Walking Well: Repel Arthropods

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Insect trouble time is now nearly upon us. What are all the problems they cause? How can we best deal with them? Insects are part of the phylum Arthropoda, a zoological classification of a large part of the animal kingdom. Arthropoda includes crustaceans, scorpions, ticks, mites, spiders, fleas, centipedes, and all the insects. Insects include cockroaches, lice, bed and other bugs, moths, bees, wasps, hornets, ants, flies, mosquitoes, and fleas.

The main arthropod-caused problems are stings, bites, and contact contamination. Stings are always painful and are dangerous when they cause severe allergic responses. Bites, while painful and irritating, are most serious because they transmit the tick-borne Lyme disease, Rocky Mountain spotted fever, and others, as well as mosquito-borne viral encephalitis. Cockroaches and flies cause food poisoning by contact-contamination. We will later discuss these in some detail giving their incidence, causation, symptoms, treatment, and prevention.

But first, how do you avoid arthropod contacts?

Avoid the areas they infest as much as possible. If it is not possible to totally miss these areas, at least hurry through them and don't camp there.

Exclude disease vectors and stingers and biters from direct contact by wearing protective clothing such as gaiters and head nets, and using tents with insect netting and sleeping indoors when possible. Smoke from campfires has some deterrent effect but is difficult to control.

Prevent the contamination of food by bacteria (Salmonella and Shigella) which are mechanically transferred by flies and cockroaches.

Use repellents to minimize skin contacts in infested areas.

What are the effective and ineffective repellents? How and when were they developed? What should we know about them?

The most effective and widely used current agent is diethyl toluamide (DEET). It was developed when jungle warfare needs in World War II spurred an intensive research program by the Department of Agriculture. This search first yielded the effective ethohexadiol (Rutgers 612) in 1942, dimethylphthalate in 1948, and finally the best compound, diethyl toluamide. DEET has supplanted the earlier repellents.

Oil of citronella (the active ingredient citronellal has been known since 1899, structure determined in 1958), an old remedy that I used on my first overnight hike, is not very effective, although some people still buy large citronella-containing candles for outdoor protection.

Pyrethrins, isolated from pyrethrum flowers in 1924, led to permethrin (Permanone, Ambush, Dragnet, Pounce), which is both an insecticide and a repellent.