each type of bednet. The mortality after 24 h was equivalent for the Fendona 6SC® treated bednets and the K-O TAB® treated bednets [79.4 % confidence limits (CL) (73.9-84.6) and 74 % CL (68.3-80.0), respectively]. However, the Fendona 6SC® treated bednets were superior in 50 % knockdown time to the K-O TAB® treated bednets [7.8 min, CL (6.5-9.0) and 15. 2 min, CL (14.0-16.4), respectively]. Washed Interceptor® and PermaNet® bednets showed similar efficacy in terms of 50 % knockdown times. Mortality after 24 h was similar from the fifth to the twentieth wash, but PermaNet® performed better than Interceptor® for the first four washes and for unwashed bednets. This study showed that Fendona 6SC® kit and the Interceptor® bednets have exhibited consistent comparable efficacy in the laboratory compared to the well known and in use K-O TAB® kit and PermaNet® bednets.
    Full-text · Article · Jan 2014 · Parasitology Research
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    • "With the decrease of α long-lasting alpha-cypermethrin treated residue due to repeated washing, the entry index increased. The are several reports on the bioefficacy of bednet worldwide (Gimnig 2005, Kayedi et al. 2007, 2009, Gunasekaran and Vaidyanathan 2008, Oxborough et al. 2009). "
    [Show abstract] [Hide abstract] ABSTRACT: The Long-lasing insecticide impregnated nets (LLINs) is considered as an effective tools for malaria vector control. The aim of this study was to evaluate the residual efficacy of alpha-cypermethrin long lasting impregnated nets (LLIN-Interceptor(®)) against Anopheles stephensi using tunnel test. The wash-resistance of Interceptor(®) nets were assessed under laboratory conditions using tunnel test. Females of An. stephensi were released into the tunnel and then they were provided blood meals from guinea pigs. Bed nets were washed according to the standard procedure up to 20 times. The bioefficacy indicators such as inhibition of bloodmeal from experimental animal, knockdown, irritancy rate, survival rate, entry index and mortality were calculated. It induced 90-100% mortalities in the population of An. stephensi up to 15 washes. The KT50 values reduced from 73.47 to 26.30 minutes in unwashed in comparison to one washed, respectively. The mean of mortality rate of blood-feeding inhibition and entry indexes was reached to 91.6%±2.8, 87.0±3.4 and 24.9±2.8 respectively after 20 washing. This net could provide a good personal protection against malaria vectors and could induce relatively high mortality, inhibit the blood-feeding as well as reduce the entry rates of female mosquitoes even after several washes.
    Full-text · Article · Apr 2013 · Journal of Arthropod-Borne Diseases
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