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As part of the framework of studies on personal protection against disease-transmitting mosquitoes, a field evaluation was carried out in a forest area of Cameroon on human subjects to assess the efficacy of a common repellent: DEET (a 50% active ingredient formulation). One ml of DEET applied to the legs of resting persons gave an 85% reduction in Anopheles bites during the 5 hours following application. The repellent effect decreased gradually with time. The effect was more than 90% maximum after 3 hours, 50% by about the seventh hour and declined to 0% from the fifteenth hour onwards. No difference was found between the three Anopheles species: Anopheles gambiae ss, An. nili and An. funestus. The longevity and infectivity of Anopheles populations caught on humans with repellent and on untreated controls were similar. Thus the reduction of biting rate can be considered equivalent to the reduction in malaria transmission. The effect of sweating on the loss of the applied repellent was studied. Moderate sweating, corresponding to normal activity, did not reduce the efficacy of the repellent. More profuse sweating did not significantly reduce repellent efficacy. We conclude that the tested formulation of DEET has the same efficacy as commercial formulations already on the market. Protection did not last the whole night, which is the time required for protection against malarial infection. However, good protection levels lasted more than 5 hours.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Evaluation of a DEET-based repellent on 3 vectors of malaria in central Africa]. 792

DEET remains one of the most effective repellents against a wide variety of insects. Although adverse reactions have been reported in the medical literature and magnified in the press, the compound is remarkably safe and has been used by hundreds of millions of people over the past 40 years. Permethrin is a better deterrent of ticks and, like DEET, is remarkably safe. Concomitant use of these two agents provides superior protection. Citronella and a bath oil, Avon Skin-So-Soft, also provide limited protection against some types of flying insects. The promise of new agents or protective strategies is on the horizon. Recently it was shown that retroviral vectors could be used to integrate and express foreign genes in the malaria mosquito, Anopheles gambiae. Conceivably, a genetically engineered mosquito that is resistant to malaria and other transmissible diseases may one day be developed, obviating some of the need for repellents. Almost certainly, future research will yield additional agents to further protect against mosquitoes.
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PMID:Insect repellents. What really works? 927 Jul 1

Chemoprophylaxis of malaria prevents the disease not the infection (suppressive chemoprophylaxis) with "high levels of confusion and low levels of compliance." The magnitude of danger of contracting malaria for travelers varies in several endemic zones. In West Africa, without prophylaxis, malaria is estimated to have an incidence of 1.4% per person per month. In South and Central America, the incidence is 0.05 and 0.01% per month, respectively. In Asia, the transmission and percentage of infection due to Plasmodium falciparum is much lower. The dangers of chemoprophylaxis in an area at low risk for chloroquine resistant P. falciparum are a reality. Incompletely active drugs change clinical manifestations, and changes in clinical manifestations delay the establishment of a correct diagnosis. The rate of adverse events is 15-20%, and hospitalization due to side effects of prophylaxis occurs in one in 10,000 travelers. Neuropsychiatric side effects have been reported with both mefloquine and chloroquine. A false sense of security can hinder a physician practicing in a nonendemic area from thinking of malaria when a traveler returns with fever. To complicate the picture, in many countries, there is an emerging drug resistance in P. falciparum as well as an emerging chloroquine resistance in P. vivax strains (20% in New Guinea and Irian Jaya). In short, no available chemoprophylaxis is free from toxicity, and its efficacy is never 100%. Alternatives to conventional chemoprophylaxis are encouraged in areas of low morbidity of malaria. In areas where P. vivax occurs primarily, and when the risk of serious side effects from chemoprophylaxis outweighs the risk of life threatening P. falciparum infection, there are four alternative strategies.2,3 The first strategy is that the traveler avoid mosquito bites. With a compulsive attitude, a high degree of protection can be realized with the proper use of pyrethrum-impregnated mosquito netting, topical DEET-containing insect repellents and impregnated protective clothing. Secondly, when the stay in malaria-endemic areas is less than 1 week, the disease will appear after returning home. No chemoprophylaxis is needed during the journey. With the onset of fever, diagnosis and therapy are performed without delay at home. This strategy assumes the participation of an informed physician. A third strategy is standby treatment, which is defined by the World Health Organization (WHO) as the use of antimalarial drugs carried for self administration when fever occurs and prompt medical attention is not available. Standby treatment is a safe option for an informed tourist traveling to areas at low risk of malaria or in areas where chemoprophylaxis may not be effective. Likewise, self therapy might be preferred for travelers who make frequent journeys characterized by brief and successive visits to malarious and nonmalarious areas, and for long-term travelers, and expatriots. Standby treatment minimizes drug overuse, demands early investigation of any febrile illness, and insists that effective treatment is given rapidly for P. falciparum malaria that occurs in nonimmune persons. This strategy is the responsibility assumed by teaching physicians and appears to be more advantageous than classic long-term chemoprophylaxis. A fourth strategy is systematic curative treatment carried out under supervision upon a traveler's return home. The administration of halofantrine after departure from endemic areas was studied for the prevention of P. falciparum malaria after short-term exposure,4 but the adverse cardiac effects of this drug obviates the usefulness of this "radical cure". Possibly the administration of doxycycline or azithromycin after departure from malarious areas could prevent P. falciparum malaria after short-term exposure and with less deleterious side effects. This approach requires more research, and again this will be the responsibility of physicians.
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PMID:Arguments against Chemoprophylaxis in Areas at Low Risk for Chloroquine-Resistant Plasmodium falciparum. 981 51

Several diseases are transmitted by hematophageous insect/arthropod and, except for yellow fever and Japanese B encephalitis, there are still no vaccines. Personal protection therefore remains the choice method for disease prevention and can usefully complete chemoprophylaxis if available (such as for malaria). Personal protection can be ensured by three main methods: avoiding risky areas; using repellents on skin and/or garments; using pyrethroids insecticide on garments (permethrin), mosquito nets (several Pyr. available) and any other materials (curtains etc.) including camping tents, plasting "UN sheeting" used in refugees camps etc. Repellent gave some protection for few hours (# 6 hours) and new formulations have been developed to extend their duration. Great care must be taken when using DEET which is not recommended for children and pregnant women. Coils and mats can be used but care must also be taken when using some coils available on local market and which can often be irritating and useless. Mosquito nets impregnated with an insecticide remains the choice method of protection against night-biting insects such as anopheles and is a good way of preventing malaria. Insecticide must be used according to safety measures clearly indicated (or which must be clearly indicated) by companies. All these measures are efficient and must be selected according to local conditions and human behaviour. Travelling is not "risky" but 3 points must be kept in mind: accurate advice must be sought before travelling; this advice must be followed while persuing a "normal life"; a physician must be consulted in case of any trouble during and after the trip.
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PMID:[Protection of travellers against biting arthropod vectors]. 1007 90

The protection against arthropods especially disease transmitting mosquitoes is becoming more and more important. The problems with drugs used for treatment and prophylactic of malaria are rapidly growing due to emergence of resistant parasites and unwanted side effects. Furthermore the population living in endemic area often can't afford the new expensive drugs. A safe and effective way of preventing insect bites is needed. One can prevent arthropod born diseases by avoiding insect bites through physical and chemical means or a combination of both. Repellents are substances applied to the skin, which effectively prevent insects from biting. The gold standard is still Diethylbenzamine (DEET), which is highly effective, well documented and in use for more than 50 years. The new repellent Bayrepel (hydroxyethyl isobutyl piperidin carboxylate) available to the consumer since 1998, seems to have an efficacy comparable with DEET. Insecticides have a direct toxic effect on the nervous system of arthropods. Mainly synthetic pyrethroids, which produce less ecological problems than the older products, are used. They are supplied in form of sprays, vaporising mats or coils. An important progress is the combination of insecticides with physical means. Insecticide treated bed nets or clothes give an excellent protection. Topical or systemic Vitamin B1, acoustic devices and electrocuters are still sold and widely used although their complete ineffectivity is documented in many studies.
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PMID:[Protection against biting mosquitoes]. 1144 93

Afrotropical malaria vectors of the Anopheles gambiae complex (Diptera: Culicidae), particularly An. gambiae sensu stricto, are attracted mainly to human hosts. A major source of human volatile emissions is sweat, from which key human-specific components are the carboxylic acids (E)- and (Z)-3-methyl-2-hexenoic acid and 7-octenoic acid. Electrophysiological studies on the antennae of An. gambiae s.s. showed selective sensitivity to these compounds, with a threshold at 10(-6) g comparable to that of known olfactory stimulants 1-octen-3-ol, p-cresol, isovaleric acid, and lower than threshold sensitivity to L-lactic acid and the synthetic mosquito repellent N,N-diethyltoluamide (DEET). A combination of the acids released at concentrations > 10(-5) g in wind tunnel bioassays significantly reduced the response to CO2, the major attractant released by human hosts, for strains of An. gambiae s.s. originating from East and West Africa. Field trials with odour-baited entry traps (OBETs) in Burkina Faso showed that 7-octenoic acid significantly increased (by 1.7-fold) the catch of females of An. gambiae sensu lato (comprising two sibling species: An. arabiensis Patton and An. gambiae s.s.) in OBETs baited with CO2, whereas combinations of the acids significantly reduced the catch in CO2-baited traps (by 2.1-fold) and in whole human odour-baited traps (by 1.5-fold). The pure (E) and (Z) geometric isomers of 3-methyl-2-hexenoic acid gave comparable results to the (EIZ) isomer mixture. These results provide the first experimental evidence that human-specific compounds affect the behaviour of highly anthropophilic An. gambiae s.l. mosquitoes. The compounds appear to inhibit the upwind flight' response to known long-range attractants, and may serve either to mask' the attractants present or, more probably, to 'arrest' upwind flight when mosquitoes arrive at a host under natural conditions. In the final approach to hosts, vectors are known to reduce their flight speed and increase their turning rate, to avoid overshooting the source. In our experimental apparatus, these changes in flight behaviour would reduce the number of mosquitoes entering the ports of the collection devices.
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PMID:Electroantennogram and behavioural responses of the malaria vector Anopheles gambiae to human-specific sweat components. 1158 42

We describe the British Army's current strategy for controlling arthropod vectors of disease during overseas deployments. Military commanders and medical officers have different, but complementary responsibilities in achieving vector control. In this paper we define a hierarchy of evidence-based vector control guidelines. Field guidelines must be based on the best available research evidence, preferably that derived from pragmatic randomised controlled trials (RCTs), and from systematic reviews of trials. Assessing the effectiveness of different vector control measures involves a trade-off between the relative benefits and harm of different technology options. There is compelling scientific evidence that bed nets and screens treated with a pyrethroid insecticide are highly effective in protecting against nocturnally active, anthropophilic arthropods (including ectoparasites), and will reduce the incidence of malaria, leishmaniasis, lymphatic filariasis and Chagas' disease. Etofenprox and deltamethrin are the safest pyrethroids, and permethrin the least safe. Vector control strategies of probable effectiveness are the use of insecticide-treated clothing, the wearing of protective clothing, and the correct use of DEET-based topical insect repellents. Aerosol insecticides are of debatable effectiveness. Other effective vector control measures, of limited usefulness during deployments, include electric fans, mosquito coils/vaporising mats, and smoke. "Biological" vector control measures, and insect buzzers/electrocuters are ineffective. Practical insect avoidance measures, based on an understanding of vector biology, complete the military vector-control arsenal. We conclude that practical insect avoidance measures, combined with pyrethroid-treated nets and clothing, and DEET-based topical repellents, can achieve almost 100% protection against biting arthropods.
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PMID:An evidence-based vector control strategy for military deployments: the British Army experience. 1158 66

The safety of daily application of N, N-diethyl-m-toluamide (DEET) (1.7 g of DEET/day) in the second and third trimesters of pregnancy was assessed as part of a double-blind, randomized, therapeutic trial of insect repellents for the prevention of malaria in pregnancy (n = 897). No adverse neurologic, gastrointestinal, or dermatologic effects were observed for women who applied a median total dose of 214.2 g of DEET per pregnancy (range = 0-345.1 g). DEET crossed the placenta and was detected in 8% (95% confidence interval = 2.6-18.2) of cord blood samples from a randomly selected subgroup of DEET users (n = 50). No adverse effects on survival, growth, or development at birth, or at one year, were found. This is the first study to document the safety of DEET applied regularly in the second and third trimesters of pregnancy. The results suggest that the risk of DEET accumulating in the fetus is low and that DEET is safe to use in later pregnancy.
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PMID:Safety of the insect repellent N,N-diethyl-M-toluamide (DEET) in pregnancy. 1169 70

The malaria vector Anopheles arabiensis Patton (Diptera: Culicidae) shows a marked predilection (> 80%) for biting the ankles and feet of human subjects, as revealed by our previous observations at Malahlapanga in the Kruger National Park, South Africa. Topical application of insect repellent, 15% deet (N,N-diethyl-3-methylbenzamide), to feet and ankles reduced the overall biting rate of An. arabiensis by 69%. A focal malaria epidemic in Albertsnek village (25 degrees 33'S, 31 degrees 59' E) near the Mozambique border, following flooding during February 2000, provided an opportunity to apply these findings of operational research for outbreak containment. Twice-nightly topical application of deet to ankles and feet of Albertsnek inhabitants was followed by rapid restoration of preepidemic malaria incidence levels after one incubation period. This encouraging outcome should be attempted in other outbreak-prone settings where infective mosquito bites are sporadic and malaria has unstable endemicity.
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PMID:Malaria outbreak control in an African village by community application of 'deet' mosquito repellent to ankles and feet. 1196 76

On April 29, 1997, in Suhum, Ghana, at the beginning of Malaria Awareness Month, Minister of Health Dr. Eunice Brookman-Amissah announced a 6-month accelerated malaria control program in 30 districts where the disease is most endemic; the program, which is sponsored by the World Health Organization (WHO), will continue until September 1997. The program is being launched because of the low impact of control efforts over the previous 4 years. Under the new program, health personnel, including 250 physicians in private and government employment, will be retrained regarding the proper management and treatment of malaria. In order to curtail the improper treatment of the disease, some chemical sellers and day care assistants will also be trained in the management and control of malaria. The next stage of the program will include measures to protect people from mosquito bites and to clear areas of mosquito breeding places.
Ghana Off News Bull
PMID:Malaria awareness month launched. 1229 6


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