Prevention of Malaria, WWII Tactical and Technical Trends, No. 20: March 11, 1943 (Lone Sentry)

a. General

Malaria is caused by a small blood parasite and is spread only by the bite of the female Anopheles mosquito. The disease is widely distributed over all parts of the tropical and subtropical world and is also found in many of the more temperate regions. In times past, American troops have been faced with the problem of malaria not only in the southern United States, but also on posts of duty in Panama, Puerto Rico, Haiti, Nicaragua, and the Philippine Islands. World War II has carried United States forces to many new and different countries where malaria is present to an even greater degree. The disease is of tremendous tactical and medical importance in all the major theaters of operations, including the Southwest and South Pacific, India, and the Near and Middle East. Malaria will become increasingly important in North Africa following the rainy season, and the disease is ever present in Central Africa and in Central and South America. From the standpoint of prevalence and of the disability produced, malaria is the most important of all diseases in the world today.

Malaria mosquitoes breed under a variety of conditions. The most suitable locations are in slow-moving streams, swamps, lagoons, and marshes where water is either fresh or brackish (though some species have adapted themselves to breeding in salt water). Other potent carriers of malaria breed in small pools of still water, and in collections of rain water in hollows and depressions in the ground, such as borrow pits and hoofprints. Engineers frequently, though unintentionally, contribute to the breeding of mosquitoes and the spread of malaria by creating artificial breeding places during construction work. In dry, arid areas, anopheline mosquitoes have adapted themselves to desert conditions and are able to breed in mere trickles of water. They may also be found in large numbers about oases, irrigation canals, shallow wells, and ditches. Several varieties of malaria-carrying mosquitoes breed in small collections of water about houses, and, unless care is taken, may enter buildings through carelessly opened screen doors, torn screens, cracks, and the junctions of corrugated or tiled roofs with walls. While malaria and malaria mosquitoes are encountered most often in the lowlands, they may appear at altitudes up to 6,000 or 8,000 feet, as in Ethiopia and Iran, and in certain parts of India and China.

Anopheline mosquitoes usually feed between dusk and dawn but will remain in darkened hiding places during the day. Anophelines do not like wind and often seek the protection of dark rooms, outbuildings, and underbrush. They rarely fly more than 1 to 2 miles from breeding places. Small collections of water, or sluggish streams having a border growth of grass or rushes, are preferred by many species of anophelines for depositing eggs.

Man is the reservoir of the malaria parasite. Anopheline mosquitoes become infected when they feed on a human who has the disease. After the parasite has developed within the mosquito for a period of from 14 to 40 days these mosquitoes are capable of transmitting the infection. In heavily malarious areas as much as 80 percent of the population may be infected with the disease.

b. Preventive Measures

(1) Sleep in screened rooms or under mosquito nets. Inspect screens, doors, and mosquito nets at regular intervals, and search for live mosquitoes in those parts of the house where there is little light. Permanent buildings should be thoroughly screened. Screen doors should always open outward.

Entrance vestibules with a screened door at each end (mosquito lock) will prove invaluable in excluding mosquitoes from buildings.

(2) After dark, stay indoors in properly screened buildings as much as possible.

(3) When it is necessary to be out of doors after dark, move about continually. When advisable, use head nets, gloves, and leggings along with other mosquito-proof clothing covering the entire body. Mosquitoes are able to bite through the material ordinarily used in shirts and other lightweight clothing.

(4) Mosquito repellents should be applied to all exposed parts of the body at regular intervals. There are three good repellents (612, indalone, and dimethylphthalate) which are being issued by the Quartermaster. Of these, 612 will give good protection against mosquitoes for about 4 hours after liberal application, even under sweating conditions. Indalone will do about as well, except under sweating conditions, when it should be renewed half-hourly. Dimethylphthalate is slightly less effective than 612, but more effective than indalone. All are better than any repellents available heretofore.

(5) Insect sprays should be used inside airplanes and living quarters in the early morning and late afternoon, and at other times when necessary. The newly developed Freon pyrethrum aerosol insecticide spray is recommended.

(6) If possible, camps should be located on high, windswept ground, away from areas infested with mosquitoes and far removed from native villages (the inhabitants of which are usually infected and act as reservoirs of malaria). In permanent camps, control measures should include clearing, draining, and filling of low ground where possible, and all potential breeding places should be oiled or sprayed with Paris green as indicated (see S.G.O. Circular Letter 22, January 16, 1943).

(7) The use of quinine or atabrine for prophylaxis is not recommended as a routine procedure, since the available information indicates that these drugs do not prevent infection. They are, however, of definite military value in that they do prevent clinical symptoms of malaria so long as they are taken, and thus afford a means of keeping troops fit during periods of emergency in the field. Such drugs should be used only under special conditions and when advised by medical officers, flight surgeons, or local health authorities. The present War Department policy advocates atabrine 0.1 gram (one tablet or one and one-half grains) twice daily after meals on 2 days a week, allowing a 2- or 3-day interval between the days of taking. Under exceptional circumstances the dosage may be increased to two tablets on 3 days a week, still allowing an interval between days of taking. If atabrine is not available, take quinine sulfate 0.64 gram (2 tablets or 10 grains) after the evening meal each day (see S.G.O. Circular Letter 135, dated October 21, 1942).

(8) The estivo-autumnal, or malignant type of malaria, may give rise to unusual symptoms entirely different from the usual chills and fever. It is therefore advisable, when residing in, or travelling from, malarious areas, to suspect malaria when the cause of illness is unknown, regardless of whether there is fever or not. A physician should be consulted and advised of the recent possibility of exposure.

Comment: In the article in the previous issue - "Dangers" of the Tropics - reference was made to the problem of malaria, in a way that tended to "play down" the dangers from malaria, and also was written to apply to peacetime conditions.

The present report deals with the subject from the point of view of military medicine and, as such, should be considered as reflecting current Army medical opinion on this matter.

*Prepared in the Medical Intelligence Branch, Prevention Medicine Division, Office of the Surgeon General.