N,iV-diethylphenylacetainide in Treated Fabrics as a Repellent Against Aedes aegypti and Culex quinquefasciatus (Diptera: Culicidae) K. M. RAO, 1 SHRI PRAKASH,1 SANTOSH KUMAR,1 M.V.S. SURYANARAYANA,1 M. M. BHAGWAT, 2 M. M. GHARIA, 2 AND R. B. BHAVSAR2
J. Med. Entomol. 28(1): 142-146 (1991) ABSTRACT The efficacy of fabrics impregnated with N,2V-diethylphenylacetamide (DEPA), a new repellent, was studied in the laboratory and field against Aedes aegypti (L.) and Culex quinquefasciatus Say. DEPA-treated polyester cotton and cotton fabrics provided repellency for 30 and 36 d and had a half-life of 11 and 5 d, respectively. The repellent could not be applied at a rate of > 15% of fabric weight. DEPA-treated fabric patches were found to be a practical and novel approach and were effective for 90 d in the laboratory against Ae. aegypti and 77 d in the field against Cx. quinquefasciatus. Insecta, repellents, mosquitoes, N,N-diethylphenylacetamide
of insect repellents directly to the skin gives protection for only a few hours because it is lost by evaporation, abrasion, and absorption (Shorey & McKelvey 1977). Topical application of repellents may not be cosmetically acceptable in hot and humid climates, especially in the northeastern regions of India, which are heavily infested with hematophagous insects and land leeches. The application of insect repellents to textiles is an alternative that provides longerlasting protection against these organisms. Repellent- and insecticide-impregnated clothing and wide-mesh netting have been found to be effective against hematophagous insects (Gouck & Moussa 1969, Grothaus et al. 1972, Gupta et al. 1987, McGovern & Schreck 1988). However, application of the chemical on fabrics should not affect the aesthetic properties of the cloth. N,N-diethylphenylacetamide (DEPA), a nontoxic, nonirritant, cosmetically acceptable, indigenously available, cost-effective, broad-spectrum repellent, has been developed recently (Kumar et al. 1984; Kalyanasundaram et al. 1986; Prakash et al. 1987, 1988; Rao et al. 1987, 1988a,b). Based on these extensive bioemcacy and toxicology studies, the Drug Controller of India (Ministry of Health) has issued a license for the manufacture of DEPA for use on humans. Because repellent textiles are a practical approach for protection against hematophagous insects, we report here the repellency of DEPAimpregnated fabrics based on slow-release technology. The duration of effectiveness of DEPA was THE APPLICATION
1 Defence Research and Development Establishment, Gwalior474002, India. 2 Ahmedabad Textile Industry Research Association, Ahmedabad 380015, India.
compared with N,N-diethyl-m-toluemide (DEET), a widely used repellent. Materials and Methods Test Chemicals. Two insect repellents were used. N,N-diethylphenylacetamide was synthesized in the laboratory (Sharma et al. 1984). DEET was obtained from M/s Fluka, Chemie AG Industriestrasse CH-9470 Buchs, Switzerland. Treatment of Fabrics. Printing and padding techniques were used for impregnating polyester cotton (2:1) and cotton fabrics with the insect repellents. Attempts to apply the repellents to the exterior surface of the fabric were abandoned because the thickeners were not compatible with the repellents or required elevated curing temperatures (130-150°C) which evaporated the repellents. Impregnation of the fabric by padding was of interest because the insect repellent was distributed uniformly. The padding recipe contained 10% repellent, 30% film-forming binder based on an acrylic copolymer (aminoacridine, copolymer Stryrene n-butylacrylate and methylol) (M/s Colourchem, Bombay, India), 6% fixer (melamine formaldehyde trimethylamine, 50% solution), 3% emulsifier, and 1% glacial acetic acid (acid-liberating catalyst which cured the binder at room temperature without loss of repellent). Evaluation of Repellency Against Mosquitoes.
The repellent activities of DEPA and DEET were evaluated by inserting a human hand covered with gloves or detachable patches into a test chamber (75 by 60 by 60 cm). The treated 150-cm2 surface was exposed for 5 min in the test chamber containing 200 Ae. aegypti (L.) females. The numbers of insects landing and biting were counted independently by two observers. Untreated fabric sam-
0022-2585/91/0142-0146$02.00/0 © 1991 Entomological Society of America
Downloaded from http://jme.oxfordjournals.org/ by guest on December 19, 2015
KEY WORDS
January 1991
RAO ET AL.: IMPREGNATED FABRICS FOR MOSQUITO REPELLENCY
143
pies were used as controls. Fabrics receiving fewer than five bites in 5 min (threshold) were considered to exhibit repellency. Observations were made twice weekly; however, the data are presented as weekly or fortnightly means. After ascertaining the effects of DEPA-impregnated fabrics and detachable patches in the laboratory, field trials using garments having five 10% DEPA-treated detachable patches were performed; four pieces (15 by 15 cm) were attached on the front and one patch (30 by 6.25 cm) on the back (Fig. 1 A and B). The patches were affixed by press buttons. The trials were carried out in a sylvan habitat of Gwalior from 1700 to 2200 hours. Seven subjects (four replicates) were used in each trial. Human volunteers wearing these garments were seated 1 m apart. Unprotected subjects wearing the garments without patches were exposed during each test period; the biting rate averaged 30-40 Culex quinquefasciatus Say per man-hour. The duration of effectiveness was determined at fortnightly intervals as percentage protection by comparing subjects with uniforms with and without patches. The trials were abandoned after protection from the patches decreased to 15% of the weight of the fabric because this concentration adversely affected the feel as well as the desirable properties of the cloth. Repellent-impregnated fabrics were found to lose their efficacy rapidly after washing with soap detergent in water. The concentration of repellent on day 5 after one washing was found to be 0.5% of the weight of the fabric; 20 bites of Ae. aegypti were recorded in a bioassay. Detachable Patches. DEPA-treated detachable patches were evaluated in the laboratory against Ae. aegypti and in the field against Cx. quinquefasciatus. Patches were effective for 90 d against Ae. aegypti in the laboratory. The data were statistically significant (F = 16.38; LSD, 2.59; P < 0.01) (Table 2). In the field, the treated patches offered 96% protection on day 1 against Cx. quinquefasciatus. However, the effectiveness of these patches decreased to 67% by day 77. The number of bites per hour on control volunteers was always statistically greater than on the volunteers who wore impregnated patches (F = 103.2; LSD, 4.4; P < 0.001) (Table 3). Discussion Two techniques were used for impregnating the fabrics. The padding method of impregnation was found to be superior because repellent and other ingredients were uniformly distributed and the loss of repellent during curing was minimal. McGovern & Schreck (1988) evaluated the effects of monocarboxylic esters and aliphatic diols on cotton stockings against mosquitoes. Effectiveness was based on the time until five bites were received. The authors considered compounds that provided protection for 11 d as promising repel-
Downloaded from http://jme.oxfordjournals.org/ by guest on December 19, 2015
Repellent Cone
Fig. 2. Number of bites per 5 min on volunteers, plotted as a function of repellent concentration in (A) cotton and (B) polyester cotton fabrics. O O, DEPA; x x, DEET.
1 7 14 21 28 30 36 40 43
DEPA
January 1991
RAO ET AL.: IMPREGNATED FABRICS FOR MOSQUITO
145
REPELLENCY
5.0 I
A
Days
10
15
20
Days
Days
Fig. 3. Decay curve of DEPA showing half-life and leveling-off concentration for (A) polyester cotton, (B) cotton with a film-forming polymer, and (C) cotton in the absence of film-forming polymer. (D) Decay curve for DEET. O O, Polyester cotton; x x, cotton. lents. Using the McGovern & Schreck (1988) criteria, DEPA may be regarded as a very promising and effective compound. Studies conducted with DEPA-impregnated fabrics showed an effectiveness almost on a par with DEET against Ae. ae-
gypti. The half-lives of DEPA and DEET were the same in polyester cotton, whereas the half-life of DEPA was much less than DEET in cotton fabric. However, the leveling-off concentration was found to be almost the same on cotton fabric with both repellents. Therefore, it appeared that when filmforming polymers were added, a substrate-specific
quantity was firmly held and did not evaporate or inhibit repellency. Repellent-impregnated (in ethanolic solution) jackets have been evaluated in the United States and the USSR. The present study clearly indicated that in the absence of film-forming polymers, the treatment of fabric was effective only for a short duration; half the quantity of DEPA was lost within 2d. Gupta et al. (1987) studied the effectiveness of a controlled-release topical formulation of DEET (42% and 33%), and 0.12% permethrin-impregnated cotton or nylon fabric against 75% DEET formulation used by the U.S. Army. The authors
Table 2. Laboratory evaluation of detachable patches impregnated with DEPA against Ae. aegypti Days after treatment — 1 15 30 45 60 75-77 90 105
bites/5 min Control 33.0 43.5 38.0 52.0 45.5 47.0 42.0 40.0
DEPA patches 0.4 1.3 3.0 3.3 4.1 4.1 4.5 13.6
Mean no. bites/h
Days after treatment
Control
DEPA
1 15 30 45 60 75-77 90
40.0 31.2 33.1 30.0 39.3 33.3 30.0
1.6 2.4 4.0 5.4 11.0 11.0 16.4
% Prnfprtinn 96.0 92.3 88.0 82.0 72.0 67.0 45.6
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0.0
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JOURNAL OF MEDICAL ENTOMOLOGY
Vol. 28, no. 1
Gouck, H. K. & M. A. Moussa. 1969. Field tests with bed nets treated with repellents to prevent mosquito bites. Mosq. News 29: 263-264.
Received for publication 1 May 1989; accepted 10 July 1990.
Acknowledgment The authors thank K. M. Rao, Director, Research and Development Establishment, Gwalior, for his encouragement and interest in the work. The authors are grateful to P. K. Ramachandran, emeritus scientist, and H. C. Shrivastava, former Senior Deputy Director, Textile Industry Research Association, Ahmedabad, for valuable suggestions during the course of study.
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References Cited
Grothaus, R. H., J. M. Hirst, H. K. Gouck & D. E. Weidhaas. 1972. Field tests with repellent-treated wide-mesh netting against mixed mosquito populations. J. Med. Entomol. 9: 149-152. Gupta, R. K., A. W. Sweeney, L. C. Rutledge, R. D. Cooper, S. P. Fances & D. R. Westrom. 1987. Effectiveness of controlled release personal use arthropod repellent and permethrin-impregnated clothing in the field. J. Am. Mosq. Control Assoc. 31: 556-560. Itoh, T., G. Shuijo & T. Kurihara. 1986. Studies on wide-mesh netting impregnated with insecticides against Culex mosquitoes. J. Am. Mosq. Control Assoc. 2: 503-506. Kalyanasundaram, M., D. Amalraj, K. P. Pailey, G. Nisha & C. S. Sujatha. 1986. Synthesis of substituted amides for repellency against mosquitoes. Curr. Sci. 55: 266-268. Kumar, S., Shri Prakash, R. K. Sharma, S. K. Jain, M. Kalyanasundaram, R. V. Swamy & K. M. Rao. 1984. Field evaluation of three repellents against mosquitoes, black flies and land leeches. Indian J. Med. Res. 80: 541-545. Kurihara, T., K. Kamimura & R. Arakawa. 1986. Phenothrin impregnation of wide mesh net for protection against biting mosquitoes. Jpn. J. Sanit. Zool. 37: 261-262. Majori, G., G. Sabatinelli & M. Coluzzi. 1987. Efficacy of permethrin-impregnated curtains for malaria vector control. Med. Vet. Entomol. 1: 185-192. McGovern, T. P. & C. E. Schreck. 1988. Mosquito repellents. Monocarboxylic esters of aliphatic diols. J. Am. Mosq. Control Assoc. 4: 314-321. Prakash, S., S. S. Rao, S. Kumar & K. M. Rao. 1987. Studies on the effect of N,N-diethylphenylacetamide, an insect repellent on toxicity and reproduction in rats. J. Pharm. Sci. 49: 220-222. Prakash, S., S. Kumar, M.V.S. Suryanarayana, R. K. Sharma & K. M. Rao. 1988. Effectiveness of macrogol and talcum-based formulations of a new insect repellent N,N-diethylphenylacetamide. Int. J. Cosmet. Sci. 10: 23-28. Rao, S. S., S. Prakash, S. Kumar, U. Kaveeshwar, B. K. Bhattacharya, D. K. Jaiswal & K. M. Rao. 1987. Toxicological studies of an insect repellent, N,N-diethylphenylacetamide in rats. Indian J. Med. Res. 85: 626-633. Rao, S. S., S. Prakash & K. M. Rao. 1988a. Blood biochemical changes induced by insect repellent N,Ndiethylphenylacetamide in rats. Indian J. Med. Res. 88: 76-84. Rao, S. S., K. M. Rao & P. K. Ramachandran. 1988b. Chemistry efficacy and toxicology of insect repellents. J. Sci. Ind. Res. (India) 47: 722-736. Sharma, R. K., S. K. Jain, S. Kumar & K. M. Rao. 1984. Evaluation of some insect repellent formulations. Part I. Repellency against mosquitoes. Indian J. Hosp. Pharm. 21(26): 26-29. Shorey, H. H. & J. J. McKelvey, Jr. 1977. Chemical control of insect behaviour—theory and application. Wiley, New York. Snedecor, W. G. & W. G. Cochran. 1967. Statistical methods, 6th ed. Iowa State University Press, Ames.
did not find any superiority of the slow-release formulation over the current U.S. Army formulation of DEET. It is possible that the slow-release formulation was covalently bonded or bonded by physical forces (deep penetration), which affected the release of the repellent and decreased efficiency. Loading of chemical on the fabric was found to be an important point to be considered at the time of impregnation. Gouck & Moussa (1969) reported treatment of wide-mesh nets with DEET M-1960 at a concentration of 0.5 g repellent per g of net. These authors did not mention the effect of the chemical on the fabric. Our study clearly indicated that the application of DEPA or DEET to >15% of the weight of the fabric made the fabric sticky. Retention of repellent or insecticides in treated fabrics during washing was found to be another important consideration. Itoh et al. (1986), Kurihara et al. (1986), and Majori et al. (1987) reported that wide-mesh netting impregnated with a synthetic pyrethroid was effective. These authors did not mention the fastness of their impregnated fabrics after washing. In our study, the repellents rapidly lost efficacy and were not water-wash resistant. The application of insect repellent by patches circumvented this difficulty. Patches were effective for 90 d against Ae. aegypti in the laboratory and offered 67% protection for 77 d against Cx. quinquefasciatus in the field. Patches have many advantages. The treated patches do not come into direct contact with the skin. The patches can be removed when the uniform or garment is washed. The patches can be retreated by spraying. Application will be economical because only the comparatively small patches rather than the entire garment are treated by spraying. We are of the opinion that the same technique can be used for impregnation of widemesh head nets. Because DEPA also has been found effective against species of hematophagous insects other than mosquitoes (Kumar et al. 1984), the use of treated, detachable patches and anklets will be of value in providing protection against bloodsucking insects.
J. Med. Entomol. 28(1): 142-146 (1991) ABSTRACT The efficacy of fabrics impregnated with N,2V-diethylphenylacetamide (DEPA), a new repellent, was studied in the laboratory and field against Aedes aegypti (L.) and Culex quinquefasciatus Say. DEPA-treated polyester cotton and cotton fabrics provided repellency for 30 and 36 d and had a half-life of 11 and 5 d, respectively. The repellent could not be applied at a rate of > 15% of fabric weight. DEPA-treated fabric patches were found to be a practical and novel approach and were effective for 90 d in the laboratory against Ae. aegypti and 77 d in the field against Cx. quinquefasciatus. Insecta, repellents, mosquitoes, N,N-diethylphenylacetamide
of insect repellents directly to the skin gives protection for only a few hours because it is lost by evaporation, abrasion, and absorption (Shorey & McKelvey 1977). Topical application of repellents may not be cosmetically acceptable in hot and humid climates, especially in the northeastern regions of India, which are heavily infested with hematophagous insects and land leeches. The application of insect repellents to textiles is an alternative that provides longerlasting protection against these organisms. Repellent- and insecticide-impregnated clothing and wide-mesh netting have been found to be effective against hematophagous insects (Gouck & Moussa 1969, Grothaus et al. 1972, Gupta et al. 1987, McGovern & Schreck 1988). However, application of the chemical on fabrics should not affect the aesthetic properties of the cloth. N,N-diethylphenylacetamide (DEPA), a nontoxic, nonirritant, cosmetically acceptable, indigenously available, cost-effective, broad-spectrum repellent, has been developed recently (Kumar et al. 1984; Kalyanasundaram et al. 1986; Prakash et al. 1987, 1988; Rao et al. 1987, 1988a,b). Based on these extensive bioemcacy and toxicology studies, the Drug Controller of India (Ministry of Health) has issued a license for the manufacture of DEPA for use on humans. Because repellent textiles are a practical approach for protection against hematophagous insects, we report here the repellency of DEPAimpregnated fabrics based on slow-release technology. The duration of effectiveness of DEPA was THE APPLICATION
1 Defence Research and Development Establishment, Gwalior474002, India. 2 Ahmedabad Textile Industry Research Association, Ahmedabad 380015, India.
compared with N,N-diethyl-m-toluemide (DEET), a widely used repellent. Materials and Methods Test Chemicals. Two insect repellents were used. N,N-diethylphenylacetamide was synthesized in the laboratory (Sharma et al. 1984). DEET was obtained from M/s Fluka, Chemie AG Industriestrasse CH-9470 Buchs, Switzerland. Treatment of Fabrics. Printing and padding techniques were used for impregnating polyester cotton (2:1) and cotton fabrics with the insect repellents. Attempts to apply the repellents to the exterior surface of the fabric were abandoned because the thickeners were not compatible with the repellents or required elevated curing temperatures (130-150°C) which evaporated the repellents. Impregnation of the fabric by padding was of interest because the insect repellent was distributed uniformly. The padding recipe contained 10% repellent, 30% film-forming binder based on an acrylic copolymer (aminoacridine, copolymer Stryrene n-butylacrylate and methylol) (M/s Colourchem, Bombay, India), 6% fixer (melamine formaldehyde trimethylamine, 50% solution), 3% emulsifier, and 1% glacial acetic acid (acid-liberating catalyst which cured the binder at room temperature without loss of repellent). Evaluation of Repellency Against Mosquitoes.
The repellent activities of DEPA and DEET were evaluated by inserting a human hand covered with gloves or detachable patches into a test chamber (75 by 60 by 60 cm). The treated 150-cm2 surface was exposed for 5 min in the test chamber containing 200 Ae. aegypti (L.) females. The numbers of insects landing and biting were counted independently by two observers. Untreated fabric sam-
0022-2585/91/0142-0146$02.00/0 © 1991 Entomological Society of America
Downloaded from http://jme.oxfordjournals.org/ by guest on December 19, 2015
KEY WORDS
January 1991
RAO ET AL.: IMPREGNATED FABRICS FOR MOSQUITO REPELLENCY
143
pies were used as controls. Fabrics receiving fewer than five bites in 5 min (threshold) were considered to exhibit repellency. Observations were made twice weekly; however, the data are presented as weekly or fortnightly means. After ascertaining the effects of DEPA-impregnated fabrics and detachable patches in the laboratory, field trials using garments having five 10% DEPA-treated detachable patches were performed; four pieces (15 by 15 cm) were attached on the front and one patch (30 by 6.25 cm) on the back (Fig. 1 A and B). The patches were affixed by press buttons. The trials were carried out in a sylvan habitat of Gwalior from 1700 to 2200 hours. Seven subjects (four replicates) were used in each trial. Human volunteers wearing these garments were seated 1 m apart. Unprotected subjects wearing the garments without patches were exposed during each test period; the biting rate averaged 30-40 Culex quinquefasciatus Say per man-hour. The duration of effectiveness was determined at fortnightly intervals as percentage protection by comparing subjects with uniforms with and without patches. The trials were abandoned after protection from the patches decreased to 15% of the weight of the fabric because this concentration adversely affected the feel as well as the desirable properties of the cloth. Repellent-impregnated fabrics were found to lose their efficacy rapidly after washing with soap detergent in water. The concentration of repellent on day 5 after one washing was found to be 0.5% of the weight of the fabric; 20 bites of Ae. aegypti were recorded in a bioassay. Detachable Patches. DEPA-treated detachable patches were evaluated in the laboratory against Ae. aegypti and in the field against Cx. quinquefasciatus. Patches were effective for 90 d against Ae. aegypti in the laboratory. The data were statistically significant (F = 16.38; LSD, 2.59; P < 0.01) (Table 2). In the field, the treated patches offered 96% protection on day 1 against Cx. quinquefasciatus. However, the effectiveness of these patches decreased to 67% by day 77. The number of bites per hour on control volunteers was always statistically greater than on the volunteers who wore impregnated patches (F = 103.2; LSD, 4.4; P < 0.001) (Table 3). Discussion Two techniques were used for impregnating the fabrics. The padding method of impregnation was found to be superior because repellent and other ingredients were uniformly distributed and the loss of repellent during curing was minimal. McGovern & Schreck (1988) evaluated the effects of monocarboxylic esters and aliphatic diols on cotton stockings against mosquitoes. Effectiveness was based on the time until five bites were received. The authors considered compounds that provided protection for 11 d as promising repel-
Downloaded from http://jme.oxfordjournals.org/ by guest on December 19, 2015
Repellent Cone
Fig. 2. Number of bites per 5 min on volunteers, plotted as a function of repellent concentration in (A) cotton and (B) polyester cotton fabrics. O O, DEPA; x x, DEET.
1 7 14 21 28 30 36 40 43
DEPA
January 1991
RAO ET AL.: IMPREGNATED FABRICS FOR MOSQUITO
145
REPELLENCY
5.0 I
A
Days
10
15
20
Days
Days
Fig. 3. Decay curve of DEPA showing half-life and leveling-off concentration for (A) polyester cotton, (B) cotton with a film-forming polymer, and (C) cotton in the absence of film-forming polymer. (D) Decay curve for DEET. O O, Polyester cotton; x x, cotton. lents. Using the McGovern & Schreck (1988) criteria, DEPA may be regarded as a very promising and effective compound. Studies conducted with DEPA-impregnated fabrics showed an effectiveness almost on a par with DEET against Ae. ae-
gypti. The half-lives of DEPA and DEET were the same in polyester cotton, whereas the half-life of DEPA was much less than DEET in cotton fabric. However, the leveling-off concentration was found to be almost the same on cotton fabric with both repellents. Therefore, it appeared that when filmforming polymers were added, a substrate-specific
quantity was firmly held and did not evaporate or inhibit repellency. Repellent-impregnated (in ethanolic solution) jackets have been evaluated in the United States and the USSR. The present study clearly indicated that in the absence of film-forming polymers, the treatment of fabric was effective only for a short duration; half the quantity of DEPA was lost within 2d. Gupta et al. (1987) studied the effectiveness of a controlled-release topical formulation of DEET (42% and 33%), and 0.12% permethrin-impregnated cotton or nylon fabric against 75% DEET formulation used by the U.S. Army. The authors
Table 2. Laboratory evaluation of detachable patches impregnated with DEPA against Ae. aegypti Days after treatment — 1 15 30 45 60 75-77 90 105
bites/5 min Control 33.0 43.5 38.0 52.0 45.5 47.0 42.0 40.0
DEPA patches 0.4 1.3 3.0 3.3 4.1 4.1 4.5 13.6
Mean no. bites/h
Days after treatment
Control
DEPA
1 15 30 45 60 75-77 90
40.0 31.2 33.1 30.0 39.3 33.3 30.0
1.6 2.4 4.0 5.4 11.0 11.0 16.4
% Prnfprtinn 96.0 92.3 88.0 82.0 72.0 67.0 45.6
Downloaded from http://jme.oxfordjournals.org/ by guest on December 19, 2015
0.0
146
JOURNAL OF MEDICAL ENTOMOLOGY
Vol. 28, no. 1
Gouck, H. K. & M. A. Moussa. 1969. Field tests with bed nets treated with repellents to prevent mosquito bites. Mosq. News 29: 263-264.
Received for publication 1 May 1989; accepted 10 July 1990.
Acknowledgment The authors thank K. M. Rao, Director, Research and Development Establishment, Gwalior, for his encouragement and interest in the work. The authors are grateful to P. K. Ramachandran, emeritus scientist, and H. C. Shrivastava, former Senior Deputy Director, Textile Industry Research Association, Ahmedabad, for valuable suggestions during the course of study.
Downloaded from http://jme.oxfordjournals.org/ by guest on December 19, 2015
References Cited
Grothaus, R. H., J. M. Hirst, H. K. Gouck & D. E. Weidhaas. 1972. Field tests with repellent-treated wide-mesh netting against mixed mosquito populations. J. Med. Entomol. 9: 149-152. Gupta, R. K., A. W. Sweeney, L. C. Rutledge, R. D. Cooper, S. P. Fances & D. R. Westrom. 1987. Effectiveness of controlled release personal use arthropod repellent and permethrin-impregnated clothing in the field. J. Am. Mosq. Control Assoc. 31: 556-560. Itoh, T., G. Shuijo & T. Kurihara. 1986. Studies on wide-mesh netting impregnated with insecticides against Culex mosquitoes. J. Am. Mosq. Control Assoc. 2: 503-506. Kalyanasundaram, M., D. Amalraj, K. P. Pailey, G. Nisha & C. S. Sujatha. 1986. Synthesis of substituted amides for repellency against mosquitoes. Curr. Sci. 55: 266-268. Kumar, S., Shri Prakash, R. K. Sharma, S. K. Jain, M. Kalyanasundaram, R. V. Swamy & K. M. Rao. 1984. Field evaluation of three repellents against mosquitoes, black flies and land leeches. Indian J. Med. Res. 80: 541-545. Kurihara, T., K. Kamimura & R. Arakawa. 1986. Phenothrin impregnation of wide mesh net for protection against biting mosquitoes. Jpn. J. Sanit. Zool. 37: 261-262. Majori, G., G. Sabatinelli & M. Coluzzi. 1987. Efficacy of permethrin-impregnated curtains for malaria vector control. Med. Vet. Entomol. 1: 185-192. McGovern, T. P. & C. E. Schreck. 1988. Mosquito repellents. Monocarboxylic esters of aliphatic diols. J. Am. Mosq. Control Assoc. 4: 314-321. Prakash, S., S. S. Rao, S. Kumar & K. M. Rao. 1987. Studies on the effect of N,N-diethylphenylacetamide, an insect repellent on toxicity and reproduction in rats. J. Pharm. Sci. 49: 220-222. Prakash, S., S. Kumar, M.V.S. Suryanarayana, R. K. Sharma & K. M. Rao. 1988. Effectiveness of macrogol and talcum-based formulations of a new insect repellent N,N-diethylphenylacetamide. Int. J. Cosmet. Sci. 10: 23-28. Rao, S. S., S. Prakash, S. Kumar, U. Kaveeshwar, B. K. Bhattacharya, D. K. Jaiswal & K. M. Rao. 1987. Toxicological studies of an insect repellent, N,N-diethylphenylacetamide in rats. Indian J. Med. Res. 85: 626-633. Rao, S. S., S. Prakash & K. M. Rao. 1988a. Blood biochemical changes induced by insect repellent N,Ndiethylphenylacetamide in rats. Indian J. Med. Res. 88: 76-84. Rao, S. S., K. M. Rao & P. K. Ramachandran. 1988b. Chemistry efficacy and toxicology of insect repellents. J. Sci. Ind. Res. (India) 47: 722-736. Sharma, R. K., S. K. Jain, S. Kumar & K. M. Rao. 1984. Evaluation of some insect repellent formulations. Part I. Repellency against mosquitoes. Indian J. Hosp. Pharm. 21(26): 26-29. Shorey, H. H. & J. J. McKelvey, Jr. 1977. Chemical control of insect behaviour—theory and application. Wiley, New York. Snedecor, W. G. & W. G. Cochran. 1967. Statistical methods, 6th ed. Iowa State University Press, Ames.
did not find any superiority of the slow-release formulation over the current U.S. Army formulation of DEET. It is possible that the slow-release formulation was covalently bonded or bonded by physical forces (deep penetration), which affected the release of the repellent and decreased efficiency. Loading of chemical on the fabric was found to be an important point to be considered at the time of impregnation. Gouck & Moussa (1969) reported treatment of wide-mesh nets with DEET M-1960 at a concentration of 0.5 g repellent per g of net. These authors did not mention the effect of the chemical on the fabric. Our study clearly indicated that the application of DEPA or DEET to >15% of the weight of the fabric made the fabric sticky. Retention of repellent or insecticides in treated fabrics during washing was found to be another important consideration. Itoh et al. (1986), Kurihara et al. (1986), and Majori et al. (1987) reported that wide-mesh netting impregnated with a synthetic pyrethroid was effective. These authors did not mention the fastness of their impregnated fabrics after washing. In our study, the repellents rapidly lost efficacy and were not water-wash resistant. The application of insect repellent by patches circumvented this difficulty. Patches were effective for 90 d against Ae. aegypti in the laboratory and offered 67% protection for 77 d against Cx. quinquefasciatus in the field. Patches have many advantages. The treated patches do not come into direct contact with the skin. The patches can be removed when the uniform or garment is washed. The patches can be retreated by spraying. Application will be economical because only the comparatively small patches rather than the entire garment are treated by spraying. We are of the opinion that the same technique can be used for impregnation of widemesh head nets. Because DEPA also has been found effective against species of hematophagous insects other than mosquitoes (Kumar et al. 1984), the use of treated, detachable patches and anklets will be of value in providing protection against bloodsucking insects.
