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Permethrin-impregnated curtains against phlebotomine sandflies (Diptera: Psychodidae): laboratory and field studies.

Maroli M, Majori G.

Department of Parasitology, Istituto Superiore di Sanita, Rome, Italy.

The efficacy of permethrin-impregnated nets against vectors of leishmaniases was evaluated in laboratory and field studies. Permethrin-impregnated curtains were tested at different dosages in experimental tunnel against Phlebotomus perniciosus and P. papatasi. The influence on feeding behaviour and the mortality rate post contact with the impregnated curtain were investigated. The vapour effect of permethrin on P. perniciosus adults confined less than 1 cm away from a treated net was also evaluated. From laboratory studies it seems that permethrin shows low or any barrier effect against sandfly species tested, and that the high insecticidal activity (mortality rate greater than 90%, 24 hours after the contact with treated net, 1 g/m2) and the reduction of biting rate observed (between 53.56% and 85.24%) are the main effects that make permethrin-impregnated nets very effective for sandfly control. In field studies carried out in cutaneous leishmaniasis foci of Italy, it was demonstrated that permethrin-impregnated curtains around windows and around CDC light traps, reduce the number of sandflies entering the stables and traps. In Burkina Faso, indoor use of wide-mesh cotton curtains impregnated with permethrin 1 g/m2 almost completely eliminate the occurrence of endophilic sandfly species. In conclusion the use of permethrin-impregnated curtains could be an alternative to residual house-spraying for the control of endophilic vectors of leishmaniases.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=1841235&dopt=Abstract permethrin Elimite



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Comparative effects of permethrin-impregnated bednets and DDT house spraying on survival rates and oviposition interval of Anopheles farauti No. 1 (Diptera:Culicidae) in Solomon Islands.

Hii JL, Birley MH, Kanai L, Foligeli A, Wagner J.

Department of Public Health and Tropical Medicine, James Cook University, Townsville, Qld, Australia.

Human-biting, CDC light trap and pig-baited collections were used to monitor changes in the abundance and parity rate of Anopheles farauti No. 1 mosquitoes in three Solomon Islands villages for 30 consecutive nights. Houses in one of the villages were sprayed with DDT, another village was unsprayed but its inhabitants used permethrin-treated bednets and the third village was left completely untreated. Mosquitoes collected each day were dissected to determine follicular maturation and parity. In the second year of vector control, survival rates (determined by time-series analysis of the landing catches and biting parous population) were significantly lower in the village using permethrin-treated bednets than in the other two villages. There was no difference in the estimated survival rates between the untreated and DDT-sprayed villages. The oviposition cycle was extended to 4 days in the permethrin-treated village compared with 3 days in the other villages. The expected infective life was 1.75-fold longer in the untreated village than in the permethrin-treated village. The epidemiological implications of replacing DDT spraying with permethrin for malaria control are discussed.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7495366&dopt=Abstract permethrin Elimite



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Induction of micronuclei by five pyrethroid insecticides in whole-blood and isolated human lymphocyte cultures.

Surralles J, Xamena N, Creus A, Catalan J, Norppa H, Marcos R.

Departament de Genetica i de Microbiologia, Universitat Autonoma de Barcelona, Bellaterra (Cerdanyola del Valles), Spain.

Five pyrethroid insecticides: cypermethrin, deltamethrin, fenpropathrin, fenvalerate and permethrin, were tested for their ability to induce micronuclei in both whole-blood (WB; three donors) and isolated human lymphocyte (IL, 2 donors) cultures, by using the cytokinesis-block method with 6 micrograms/ml cytochalasin B (Cyt-B). Fenvalerate and permethrin were tested with two different concentrations of Cyt-B (3 and 6 micrograms/ml). At the concentration ranges tested, all the five pyrethroids induced clear dose dependent cytotoxic effects, fenpropathrin being the most toxic. Nuclear division index (NDI) and the newly introduced index of cytotoxicity, the cytokinesis block proliferation index (CBPI), reflected the dose dependency more accurately than the percentage of binucleated cells did. CBPI is similar to NDI except that it estimates the average number of cell divisions that the cell population has gone through, and, therefore, classifies both trinucleate and tetranucleate cells into the same category. Cypermethrin and fenpropathrin slightly increased the number of MN and micronucleated cells in WB lymphocyte cultures from two out of the three donors. Deltamethrin produced a positive response only in WB cultures of one donor and in IL cultures of another donor. Permethrin gave mostly negative results, although it increased the MN frequency in WB cultures of one donor when 6 micrograms/ml Cyt-B was used. Fenvalerate did not significantly induce MN. With certain reservations to the purity and isomer composition of each pesticide, the existing information appears to support the idea that pyrethroid insecticides have a weak (cypermethrin, deltamethrin and fenpropathrin) or nule (fenvalerate and permethrin) genotoxic activity in vitro.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7529358&dopt=Abstract permethrin Elimite



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Village trial of bednets impregnated with wash-resistant permethrin compared with other pyrethroid formulations.

Miller JE, Lindsay SW, Armstrong Schellenberg JR, Adiamah J, Jawara M, Curtis CF.

Department of Medical Parasitology, London School of Hygiene and Tropical Medicine, U.K.

A village-scale field trial of pyrethroid-impregnated mosquito nets was undertaken in The Gambia, West Africa, in the Mandinka village of Saruja (13 degrees 13'N, 14 degrees 55'W) during July-November 1989. Nearly all the villagers possessed and used their own bednets. Anopheles gambiae is the main vector of human malaria in the area. An experimental wash-resistant formulation of permethrin was compared with standard emulsifiable concentrate (EC) formulations of permethrin and lambda-cyhalothrin, versus placebo-treated bednets. Target concentrations of pyrethroids on bednets were permethrin 500 mg/m2 and lambda-cyhalothrin 25 mg/m2. The experimental design involved random allocation of a treatment to one net per family. Whereas 68% of people questioned said they washed their nets fortnightly, observations during the 16-week trial period showed that only 4/130 (3%) of nets involved in the trial had been washed as frequently as once per month. Early morning searches for mosquitoes under bednets (1 day/week for 16 weeks) found significantly more mosquitoes (60% An.gambiae) in placebo-treated nets than in pyrethroid-treated nets. The numbers found with each of the three pyrethroid treatments did not differ significantly from each other. Insecticidal efficacy of the treatments was tested by bioassays using wild-caught unfed mosquitoes exposed to netting for 3 min. Linear regression analysis of bioassay mortality against number of times that a net had been washed by villagers showed that nets impregnated with the wash-resistant permethrin retained their insecticidal properties better than nets impregnated with lambda-cyhalothrin or with the standard permethrin formulation.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7696687&dopt=Abstract permethrin Elimite



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Comparative susceptibility of Periplaneta americana (L) to five pyrethroid insecticides.

Vythilingam I, Sutivigit Y.

Entomology Division, Institute for Medical Research, Kuala Lumpur, Malaysia.

Five pyrethroids namely, lambda-cyhalothrin, permethrin, deltamethrin, cyfluthrin and alpha-cypermethrin were evaluated using adult male and female cockroaches, Periplaneta americana (L). The American cockroaches were exposed for 10 minutes to glass jars treated with different concentrations of the five pyrethroids. The cockroaches were susceptible to all five pyrethroids and the susceptibility based on LC50 and LC50 were observed to be in the following order: lambda-cyhalothrin > permethrin > deltamethrin > cyfluthrin > alpha-cypermethrin The results showed that lambda-cyhalothrin was the most effective and alpha-cypermethrin was the least effective against Periplaneta americana (L).

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7777920&dopt=Abstract permethrin Elimite