Personal Protection

Personal Protection

Protective measures adopted by individuals and families not only help in protecting the individuals against mosquito bites and hence malaria, but also help in reducing the mosquito population by denying the blood meal essential for nourishment of the mosquito eggs in the female anopheles mosquito. Use of mosquito repellents, protective clothing and mosquito nets are important measures of personal protection against malaria. These are easy to use, safe and not very expensive. However, these should be used regularly without fail and therefore, demand such commitment form the users.

Mosquito repellents: Female mosquitoes bite human beings every 3 to 4 days for the blood meal and use visual, thermal, and most importantly, olfactory stimuli to locate a host. Carbon dioxide, released mainly from breath but also from skin, serves as a long-range airborne attractant and can be detected by mosquitoes at distances of up to 36 meters. Lactic acid, skin temperature, moisture, other volatile compounds, derived from sebum, eccrine and apocrine sweat, or the cutaneous microflora bacterial action on these secretions, may all act as attractants. Factors such as diet, general health condition, or reproductive status can also influence the odour profile of an individual and may explain the observed variation in human attractiveness to mosquitoes. In addition, floral fragrances from perfumes, soaps, lotions, and hair-care products may also attract mosquitoes and consumption of alcoholic drinks such as beer can also increase the attractiveness to mosquitoes. These attractants stimulate the chemoreceptors on the antennae of the mosquitoes and inhibition of these receptors by certain chemicals can produce mosquito repellent effect.Several synthetic and natural substances are being used as mosquito repellents. DEET (N,N-diethyl-m-toluamide [or N,N-diethyl-3-methylbenzamide]), picaridin (1-methyl-propyl 2-[2-hydroxyethyl]-1-piperidinecarboxylate [also known as KBR 3023]), PMD (p-menthane 3,8-diole [or oil of lemon eucalyptus]), MGK-326(dipropyl isocinchomeronate), MGK-264 (N-octyl bicycloheptane dicarboximide), IR3535 (ethyl butylacetylaminopropionate), and oil of citronella have been registered as insect repellents by the US Environmental Protection Agency.

Of these, DEET is the most effective, and best studied, synthetic insect repellent currently on the market. It has a remarkable safety profile after 40 years of worldwide use, although toxic reactions are known to occur. Developed by scientists at the U.S. Department of Agriculture and patented by the U.S. Army in 1946, it was subsequently registered for use by the general public in 1957. According to the estimates of the U.S. Environmental Protection Agency, more than 38% of the U.S. population uses a DEET-based broad-spectrum insect repellent every year and its worldwide use exceeds 200000000 people annually.DEET is available in 5% to 100% concentrations in multiple formulations, including solutions, lotions, creams, gels, aerosol and pump sprays, and impregnated towelettes. Products with 10% to 35% DEET will provide adequate protection under most conditions. Products with concentrations around 10% are effective for about two hours, concentration of 24% protects for about 5 hours and the efficacy plateaus at a concentration of about 30%. Generally DEET should be applied once a day and the lowest concentration effective for the amount of time spent outdoors should be chosen, especially for children. Use of 20% DEET is considered to be safe in pregnancy. In children, 30% DEET or less are considered to be safe, but these are not recommended for use in infants younger than 2 months.

Application of repellents: The repellents must be applied to lightly cover all exposed areas of skin; unprotected skin even a few centimeters away from a treated area can attract mosquitoes. It should be applied carefully over the face, avoiding contact with eyes and mouth. It should not be applied to children’s hands and after applying, repellent from the surfaces of the palms should be wiped off to prevent inadvertent contact with eyes, mouth, and genitals. Repellents should never be used over cuts, wounds, inflamed, irritated, or eczematous skin. Repellents may also be applied to clothing, window screens, mesh insect nets, tents, or sleeping bags. If DEET-treated garments are stored in a plastic bag between wearings, the repellent effect can last for many weeks.

Repellents containing DEET must be carefully applied because they can damage plastics (such as watch crystals and eyeglasses frames), rayon, other synthetic fabrics, leather, and painted or varnished surfaces. DEET does not damage natural fibers, such as cotton or wool, and has no effect on nylon. Using a DEET based insect repellent and a sunscreen together may reduce the sunscreen’s effectiveness.

How to apply mosquito repellents?

• Apply during the biting time of the mosquitoes; for anopheles, it is dusk to dawn.
• Take care to avoid contact with mucous membranes (eyes, nostrils, mouth, lips); do not spray on the face.
• Do not allow young children to apply this product; do not apply to hands or near the eyes and mouth of young children.
• Do not apply to sensitive, sunburned or damaged skin or deep skin folds.
• Use just enough repellent to cover exposed skin and/or clothing; do not use under the clothing.
• Avoid over-application.
• Wash the hands after applying the repellent.
• After returning indoors, wash treated skin with soap and water; wash treated clothing before wearing it again.
• In case of repellants formulated as sprays:
  • Do not spray in enclosed areas.
  • Do not spray directly onto face; spray on hands first and then rub on face.
• Repeated applications (every 3–4 hours) may be needed, especially in hot and humid climates.
• Strictly adhere to the manufacturers’ instructions and do not exceed the dosage, especially for young children.

Adverse effects of DEET: DEET is generally well tolerated, although there are some reports of unpleasant odor or greasy feel. After topical application, average dermal absorption of 100% DEET was about 5.6% and for 15% DEET in ethanol, an average of 8.4% of the dose was absorbed. Studies on DEET’s toxicity, mutagenicity and oncogenicity did not indicate any significant toxicities with normal use. Some cases of contact urticaria and irritant contact dermatitis (mostly in soldiers) have been reported; the ante-cubital fossa is particularly sensitive to developing bullous irritant contact dermatitis if DEET products are allowed to remain on this area overnight. There are stray reports of fatalities, altered mental state, rashes, skin or mucous membrane irritation, transient numb or burning lips, dizziness, disorientation, and difficulty concentrating, headache and nausea etc., following the use of DEET based repellents. The use of 20% DEET during the second and third trimesters of pregnancy did not increase any adverse neurologic, gastrointestinal tract, or dermatologic effects in infants through 1 year of age. A study by Malaria Research Centre, India revealed that of those using DEET-based cream, 11.4 per cent reported skin reaction and itching. If any adverse reaction to this product is suspected, its use should be discontinued and the treated skin should be washed.

Many plant derived insect repellents have also been tested: oils of citronella, cedar, verbena, pennyroyal, geranium, lavender, pine, cajeput, cinnamon, rosemary, basil, thyme, allspice, garlic, peppermint and neem have been reported to have repellent activity. But most of these studies are poor and most of these oils provided short-lasting protection, usually 20 minutes to less than 2 hours.

Other repellents: Many other types of repellents, such as mats, coils, lotions and vaporizers are also available, in the market. The current Indian market for these repellents is estimated to be more than Rs 500–600 crores (US$ 12–15 million) with annual growth of 7 to 10%. Allethrin, bioallethrin, d-allethrin, d-transallethrin, s-bioallethrin, prallethrin etc., are used in these mats, coils and vaporizers. These compounds vaporize without decomposition on heating at temperatures up to 400°C and produce varying repellent action on the mosquitoes, depending on the type of product and species of mosquito.

Mosquito Repellent Coil, Sticks, Mat and Liquid Vaporizer

Concerns have been raised about the safety of these products. In animal studies, these products have been reported to cause adverse effects on neurological, pulmonary, endocrinal and reproductive systems and to cause developmental impairment and cancers. A questionnaire-based survey among users of these products revealed that 11.8% users comprising all age groups and both sexes complained of a variety of acute toxicity, either soon after or within a few hours of using these repellents. Breathing problems were the most common (4.2%) and were frequently accompanied with headache or eye irritation or both. Pain in the ear and throat, cough, cold, running nose, wheezing, skin irritation etc., were also reported. Some coils containing pyrethroid insecticides, particularly d-allethrin, may contain octachlorodipropyl ether (S-2, S-421) as a synergist or active ingredient and the slow smoldering of the mosquito coils (about 8 hours/coil) may release bis(chloromethyl)ether (BCME), an extremely potent lung carcinogen.

Electronic mosquito repellents, ultrasonic devices, outdoor bug “zappers,” and bat houses are not effective against mosquitoes. Repellent-impregnated wristbands also do not offer any protection.

Air-conditioning: Although it has been said that air-conditioned rooms confer protection against mosquitoes, no systematic reviews or RCTs are available on the effects of air conditioning or electric fans to prevent malaria in travelers and some studies have even suggested that air conditioning does not offer any protection against anophelines.

Further reading:

1. Mark S. Fradin. Mosquitoes and Mosquito Repellents: A Clinician’s Guide. Ann Int Med June 1, 1998;128(11):931-940. Full text at http://www.annals.org/content/128/11/931.full.pdf+html
2. Lefèvre T, Gouagna L-C, Dabiré KR, Elguero E, Fontenille D et al. Beer Consumption Increases Human Attractiveness to Malaria Mosquitoes. PLoS ONE 2010;5(3): e9546. doi:10.1371/journal.pone.0009546. Full text at http://www.plosone.org/article/info:doi/10.1371/journal.pone.0009546
3. Chen LH, Wilson ME, Schlagenhauf P. Prevention of Malaria in Long-term Travelers. JAMA. 2006;296(18):2234-2244. Full text at http://jama.ama-assn.org/cgi/reprint/296/18/2234
4. Health Effects in Humans: DEET (N,N-Diethyl-meta-toluamide) – Chemical Technical Summary for Public Health and Public Safety Professionals. Agency for Toxic Substances and Disease Registry, Atlanta, Georgia. December 6, 2004. Available at http://www.atsdr.cdc.gov/consultations/deet/health-effects.html
5. Fradin MS, Day JF. Comparative efficacy of insect repellents against mosquito bites. N Engl J Med. 2002;347:13-18. Full text at http://content.nejm.org/cgi/reprint/347/1/13.pdf
6. Anderson RR, Harrington LC. Mosquito Biology for the Homeowner Available at http://www.entomology.cornell.edu/MedEnt/MosquitoFS/MosquitoFS.html
7. Malaria Research Centre. Bioenvironmental Strategy for Malaria Control: Plant Origin Repellents and Insecticides. Available at http://www.mrcindia.org/MRC_profile/alternate_strategy/plant_ins.pdf
8. http://www.epa.gov/pesticides/factsheets/chemicals/deet.htm
9. Schoepke A, Steflen R, Gvatx N. Effectiveness of personal protection measures against mosquito bites for malaria prophylaxis in travelers. Journal of Travel Medicine. 1998;5(4):188-192. Full Text at http://www3.interscience.wiley.com/cgi-bin/fulltext/119944385/PDFSTART
10. Harmful mosquito repellent. The Hindu. New Delhi, 2001 May 24. Available at http://www.indegene.com/Ent/Home/indEnt_Ind_News_26-05-2001_1.asp
11. Sharma VP. Health hazards of mosquito repellents and safe alternatives. Current Science. 2001;80(3):341-343. Full text at http://www.ias.ac.in/currsci/feb102001/341.pdf
12. Adanan CR, Zairi J, Ng KH. Efficacy and sublethal effects of mosquito mats on Aedes eegypti and Culex quinquefasciatus (Diptera: Culicidae). Proceedings of the Fifth International Conference on Urban Pests. Chow-Yang Lee and William H. Robinson (editors., Malaysia.2005. pp265-269. Available at http://www.icup.org.uk/reportsICUP041.pdf
13. Amalraj DD, Sivagnaname N, Boopathidoss PS, Das PK. Bioefficacy of mosquito mat, coil and dispenser formulations containing allethrin group of synthetic pyrethroids against mosquito vectors. J Commun Dis. 1996;28(2):85-93.
14. Amalraj DD, Kalyanasundaram M, Das PK. Evaluation of EMD vaporizers and bioallethrin vaporizing mats against mosquito vectors. Southeast Asian J Trop Med Public Health. 1992;23(3):474-8.
15. Krieger RI, Dinoff TM, Zhang X. Octachlorodipropyl Ether (S-2) Mosquito coils are inadequately studied for residential use in Asia and illegal in the United States. Environ Health Perspect 2003;111:1439–1442 doi:10.1289/ehp.6177. Full text at http://ehpnet1.niehs.nih.gov/members/2003/6177/6177.pdf
16. Enayati A, Hemingway J, Garner P. Electronic mosquito repellents for preventing mosquito bites and malaria infection. Cochrane Database of Systematic Reviews 2007, Issue 2. Art. No.: CD005434. DOI: 10.1002/14651858.CD005434.pub2. http://www.mrw.interscience.wiley.com/cochrane/clsysrev/articles/CD005434/pdf_fs.html
17. Soto J, Medina F, Dember N, Berman J. Efficacy of permethrin-impregnated uniforms in the prevention of malaria and leishmaniasis in Colombian soldiers. Clin Infect Dis. 1995;21(3):599-602.
18. Kimani EW, Vulule JM, Kuria IW, Mugisha F. Use of insecticide-treated clothes for personal protection against malaria: a community trial. Malaria Journal 2006;5:63. doi:10.1186/1475-2875-5-63. Full text at http://www.malariajournal.com/content/5/1/63
19. Macintyre K, Sosler S, Letipila F et al. A new tool for malaria prevention?: Results of a trial of permethrin-impregnated bedsheets (shukas) in an area of unstable transmission. International Journal of Epidemiology 2003;32(1):157-160. Full text at http://ije.oxfordjournals.org/cgi/reprint/32/1/157
20. World Health Organization. International travel and health: Situation as on 1 January 2010. WHO. Geneva. 2010. http://www.who.int/ith/ITH2010.pdf
21. Freedman DO. Malaria Prevention in Short-Term Travelers. NEJM. 2008;359(6):603-612. Full text http://content.nejm.org/cgi/content/full/359/6/603
22. Gahlinger PM, Reeves WC, Milby MM. Air Conditioning and Television as Protective Factors in Arboviral Encephalitis Risk. Am. J. Trop. Med. Hyg. 1986;35(3):601-610. Full text at http://www.ajtmh.org/cgi/reprint/35/3/601
23. Jaenson TG. Air conditioning does not stop malaria carrying mosquitoes. Lakartidningen. 1991;88(11):938.
24. http://www.andaman.org/book/Sane/Newsletter_2003-10/news_2003-10.htm
25. http://www.who.int/water_sanitation_health/resources/en/vector059to87.pdf
26. Octachlorodipropyl Ether (S-2) Mosquito Coils Are Inadequately Studied for Residential Use in Asia and Illegal in the United States
27. http://www.cdc.gov/malaria/control_prevention/vector_control.htm
28. Environ Health Perspect 111:1439-1442 (2003). doi:10.1289/ehp.6177 available via http://dx.doi.org/
29. Chen SC, Wong RH, Shiu LJ, Chiou MC, Lee H. Exposure to mosquito coil smoke may be a risk factor for lung cancer in Taiwan. J Epidemiol. 2008;18(1):19-25. http://www.jstage.jst.go.jp/article/jea/18/1/19/_pdf

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