Controversies and misconceptions in malaria chemoprophylaxis for travelers

Abstract

Context: Controversies in malaria prevention arise from the absence of data, conflicting data between different studies, conflicting recommendations, deviation of local practice from scientific data, and varying risk thresholds. Misconceptions about the seriousness of malaria, the tolerability of chemoprophylaxis drugs, and the efficacy and safety of repellents contribute to the controversies.

Objectives: To compare several national guidelines on malaria chemoprophylaxis to identify variations in recommendations. We reviewed studies on tolerability of mefloquine with particular focus on its neuropsychiatric adverse effects and influence on performance. We also describe why most recommended chemoprophylactic regimens fail to prevent relapses of Plasmodium vivax malaria and review available options.

Evidence acquisition: We searched scientific publications in MEDLINE via PubMED for relevant articles with a cutoff date of December 2006 using the search terms malaria, chemoprophylaxis, travel, mefloquine, neuropsychiatric adverse events, tolerability, vivax malaria, and primaquine. Additional references were obtained from bibliographies of the selected articles. There were no language restrictions.

Evidence synthesis: Gaps and conflicts exist among current guidelines. Health authorities vary in the chemoprophylaxis drugs they recommend, the indications for continuous prophylaxis vs no prophylaxis, and the use of standby emergency treatment. Despite widespread reports on the adverse effects of mefloquine, controlled studies found that serious neuropsychiatric adverse events occur at rates comparable with or lower than other chemoprophylaxis drugs. Moreover, mefloquine does not appear to impair performance while driving, flying, or diving. Vivax malaria causes significant illness in travelers, but current first-line chemoprophylaxis agents do not prevent relapses of vivax malaria. Although not licensed in most countries as primary prophylaxis, primaquine effectively prevents relapses of vivax malaria.

Conclusions: Prevention of malaria in travelers requires detailed knowledge of malaria epidemiology and host-vector-parasite interactions. Decisions are complicated by a lack of standardized recommendations, controversies, and misconceptions. Improved international consensus is indicated to minimize conflicting guidelines, clarify controversies, and promote adherence to preventive measures.