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Updated version:Statement on Personal Protective Measures to Prevent Arthropod Bites Volume 38 ACS- 3, November 2012
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Canada Communicable Disease Report
Volume 31 • ACS-13
1 December 2005
For readers interested in the PDF version, the document is available for download or viewing:
The Committee to Advise on Tropical Medicine and Travel (CATMAT) provides the Public Health Agency of Canada (PHAC) with ongoing and timely medical, scientific, and public health advice relating to tropical infectious disease and health risks associated with international travel. PHAC acknowledges that the advice and recommendations set out in this statement are based upon the best current available scientific knowledge and medical practices, and is disseminating this document for information purposes to both travellers and the medical community caring for travellers.
Persons administering or using drugs, vaccines, or other products should also be aware of the contents of the product monograph(s) or other similarly approved standards or instructions for use. Recommendations for use and other information set out herein may differ from that set out in the product monograph(s) or other similarly approved standards or instructions for use by the licensed manufacturer(s). Manufacturers have sought approval and provided evidence as to the safety and efficacy of their products only when used in accordance with the product monographs or other similarly approved standards or instructions for use.
There are blood feeding arthropods (insects and arachnids) that carry and transmit various pathogens, leading to diseases known as "arthropod-borne diseases" (ABDs). Usually, these pathogens complete a portion of their lifecycle within the arthropod vector before they can infect humans and are transmitted through the bite of the arthropod. Exceptions, however, include Chagas disease and louse-borne typhus, transmitted through feces defecated on the skin by the arthropod during feeding. Mosquitoes are considered to be the most important vector for ABDs (e.g. malaria and dengue), but many other types of arthropods transmit disease-causing pathogens(Footnote 1). Table 1 summarizes the information on the important arthropod vectors.
Unfortunately, there are preventive vaccines, chemoprophylactic drugs, or specific therapy for only a minority of ABDs. Even if vaccines or drugs are available, they are not totally effective, making measures to minimize insect bites an important way - and for some ABDs the only way - to reduce the risk to the traveller of acquiring ABDs . Many factors - such as the season, the time of day, and the preference for indoor or outdoor feeding - influence the feeding habits of arthropods(Footnote 1) (Table 1). Although knowledge of arthropod feeding habits would allow the traveller to significantly reduce ABD risk (e.g. when to stay indoors, when to apply repellent), arthropod behaviour is unpredictable. Reducing the risk for one ABD likely decreases the risk for others, because peak seasonality for transmitting ABDs in various geographic regions overlaps.
|Vector||Disease caused and pathogen(s) transmitted||Peak Biting Time/Activity|
|Usually bite between sunset and sunrise. Peak biting hours may vary. Some species prefer to bite indoors, while others prefer outdoors.|
|Aedes mosquitos||Yellow fever
|Usually bite during daylight hours, often outside, but some important vectors bite inside.|
West Nile virus
|Usually bite at night, often outdoors, but sometimes indoors.|
|Mansonia mosquitos||Filariasis||Usually bite at night, mostly outdoors.|
|Midges||Mansonellosis (usually an asymptomatic infection)||Bite at any time of day or night, usually outdoors.|
Relapsing fever (borreliosis)
Viral hemorrhagic fevers
|Widely dispersed in forest vegetation, meadows, and grassy environments; will wait on blades of grasses or branches of low bushes for passing hosts. A few species also live indoors.|
|Found indoors and outdoors, often associated with a specific type of host, but will feed on a variety of mammals (including humans).|
|Body lice||Relapsing fever (borreliosis)
|Usually found in clothing, except when feeding on human host.|
|Sand flies (Phlebotomus, Lutzomia)||Leishmaniasis
Sand fly fever
|Usually bite at night; many bite outdoors, but some also feed indoors.|
|Black flies (Simulium)||Onchocerciasis||Usually bite in the daytime, outdoors, in areas around rivers or streams.|
|Deer and horse flies (Tabanids)||Loa loa
|Active during the daytime outdoors, often during the sunniest hours; rarely feed indoors.|
|Tsetse flies (Glossina)||African Trypanosomiasis||Usually active during the daytime (though some important vector species are active at dusk or dawn) and usually bite outdoors.|
|Triatomine/ reduviid bugs||American Trypanosomiasis||Active at night and usually feed indoors on human blood.|
Arthropod bite prevention is maximized by using an integrated approach that includes the following "personal protective measures":
avoid arthropods (e.g. stay in an insect-proof area during the period of day when arthropods bite);
prevent arthropod bites by using:
physical barriers (e.g. clothing, bed net);
chemical barriers (e.g. repellents, insecticides)
Table 2 provides recommendations, as well as the evidence-based medicine (EBM) rating for each
|Measures for all travellers who are at risk of exposure to arthropod-borne infections
|Physical barriers for all travellers who are at risk of exposure to arthropod-borne infections
|All travellers at risk of exposure to serious arthropod-borne infections should appropriately use insect repellent containing DEET(Footnote 6,Footnote 7)-the preferred insect repellent, unless contraindicated (e.g. allergic reaction).||A I|
|For children, there are alternative personal protective measures:
|Extended duration (ED) DEET formulations have useful advantages over other formulations and, overall, are preferred(Footnote 15-Footnote 17). Where ED formulations are unavailable, products that contain up to 35% DEET are preferred.||B I|
|DEET and sunscreen combination products are not generally recommended(Footnote 18); however, if DEET and sunscreen application are both required, apply the sunscreen first, allowing skin penetration for 20 minutes, followed by DEET application (Canadian Dermatology Association).||A II|
|Avoid using repellents containing citronella oil(Footnote 7,Footnote 19).||E II|
|Consider P-menthane-3,8-diol (lemon eucalyptus oil) as a second-line alternative repellent, where DEET use is not possible (e.g. persons allergic to DEET)(Footnote 20).||A II|
|Consider soybean oil 2% "Blocker" repellents as a third-line repellent, where arthropod-borne infections present a significant risk(Footnote 7,Footnote 23).||A II|
|Bayrepel (KBR 3023, Autan), available in Europe(24), recommended by the World Health Organization(27) and registered with the Environmental Protection Agency (U.S.), may be as effective as 15% to 50% DEET(25,26). Repellents containing Bayrepel are not registered for use in Canada.||A II|
|For all travellers who are at risk of exposure to arthropod-borne infections:||A I
|Ineffective insect personal protection measures that are not recommended:
|All travellers should take, as directed, all prophylactic medications recommended for the prevention of arthropod-borne illnesses (such as malaria), regardless of personal protection methods used.||A I|
Minimize arthropod entry into work and accommodation areas. Place screens on windows and ensure that doors are in good repair and close properly and tightly, and check that walls and roof are without holes (C III - EBM recommendations).
Stay in an arthropod-protected area during the time(s) of day when local arthropods are actively biting (C III - EBM recommendations).
Avoid travelling to certain locales during the season when transmission of ABDs is most likely (C III - EBM recommendations).
If insects cannot bite, ABDs cannot be transmitted; it follows that aiming to reduce the amount of unprotected skin available to the arthropod is important.
There are both physical and chemical barriers to prevent bites:
Two types of chemical barriers reduce the risk of ABDs: repellents and insecticides. Repellents do not kill arthropods; rather, they produce an effect that causes the arthropod not to bite, whereas insecticides act primarily by killing an arthropod upon contact. These approaches are not mutually exclusive, and some chemicals have both effects, acting as a repellent and an insecticide.
There are several repellent active ingredients available for use in Canada and an even larger number available in other countries (Table 3). Repellents, available for sale in most (if not all) western nations, have been reviewed for effectiveness and safety on the basis of national regulations (in Canada, by Health Canada's Pest Management Regulatory Agency [PMRA] and in the United States, by the Environmental Protection Agency [EPA]). During testing, some repellents have been more effective (e.g. longer lasting repellency) than others against certain arthropod species.
Generally, the repellent DEET (N,N-diethyl-3-methyl- benzamide, also known as N,N-diethyl-m-toluamide) is acknowledged as the most effective repellent and is currently available on the Canadian market(Footnote 6,Footnote 7) (A I - EBM recommendations). DEET has been used as a repellent since 1954 by the U.S. military and is estimated to be applied several hundred million times yearly by North Americans alone. Scientific reviews have concluded that, when used as directed, DEET has an excellent safety record(6-14) (A I - EBM recommendations).
The higher the DEET concentration in the repellent formulation, the longer the duration of protection; however, this relation reaches a plateau at about 30% to 35%(Footnote 6). For a given DEET concentration, DEET formulations that are "extended duration" (ED), such as polymers, are generally considered to provide longer protection times and may be associated with less DEET absorption(Footnote 6,Footnote 7,Footnote 15-Footnote 17). The ED formulations are unavailable to the general public in Canada, but they are available in the U.S.
Regulatory agencies in western nations may differ in the recommended maximum concentration and application rates of DEET, especially for children. Health Canada's PMRA allows concentrations of up to 30% in Canada for persons aged >= 12 years. Those who are younger can use up to 10% DEET; for those aged 2 to 12 years, up to three times daily; and for children aged 6 months to 2 years, no more than once daily. The PMRA disallows the use of repellents containing DEET on infants under age 6 months(Footnote 6). However, CATMAT believes that, for travel outside of Canada where ABDs are endemic or epidemic and where exposure is likely and the risk for ABDs outweighs the risk of an adverse reaction to DEET, the threshold for use of DEET should be low. In fact, CATMAT recommends that travellers use DEET concentrations of up to 35% for travel outside of Canada.
For children, alternative personal protective measures, such as insecticide-impregnated mosquito nets, should be the first line of defence, especially for infants under age 6 months. Portable mosquito nets, including self-standing nets, placed over a car seat, a crib, playpen, or stroller, provide an insect-free environment for infants. However, as a complement to the other protection methods, the judicious use of DEET should be considered for children of any age. Recent medical literature from Canada suggests that DEET does not pose a significant or substantial risk to infants and children(Footnote 11).
The reapplication intervals on the labels of DEET formulations are a general guide only, because there are many variables - for example, sweating - that affect duration of repellency. As a general rule, the reapplication interval is a function of arthropod biting activity, so if biting is noted before the interval on the label has expired, then reapplication of DEET is recommended. DEET ED formulations have useful advantages over other formulations and, overall, are preferred when ABD risk is high(Footnote 15-Footnote 17) (A II - EBM recommendations).
DEET and sunscreen combination products are not generally recommended; DEET decreases the efficacy of sunscreens by 34%(Footnote 18). Further, the recommendations for application of DEET and sunscreen are opposite. Sunscreen should be used liberally and often, whereas DEET should be used sparingly and only as often as required. However, if application of both is required, the Canadian Dermatology Association recommends that the sunscreen be applied first and allowed to penetrate the skin for 20 minutes prior to applying DEET (A II - EBM recommendations).
|Active ingredient||Formulations||BrandsFootnote ¶||EfficacyFootnote * duration (hours)||Level of evidence|
|¶ These products are presented as examples only and are not necessarily endorsed by Health Canada.
* Most testing of repellency duration under field conditions is performed with Aedes species mosquitoes. Data regarding testing of DEET against Anopheles mosquitoes demonstrate shorter durations of efficacy, closer to the lower limits of the ranges in this table, compared with Aedes mosquitos(Footnote 6). Blackflies are repelled by very low concentrations of DEET for long durations(Footnote 6,Footnote 41). There are data supporting the efficacy of DEET as a repellent for ticks, but not enough information exists to calculate duration of efficacy(Footnote 6). Permethrin, applied only to clothing, has pesticidal, rather than repellent effects, against ticks and may therefore be more effective(Footnote 42,Footnote 43). There are limited data supporting the efficacy of DEET against deer flies and sand flies. Existing data support the ineffectiveness of DEET against fleas and lice(Footnote 6). Tsetse flies are effectively repelled by DEET(Footnote 44). Testing data for citronella oil and soybean oil are available only for Aedes species mosquitoes(Footnote 23), and testing data for p-menthane-3,8-diol and Bayrepel suggest equivalency of repellency between Aedes and Anopheles species mosquitoes(Footnote 20,Footnote 24-Footnote 26). The duration of efficacy ranges of DEET formulations are a general guide only, owing to many variables - for example, sweating - that affect duration of repellency. As a general rule, the duration of efficacy is a function of arthropod biting activity, so that if arthropod biting activity is noted, then reapplication of DEET is recommended.
|DEET < 10%||Pump spray, aerosol, gel, lotion||
|DEET 10% to 30%||Pump spray, aerosol, lotion, stick||
|DEET 20% to 35% Extended Duration||Lotion (polymer slow release)||
|Citronella oil 5% to 15%||Pump spray, lotion, oil, towelette||
|Lemon eucalyptus oil 10% to 30%||Lotion||
|Soybean oil 2%||Oil||
|Bayrepel 10% to 20% (Picaridin/ Hepidanin)||Pump spray, aerosol||
|Active ingredient||Formulations||BrandsFootnote ¶||Duration of efficacyFootnote ** (months)||Level of evidence|
|¶ These products are presented as examples only and are not necessarily endorsed by Health Canada.
* Data were based on studies of insecticide-treated mosquito nets used for the prevention of malaria in sub-Saharan Africa(Footnote 4,Footnote 5).
** Durations of efficacy do not apply to pyrethroid impregnation of clothing; deltamethrin residual efficacy was maintained after three to four washings of impregnated net,
whereas efficacy of other pyrethroids was lost after one to two washings.
|Permethrin EC 55%||Emulsified concentrate||Peripel||6||A I|
|Deltamethrin SC 1%||Suspension concentrate||K-Orthrine||12||A I|
|Deltamethrin 400 mg||Tablet||K-O Tab||12||A I|
|Lambda-Cyhalothrin CS 2.5%||Capsule suspension||Icon||9||A I|
|Cyfluthrin EW 0.05%||Water emulsion||Solfac||6-9||A I|
|Alpha-Cypermethin SC 10%||Suspension concentrate||Fendona||6-9||A I|
Most repellents containing "naturally derived," or synthetic analogues of "naturally-derived," materials are not considered the preferred products for protecting against arthropod bites. Oil of citronella products, for example, can repel mosquitoes, but the protection duration is very short (generally < 1 hour and often < 30 minutes)(Footnote 7). In fact, a recent analysis by Health Canada concluded that there are insufficient data to establish that the use of citronella repellents on skin does not pose an unacceptable risk to human health(Footnote 19). Citronella-containing repellents are therefore not recommended (E II - EBM recommendations). P-menthane-3,8-diol, a synthetic analogue of a lemon eucalyptus plant extract, is registered in Canada for use as an insect repellent ("OFF! Botanicals Lotion Insect Repellent 1")(Footnote 20). However, the period of protection afforded by this product (< 2 hours) is less than that for all but very low concentration (< 5%) DEET products. Besides, it is not approved for use on children < 3 years of age. Data indicate that it is reasonably effective against mosquitoes that carry malaria(Footnote 21,Footnote 22). Repellents that contain P-menthane-3,8-diol may be considered a second-line alternative repellent where DEET use is not possible (e.g. persons who are allergic to DEET) (A II - EBM recommendations).
Soybean oil 2% "Blocker" products are equivalent to 5% to 10% DEET in efficacy, repelling mosquitoes for 1 to 4 hours and blackflies for 5 to 10 hours(Footnote 7,Footnote 23). Soybean oil has low toxicity, has no age-associated use restrictions, and is non-irritating. Consequently, it may also be considered an alternative to DEET, albeit one with a substantially shorter protection time and without a long history of use. Importantly, CATMAT is unaware of scientific studies in which soybean repellents have been tested for effectiveness against tropical malaria vectors or for many other ABD vectors. Soybean repellents therefore are considered, at best, a third-line repellent where ABDs present a significant risk (A II - EBM recommendations). Although there are "Blocker" products containing soybean oil registered and approved for use in Canada (www.biteblocker.ca), they are not widely available in retail outlets.
Bayrepel, a piperidine derivative also known as "KBR 3023" and marketed under the trade name Autan, has been used in Europe for several years(Footnote 24). It has demonstrated action against various mosquito species, including those that carry the malaria parasite, with durations of protection, compared with 15% to 50% DEET(Footnote 25,Footnote 26) (A II - EBM recommendations). Toxicological analysis suggests no bioaccumulation, and rapid renal excretion with no significant toxicities was reported. Although recommended by the World Health Organization(Footnote 27) and registered with the Environmental Protection Agency (U.S.) in 2002, repellents containing Bayrepel have not been registered in Canada and are not available in the U.S. (www.autan.co.uk/index.html).
All travellers planning itineraries to foreign destinations that are endemic or epidemic for ABDs should be strongly encouraged to use pyrethroid (e.g. permethrin, deltamethrin, lambda-cyhalothrin, cyfluthrin, alpha-cypermethrin) insecticide-impregnated mosquito nets, unless their sleeping quarters are well screened or otherwise protected from mosquitoes(Footnote 14) (A I - EBM recommendations). Pyrethroids either kill arthropods directly after they land on impregnated netting or repel them. In either case, the end result is protection against arthropod bites and ABDs. Pyrethroid-impregnated nets are significantly more effective in preventing malaria than untreated nets and are safe for children and pregnant women(Footnote 4,Footnote 5) (A I - EBM recommendations). Duration of efficacy of pyrethroid-impregnated nets varies from several to 12 months, depending on the product used(Footnote 4) (Table 4 and Appendix 1). While pyrethroids are generally considered to be of low mammalian toxicity, care should be taken when impregnating the permethrin or an equivalent product into the net (e.g. follow the label instructions, use impervious gloves, and allow the net to dry before use) (Appendix 1). Pyrethroid treatments for bed nets are not registered by the PMRA for use by the general public. Insecticide-impregnated bed nets that are represented and sold for use in Canada require registration under the authority of the Pest Control Products Act (PCPA). However, the PMRA has an interim policy of not requiring the registration of either permethrin- or deltamethrin-impregnated bed nets if imported into Canada for sale to Canadians for use abroad.
Treating clothing with pyrethroid will also reduce the risk of ABDs (Appendix 2). Pyrethroid clothing treatments are not registered by the PMRA for use by the general public, but several products are available in the U.S. These products usually consist of 0.5% permethin in an aerosol or pump spray. Generally, clothing that is treated with the 0.5% permethrin aerosol or pump spray is effective at preventing arthropod bites for at least 2 weeks, assuming regular laundering practices (e.g. six machine washings)(Footnote 28,Footnote 29). More recently, outdoor clothing that was pre-treated with permethrin became available in the U.S. (e.g. clothing available under the trademark "Buzz-Off Insect Shield"). This pre-treated clothing is advantageous in that it maintains protective levels of permethrin through 25 or more machine washings (i.e. frequent retreatment is not required). Combining a long-acting DEET formulation that is applied to exposed skin and the pyrethroid-impregnated clothing enhances protection against biting arthropods(Footnote 30,Footnote 31) (A II - EBM recommendations).
There are additional products that are marketed as safe and "natural" and with effective measures to substantially reduce the risk of arthropod bites. However, CATMAT assesses some products as lacking in the sufficient scientific basis to recommend or as having the sufficient scientific basis to indicate the product's lack of usefulness (E II - EBM recommendations). These products include electronic (ultrasonic) devices(Footnote 32,Footnote 33), wristbands, neckbands, and ankle bands impregnated with repellents (whether for animal or human use)(Footnote 7,Footnote 34), electrocuting devices (i.e. "bug zappers")(Footnote 35,Footnote 36), odour-baited mosquito traps(Footnote 33,Footnote 37), the Citrosa plant (i.e. geranium house- plant)(Footnote 33,Footnote 38,Footnote 39), oral vitamin B1(Footnote 40), and skin moisturizers that do not contain an approved repellent active ingredient(Footnote 7).
Several personal protective measures exist to reduce the risk of acquiring ABDs. In fact, there is no single measure on which to rely that provides substantial confidence in protection; hence, CATMAT recommends and views as complementary the use of all measures.
This document is updated every 4 years or when new information becomes available.
Always use metric measurements: centimetre (cm), metre (m), millimetre (mm), millilitre (mL), and litre (L). Clean and dry all nets. Always wear protective gloves when soaking a net in insecticide.
1. Calculate the area of the net, in square metres.
Consider a conical net as a triangle and a rectangular net as two rectangles.
How to measure a mosquito net:
Lay the net flat to:
Hang up the net to:
2. Calculate the amount of water absorbed by the net, in millilitres or litres.
Using a bucket and a measuring container, measure two litres of water into the bucket. Soak the net until it is totally wet. Carefully wring out the net over the bucket. When the net has stopped dripping, measure the water remaining in the bucket.
For example: Original water in bucket (2 L) minus remaining water in bucket (1.3 L) = water absorbed by the net (0.7 L or 700 mL)
3. Calculate the amount of insecticide required.
|Compound and formulation||Dose (mg of active ingredient/ square metre)|
|Deltamethrin tablet||1 tablet per net|
To calculate the amount of insecticide use the following formula:
If you want a dosage of 200 mg/square metre on an 11 square metre net, using a product containing 50% permethrin w/w, calculate the amount required as follows:
If the net absorbs 0.7 L (700 mL) of water, add this amount of water to the insecticide to make a final mixture.
4. Wear protective gloves when treating nets with insecticide.
5. Measure the amount of water and insecticide needed.
Wide-mouth containers, such as an empty margarine container (1 kg = approximately 1 L), are best for measuring large amounts of water. Measure insecticide using a 250 mL empty container that can be scored inside at 50 mL intervals. For small amounts of insecticide, use a syringe.
6. Add the insecticide to the water and mix well.
Perform treatment outdoors or in a well-ventilated area. Alternatively, you can place the net in a plastic bag (ensuring that the bag contains no holes), then, add the insecticide and water solution, knead well, and remove the treated net from the bag for drying.
7. Dip the net in the solution until it is thoroughly wet.
8. Wring out the net over a bowl and hang up until it has stopped dripping.
9. Dry the net.
Wet nets can be laid out flat to dry. Avoid placing the net in direct sunlight for more than a few hours, because UV exposure may reduce the efficacy of the insecticide.
10. Wash your hands and all equipment with soap and water.
Triple rinse any containers for reuse, and punch holes in containers or equipment that will be discarded to prevent their reuse as drinking water containers.
11. Pour any waste insecticide down a pit latrine or into a pit dug into the ground, and NOT into a river or pond, because pyrethroids are highly toxic to fish and aquatic invertebrates.
Note: Prior to travelling, inquire about the availability of insecticide, and plan to purchase and apply these products at your destination. Pre-impregnated mosquito nets are available from PATH Canada on its Web site at http://www.pathcanada.org and are found in some travel and mountain equipment stores in Canada and in the U.S. These products are not currently registered by the PMRA.
For information regarding availability of insecticides in sub-Saharan Africa for application onto clothing or nets, visit the PATH Canada Web site at http://www.pathcanada.org.
Note: Prior to travelling, inquire about the availability of insecticide, and plan to purchase and apply these products at your destination. These products are not currently registered by the PMRA. For more information regarding application of insecticides onto clothing, please visit the permethrin Web site at http://www.permethrin-repellent.com.
* Members: Dr. B. Ward (Chairman); Dr. C. Beallor; M. Bodie-Collins (Executive Secretary); Dr. K. Gamble; Dr. S. Houston; Dr. Susan Kuhn; Dr. A. McCarthy; Dr. K.L. McClean; Dr. P.J. Plourde; Dr. J.R. Salzman.
Liaison Representatives: Dr. R.J. Birnbaum (CUSO); Dr. C. Greenaway (CIDS); Dr. C. Hui (CPS); Dr. R. Saginur (CPHA); Dr. P. Teitelbaum (CSIH).
Ex-Officio Representatives: Dr. R. Corrin (HC); Dr. B. Dobie (CIC); Dr. N. Gibson (DND); Dr. J. Given (HC); Dr. P. McDonald (HC); Dr. M. Parise (CDC); Dr. M. Tepper (DND).
Member Emeritus: Dr. C.W.L. Jeanes.