Effectiveness of Soap Formulations Containing
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J. Avr. Mosq. CoNrnol Assoc 63 EFFECTIVENESSOF SOAPFORMULATIONS CONTAINING DEET AND PERMETHRIN AS PERSONALPROTECTION AGAINST OUTDOOR MOSQUITOESIN MALAYSIA H. H. VAP School of Biological Sciences,Universiti Sains Malaysia, Penang, Malaysia ABSTRACT. Two soap formulations, both containing20To deet and one each containing permethrin at 0.5 and l.0Vo, respectively, were applied to exposed arms and legs of volunteers as personal protection against outdoor human biting mosquitoes in six locations on Penang Island, Malaysia. The predominant mosquito species collected from these locations were Aedesalbopictus, Mansonia uniformis, Culex geli.dus,Anopheles lesteri, and Armigeressubalbatus. Efficacy and residual effects up to 4 hours indicated good protection against these species. Reduction in mosquito landing-biting rates in treated groups ranged from 83.8 to 100.0%. At high densities, small percentages of Ma. unifurmis and An. lesteri landed or bit on treated skin. Use of the soap formulations in terms ofcost-effectiveness, safety and overall vector control strategy for some tropical diseasesis discussed. INTRODUCTION daily temperature of 27"C and a relative humidity of 60-80% year round. The central Since the late 1970s, research in the devel- part of the island is hilly with elevations of opment of personal protection measures around 450 m. The hills are covered with sec- against mosquitoes and other biting arthropods ondary rain forests surrounded by lowlands, prevalent. perme- has been Field studies with coastal plains and sandy beaches. thrin impregnated clothing have been shown to Six rural locations on Penang Island, reflect- be effective against mosquitoes, ticks, chigger ing different ecological habitats with different mites, phlebotomine flies, black flies and other predominant mosquito species, were chosen to (Breeden biting flies et al. 1982, Lindsay and test the efficacy of the soap formulations. McAndless 1978, Schreck et al. 1977, 1978a, Trees, shrubs and grasses are ubiquitous with 1978b, 1980, 1982). Permethrin has also been human habitations dotting the landscapes in topically applied in dust formulations for these locations. The test locations were situated human (Nassif body louse control and Kamel in the lowland areas at or near the coastal plain. 1977, Nasif et al. 1980). The locations were as follows: (l) Universiti More permethrin-impregnated recently, Sains Malaysia, Minden Campus of about 400 provide mosquito nets have been shown to bet- hectares with well-maintained buildings and ter protection than untreated nets against surroundings; (2) Permatang Damar Laut, a Anopheles mosquitoes (Darriet et al. 1984). rural village at the southeast corner of the is- Moreover, permethrin when was applied to land, an area covered with double or single clothing and deet was applied to exposed skin, storey wooded houses scattered over a wide the provided combination a high degree of area, and the houses are without clear-cut com- protection against the bites of Aedes taeniorhyn- pounds, many types of trees and shrubs are (Schreck chus Wiedemann et al. 1984). found in and around the houses; (3) Gertak Pressurized sprays of permethrin and deet on Sanggul, a fishing village on the sourhwest clothing have also proven to be highly effective shore of the island; (4) Sungai Rusa, Balik against some species (Mount tick and Snoddy Pulau District, a rice farming village ar rhe 1983). midwestern part of the island about 5 km from The present studies were carried out to de- the coastline; (5) Permatang Pasir, Balik Pulau termine the effectiveness of a soap formulation District, a rubber plantation estate ad,jacent to containing deet permethrin and against mos- Sungai Rusa; and (6) University:s Mukahead quitoes in a few selected locations Penang on Biological Station, at the northwest tip of the Island, Malaysia. These test sites provided a island and located on the coastline surrounded spectrum of common mosquito species in by secondary forests. Malaysia. Two formulations of soaps containing per- methrin (cis:trans ratiol. 25:75) and deet were provided by Mr. MATERIALS AND METHODS Tom Simmons. The content of deet in the two soap formulations was 207o, The studies were carried out on Penang Is- whereas, permethrin was present at dosage of land, Malaysia with an approximate land area 0.5 and 1.0% for formulation A and B, respec- of 320 km2 and is situated at the northwest coast tively. of the Malay Peninsula facing the Strait of Subjects wearing a T-shirt and long rrousers Malacca and the Bay of Bengal. The weather of exposed their untreated arms and legs to assess the island is essentially tropical with an average the density of biting/landing mosquitoes. Using 64 J. Ar.,r.Mosq. CoNrnol Assoc. Vor-.2,No. I small specimen tubes, each subject collected all At test location Permatang Damur Laut, four mosquitoes landing or biting on the exposed untreated subjects were tested against four skin within a specific time. Depending on the subjects with blank soap application (soap with- density of the mosquitoes, each collecting pe- out deet and permethrin) to ascertain the effect riod ranged from 20 to 60 minutes. of the blank soap on mosquito landing-biting At each test location, 12 human subjects were rates. employed. Four subjects were untreated checks, All the mosquitoes collected were identified four subjects were treated with soap formula- with assistance from the staff of the Medical tion A and four with formulation B. The ex- Entomology Division, Institute for Medical Re- posed arms and legs of untreated subjects were search, Kuala Lumpur, Malaysia. wetted with tap water and allowed to dry natu- rally hrefore the initiation of mosquito collec- RESULTS AND DISCUSSION tions. For the treated subjects, the soap formu- lations were applied on prewetted arms and The overall mosquito landing/biting rate per legs and a uniform film of lather was achieved man-hour and the predominant mosquito spe- by rubbing the applied surfaces vigorously. The cies at each test location are shown in Table l. lather was allowed to dry naturally before the The mosquito densities per man-hour ranged initiation of the mosquito collections. At each from a high of 51.2 at Permatang Damar Laut test location, the subjects were seated at least 3 to a low of 4.5 at Gertak Sanggul and the pre- m apart in a linear arrangement around the dominant species at each test location varied. house compounds. The untreated control sub- The differences in densities and species com- jects were seated at both ends of the linear ar- positions reflected the different ecological rangement. A total of 4 hours was allotted to habitats of the test locations. Thirty-one species assess the efficacy and residual effect of the of mosquitoes were collected from the six test soap formulations at each test location. The locations, including 9 species of Aedes,5 species choice of the time schedules for each location of Anopheles,5 species of Armigeres,9 species of corresponds with the peak biting hours of the Culex and 3 speciesof Mansonia (H. H. Yap and crepuscular man-biting mosquitoes in Malaysia. coworkers, unpublished data). Permatang In order to tie in with the peak densitiesof cer- Damar Laut and Sungai Rusa had the highest tain mosquito species, some of the experiments diversity of species with l7 and l9 species, re- were carried out on two consecutive nights for 2 spectively. Of the total number of mosquitoes hours each night. To simulate the residual ef- collected, males constituted about 5%. fect of the soap formulation at the third and Among the predominant species (Table l), fourth hours after treatment. the formulations Aedesalbopicns (Skuse) is ubiquitous on Penang were applied 2 hours prior to the collection of Island, Malaysia. This finding confirms the re- the mosquitoes on the second night. Time sults of an earlier ovitrap survey conducted for schedules of the collections at each test location the whole of Penang Island (Yap 1975). Aed,es are shown in Table l. albopictus is a vector for dengue and dengue Table l. Time schedules, mosquito densities and predominant mosquito species collected by the untreated check subjects at each of the six test locations on Penang Island, Malaysia for the efficacy studies of soap formulations. Time schedules for testing and Overall mosquito collection of landing-biting rate Predominant mosquito mosquitoes per man-hour species collected (Va of Test locations (local time)" (Mean+S.E.) total collection) l. University's Minden Campus 1900-2100hr. 27.6*3.1 Ma unifurmis (53%) Ae. aLbopictus(26Vo) 2. Permatang Damar Laut l90G-2100hr. 51.2+4.7 Ma. uniformis (70o/o) Cx. fulcocephalus (l4Vo) 3. Gertak Sanggul 1600-2000hr. 4.5+1.6 Ae. alboprctus (88Va) 4. Sungai Rusa, 1900-2100hr. 29.3+4.4 Cx. gelidus (397a) Balik Pulau District An. lesteri (38Vo) 5. Permatang Pasir, 1600-2000hr. 10.8t 1.9 Ae. albopictus(79%) Balik Pulua District 6. Mukahead Biological Station 1600-2000hr. 6.9+1.6 Ar. subalbatus (58Vo) Ae. albopictus(217a) a For test locations with time schedules of 2-hour intervals, the experiments were repeated in two consecuttve nights to assessthe residual effects in a 4-hour period. .