8- Dr Akbarzadeh RTL Iranian J Arthropod-Borne Dis, 2010, 4(1): 60–65 A Raeisi et al.: Residual Effects of Deltamthrin … 60 Original Article Residual Effects of Deltamethrin WG 25% as a New Formulation on Different Surfaces against Anopheles stephensi, in Southeastern Iran A Raeisi 1 , MR Abai 2 , * K Akbarzadeh 2 , M Nateghpour 2 , M Sartipi 3 , A Hassanzehi 4 , N Shahbakhsh 4 , L Faraji 1 , F Nikpour 1 , M Mashayekhi 5 1 Malaria Control, Ministry of Health and Medical Education, Tehran, Iran, 2 Department of Medical Entomology and Vector Control, School of Public Health, Tehran University of Medical Sciences, Iran 3 Iranshahr Center of Public Health, Iranshahr, Iran 4 Zahedan University of Medical Sciences, Zahedan, Iran 5 Kerman University of Medical Sciences, Kerman, Iran (Received 9 Oct 2009; accepted 19 May 2010) Abstract Background: Indoor residual spraying (IRS) is functioned as national interventions against malaria in southeastern foci of Iran and deltamethrin WP one of the insecticides have been used since past decade. In this study, the residual activity of the wettable granule (WG) was studied on different surfaces in hut scale trial against Anopheles stephensi in Iranshahr District, southeastern Iran. Methods: Three dosages of 25, 40 and 50 mg a.i./m 2 of deltamethrin WG 25% formulation were applied on plaster, cement, mud, and wooden surfaces using Hudson ® X-pert compression sprayer having 10 litters capacity. Results: The residual effects of deltamethrin WG 25% on different surfaces was assessed based on reduction of mortality An. stepehnsi from 100% to about 70%. At 25, 40 and 50 mg a.i./m2 the WG formulation of deltamethrin had a bioefficacy for about 2, 3 and 4 months respectively. Conclusion: There was an expectable fluctuation in mortality of An. stephensi at different sprayed surfaces as well as dosages. The proposed 50 mg/m2 WG is the longest activity for up to 4 months which needs to be applied for two spraying cycles per year at the climatically condition of southwestern Iran. Keywords: Deltamethrin, Wettable granule (WG), Anopheles stephensi, Malaria, Iran Introduction Sistan and Baluchistan Province, in the Southeast of Iran is considered as the most prevalent area for malaria, which contains about 42–60% of the total malaria cases in Iran (Sadrizadeh 2001). Various factors cause refractory malaria in Sistan and Balu- chistan Province. Presence of five malaria vector including Anopheles culicifacies, An. stephensi, An. fluviatilis, An. superpictus, An. dthali, and An. pulcherrimus (as a sus- pected vector) has a major role in this sce- nario (Manouchehri et al. 1976). Knowing the best and effective way is very important in malaria elimination as a new strategy in Iran. Indoor Residual spraying (IRS) has been considered as the main attempts for control of malaria in Iran since 1950. Resis- tance to DDT, dieldrin and malathion have been developed on five out of seven malaria vectors in Iran (Mofidi et al. 1958, WHO 1970, Manouchehri et al. 1976). After ap- *Corresponding Author: Mr Kamran Akbarzadeh, Email: akbarzadehk@yahoo.com Iranian J Arthropod-Borne Dis, 2010, 4(1): 60–65 A Raeisi et al.: Residual Effects of Deltamthrin … 61 pearance of the resistance in An. stephensi, main malaria vector in southern Iran, the house spraying was continued with different adultricides e.g. propoxur from 1978 to 1993 for 13 successive years, Actellic ® and pro- poxur from 1991 to 1992 and from 1993 to 2000 both lambdacyhalothrin (Icon 10% WP) and propoxur have been used for ma- laria control in the south of Iran (Ladonni et al. 1995). At present, the IRS operation in Iran has been continued with deltamethrin WP 5% since 2003 but the residual activity of del- tamethrin 25% WG has not been studied at field condition of Sistan and Baluchistan Prov- ince, which is the endemic area for malaria as well as main area for application of the IRS in the country. The main objective of this study was to study the residual activity of deltamethrin WG 25% as a new formulation, on different sur- faces in human dwellings at malarious area, southeast of Iran. Materials and Methods The field operation was carried out in Malek- Abad Village, at suburbs of Iranshahr City from July to December 2006. The lab-bred Anopheles stephensi (IRS strain), sugar fed 2-3 days old females were used for bioassays. The adult were provided from insectary of Iranshahr Research Sta- tion, 25 km away from trial area. Tempera- ture and relative humidity of the insectary were 28±2° C and 65±5% respectively. Deltamethrin WG (Wettable Granule) with empirical formula C22H19Br2NO3 avail- able under trade name K-Othrine ® WG25, supplied by Bayer Environmental Sciences, Co. This insecticide were sprayed at 25, 40 and 50 mg/m 2 on different surfaces including plaster, wood, mud and cement using a Hud- son X-pert ® sprayer (10 liters capacity) with HSS-8002 nozzle which equipped with a re- gulator adjusted pressure at range 25–45 psi . The contact bioassay tests were carried out according the method recommended by World Health Organization, using conical cha- mber at biweekly interval (WHO 1975). A lot of 10–12 adult females were gently released in any cone at 9 replicates (upper, middle and lower parts of walls) using aspirator with 30 min exposure on treated surfaces as well as 3 replicates of untreated surfaces as negative controls simultaneously. At the end of expo- sure time, the adults were transferred into clean cup and maintained at optimal condition and the mortality was recorded after 24 h. If mor- tality rate of control tests was between 5–20%, the mortality rates were corrected using Ab- bott’s formula. The data (mortality rates) was transferred using arcsine formula. In order to compare the residual activities in each sprayed surfaces, one- way ANOVA, Levene’s test, HSD test, or Games-Howell test were used. The criteria for residual effect of tested insecticide were based on mortality rate and if this rate was decreased to 70%, the bioas- says stopped and the data analyzed. Results Comparisons of three applied dosages (25, 40 and 50 mg/m 2 ) showed an efficacy around 3, 3.5 and 5 months on plaster sur- faces respectively (Fig. 1). On mud surfaces, the residual activity of at 25, 40 and 50 mg/m 2 were estimated around 2.5, 3.5 and 4.5 months respectively (Fig. 2). Residual efficacy of experimental dos- ages of deltamethrin WG 25% at 25, 40 and 50 mg/m 2 on cement surfaces was around 1, 2 and 2 months respectively (Fig. 3). It is cleared that the average mortality rates of all three dosages did not exceed to 100% anytime. Iranian J Arthropod-Borne Dis, 2010, 4(1): 60–65 A Raeisi et al.: Residual Effects of Deltamthrin … 62 A wide enhancing ranges of efficacy of del- tamethrin WG 25% at applied dosages (25, 40 and 50 mg/m 2 ) was considered on wood surfaces around 2, 3.5 and 4.5 months re- spectively (Fig. 4). 0 20 40 60 80 100 120 5 20 35 50 65 80 95 110 125 140 155 170 Post-treatment days M o rt a li ty ( % ) 25 mg/m2 40 mg/m2 50 mg/m2 Deltamethrin 25% WG ; 25 , 40 & 50 mg/m 2 Residual spraying on Plaster ANOVA ( α=0.05) Fig. 1. Efficacy of various doses (25, 40 and 50 mg/m 2 ) of deltamethrin WG 25% on plaster surfaces, Malek-Abad Village, Iranshahr, southeastern Iran, 2006 0 20 40 60 80 100 120 5 20 35 50 65 80 95 110 125 140 155 170 Post-treatment days M o rt a li ty ( % ) 25 mg/m2 40 mg/m2 50 mg/m2 Deltamethrin 25% WG ; 25 , 40 & 50 mg/m 2 Residual spraying on Mud ANOVA ( α=0.05) Fig. 2. Efficacy of experimental dosages (25, 40 and 50 mg/m 2 ) of deltamethrin WG 25% on mud surfaces, Malek- Abad Village, Iranshahr, southeastern Iran, 2006 Iranian J Arthropod-Borne Dis, 2010, 4(1): 60–65 A Raeisi et al.: Residual Effects of Deltamthrin … 63 0 20 40 60 80 100 120 5 20 35 50 65 80 95 110 125 Post-treatment days M o rt a li ty ( % ) 25 mg/m2 40 mg/m2 50 mg/m2 Deltamethrin 25% WG ; 25 , 40 & 50 mg/m 2 Residual spraying on Cement ANOVA ( α=0.05) Fig. 3. Efficacy of experimental doses (25, 40 and 50 mg/m 2 ) of deltamethrin WG 25% on cement surfaces, Malek- Abad Village, Iranshahr, southeastern Iran, 2006 0 20 40 60 80 100 120 5 20 35 50 65 80 95 110 125 140 155 170 Post-treatment days M o rt a li ty ( % ) 25 mg/m2 40 mg/m2 50 mg/m2 Deltamethrin 25% WG ; 25 , 40 & 50 mg/m 2 Residual spraying on Wood ANOVA ( α=0.05) Fig. 4. Efficacy of experimental dosages (25, 40 and 50 mg/m2) of deltamethrin WG 25% on wood surfaces, Malek- Abad Village, Iranshahr, southeastern Iran, 2006 Iranian J Arthropod-Borne Dis, 2010, 4(1): 60–65 A Raeisi et al.: Residual Effects of Deltamthrin … 64 Discussion Determination of residual activity of insecticides is the essential information for the use of indoor spraying operation. The re- sidual duration of pyrethroids recommended by WHO including alphacypermethrin, bifenthrin, cyfluthrin, deltamethrin, etofen- prox, and lambdacyhalothrin WP, have esti- mated between two and six months (Najera et al. 2001). Study on residual efficacy of deltame- thrin 2.25% WG at 25 mg/m 2 against An. culicifacies in India showed 100% mortality up to 12, 10, 9 and 12 weeks on mud, ce- ment, brick and thatch surfaces respectively (Ansari et al. 1997). A village scale trial of deltamethrin 2.25% WG at 25 mg/m 2 against both anophelinae and culicinae mosquitoes also indicated a residual life about 12 weeks both on mud and cement plaster surfaces in India (Singh et al. 1989). In Brazil, residual activity of SC formulation of deltamethrin at 25 mg/m 2 reported 3, 2 and 3 months on wood, plastered brick and brick surfaces re- spectively (Santos et al. 2007). The extended field trial of deltamethrin 2.5% WP at 25 mg/m 2 confirmed the long residual effec- tiveness from 15 to 16 weeks on both mud and cement plastered surfaces in India (Gill et al. 1997). The residual activity of WG formulation of deltamethrin at 25 mg/m 2 was effective for 6 weeks after treatment on Aedes vectors in Kuala Lumpur, based on biweekly bioassay (Rozilawati et al. 2005). Based on the present study, 50 days old deposits of insecticide on plaster surfaces caused similar mortality with three dosages (25, 40 and 50 mg/m 2 ) of deltamethrin WG 25% (P<0.05). Significantly enhance mor- tality with increasing in dosages has seen on mud surfaces after 50 days. Surprisingly on mud surfaces there was no significant difference between three ap- plied dosages until day 110. Despite of early depredating of the insecticide on very absor- bent cement surfaces, there was no signifi- cantly difference between three applied dos- ages on cement surface. On wood surfaces, the residual effects of all three dosages did not show a significant difference with each other until day 50 as the same for 25 and 40 mg/m 2 until day 80. At greater age after 80 (days 90- 110) the variation between dosages 40 and 50 mg/m 2 was not significant but with dose 25 mg/m 2 the difference was significant (P<0.05). The persistency of insecticides, as re- vealed by mortality, depended on the type of surface, the dosage, and the age of spray de- posits (Giga et al. 1991). In comparison with the results presented by other authors, our study revealed a clearly lower estimation of resid- ual effect of deltamethrin WG 25% on vari- ous surfaces. It seems that the irritancy effect of deltamethrin on tested mosquito, An. ste- phensi IRS strain may responsible for this difference. In mosquitoes, it is commonly ob- served that casual contact with a surface treated with deltamethrin (or other pyrethroids) can produce an irritant effect, causing the insect to fly away-an effect known as excito-repel- lency (Dartigues 1987). Study of efficiency of pyrethroids at laboratory condition also showed similar effect related to type of pyrethroids (Alipour et al. 2006). Also other field bioas- says of deltamethrin WP %5 which conducted by authors revealed a clearly excito-repel- lency effect. In the present study, the excito- repellency phenomenon were not equally oc- curred in applied dosages. The excito-repel- lency effect of deltamethrin WP can be de- feated by using the WG formulation in Sis- tans and Baluchestan Province. In conclusion, field hot scale evaluation of deltamethrin WG can be recommended for finding the effects of the insecticide on po- pulation dynamic of vectors, effects of other materials and human behaviors on residual ef- fect of the insecticide. Iranian J Arthropod-Borne Dis, 2010, 4(1): 60–65 A Raeisi et al.: Residual Effects of Deltamthrin … 65 Acknowledgements The authors would like to thank the Malaria Control Office, Ministry of Health and Medical Education for financial support. The authors also like to thank Health Center of Sistan and Baluchestan Province for pro- viding the facilities to carry out the field tri- als. The authors would like to acknowledge with gratitude the assistance of staff of Iran- shahr Medical Research Station for their kind cooperation with this research. The authors declare that they have no conflicts of interest. 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