Malaria prevention in travelers.

The prevention of malaria in travelers is becoming a more challenging clinical and public health problem because of the global development of drug-resistant Plasmodium strains of malaria and the increasing popularity of travel to exotic locales. Travelers can reduce their risk of acquiring malaria by using bed netting, wearing proper clothing and applying an insect repellent that contains N,N-diethyl-meta-toluamide. Chloroquine, once the standard agent for weekly malaria prophylaxis, is no longer reliably effective outside the Middle East and Central America because of the emergence of resistant Plasmodium falciparum strains. Mefloquine is now the most effective and most recommended antimalarial agent on the U.S. market; however, the side effects of this agent have begun to limit its acceptance. Doxycycline is effective for malaria prophylaxis in travelers who are unable to take mefloquine. Daily proguanil taken in conjunction with weekly chloroquine is an option for pregnant patients traveling to sub-Saharan Africa. Terminal prophylaxis with two weeks of primaquine phosphate can eliminate an asymptomatic carrier state and the later development of malaria in newly returned long-term travelers with probable exposure to Plasmodium vivax or Plasmodium ovale. Travelers who elect not to take an antimalarial agent or who are at high risk for malaria and are more than 24 hours from medical care can use self-treatment regimens such as those featuring pyrimethamine-sulfadoxine. Conventional agents may be contraindicated in certain travelers, especially pregnant women and small children, and several prophylactic agents are not available in the United States. Azithromycin and a number of malaria vaccines are currently under investigation.