Nearly 30,000 travelers from Europe and North America contract malaria each year. Keeping abreast of the latest recommendations for malaria chemoprophylaxis can be daunting. Lobel and Kozarsky reviewed the malaria prophylaxis guidelines of the Centers for Disease Control and Prevention and the World Health Organization.

Travelers to sub-Saharan Africa, Papua New Guinea, the Solomon Islands and Vanuatu are at highest risk of contracting malaria, while those traveling to Haiti and the Indian subcontinent are at intermediate risk. The risk is low in most of Southeast Asia and Latin America. Plasmodium falciparum, Plasmodium vivax, Plasmodium ovale and Plasmodium malariae are the four species that cause malaria. Malaria caused by P. falciparum can be fatal if it is not promptly treated.

In addition to chemoprophylaxis, various preventive measures may be taken. These include staying in air-conditioned or well-screened rooms from dusk until dawn, using aerosol insecticides, using mosquito netting and applying N, N-diethyl- m-toluamide (DEET)–containing insect repellents on exposed skin. The repellent should contain less than 30 percent DEET, since higher DEET concentrations may be associated with more toxic effects.

The spread of resistance to various chemo-prophylactic regimens has rendered some drugs much less effective in certain areas of the world. Chloroquine-resistant P. falciparum malaria was first encountered in the 1960s and has spread to most malaria-endemic countries, except Haiti, the Dominican Republic, Central America (west of the Panama Canal) and parts of the Middle East. P. falciparum malaria has also demonstrated resistance to the combination drug pyrimethamine–sulfadoxine in Southeast Asia, Africa and the Amazon region, and resistance to mefloquine in western Cambodia and in the regions of the Thai–Myanmar and Thai–Cambodian borders.

Travelers to areas where chloroquine-resistant malaria occurs should receive mefloquine (see the accompanying table). Mefloquine can be taken by pregnant women and young children. If mefloquine is contraindicated, such as in patients with an underlying neuropsychiatric or seizure disorder, doxycycline prophylaxis is recommended (except in pregnant women and children younger than eight years of age). However, doxycycline is much less effective than mefloquine, and compliance with daily doses of doxycycline may be much lower than compliance with weekly doses of mefloquine.

Chloroquine is still recommended for travelers to areas where chloroquine-resistant malaria has not been reported. This agent can be given to pregnant women and children.

Mefloquine or chloroquine prophylaxis should be initiated one to two weeks before the trip. Doxycycline prophylaxis can be initiated one or two days before the trip. Prophylaxis with mefloquine, chloroquine or doxycycline should continue for four weeks after the patient leaves the area. Primaquine, which is recommended for “terminal prophylaxis” (prophylaxis after travel) to prevent relapsing malaria, should not be taken for more than 14 days.

The authors conclude that none of these treatments is completely effective, so malaria should be included in the differential diagnosis of any ill patient who has returned from a malarious area, even if the patient was compliant with the prophylactic regimen.