JOURNAL OF THE LOUISIANA STATE MEDICAL SOCIETY
Malaria Prophylaxis
James H. Diaz, MD, MPH & TM, DrPH
Malaria, the world’s third leading cause of infectious disease deaths, is most commonly imported into the United States (U.S.) by travelers returning from malaria-endemic regions without taking chemoprophylaxis. As a result, the objectives of this review included: (1) to describe the current epidemiology of malaria in the U.S.; (2) to identify the sites of action of antimalarials in the parasite’s life cycle; (3) to review current recommendations for chemoprophylaxis for short-term travelers (≤ 3 weeks); (4) to discuss recent controversies in chemoprophylaxis; and (5) to review current progress towards the primary prevention of malaria by vaccination. Only chemoprophylaxis withmefloquine, atovaquone-proguanil, or doxycyclinewill preventmost attacks by chloroquine-resistant P. falciparum . Only primaquine can interrupt the hypnozoite stages of P. vivax and P. ovale and prevent relapsing malaria. The most significant controversies in malaria chemophylaxis today include the safety of mefloquine, the duration of atovaquone-proguanil post-travel, and primaquine for primary prophylaxis. Although contraindicated in travelerswithneuropsychiatric disorders,mefloquine is cost-effective for long-termtravelers and safe throughout pregnancy. Only larger studies can confirm an abridged post-travel schedule for atovaquone-proguanil shortened from one week to one day. Primaquine should be reserved for relapse prevention caused by P. vivax and P. ovale . Personal protectivemeasures against malaria including topical insect repellents and mosquito bite avoidance are always recommended since no chemoprophylactic regimen is 100% preventive. The complex life cycle of the Plasmodium species in two hosts complicates antigenic targeting for the most effective malaria vaccines.
INTRODUCTION
METHODS
After tuberculosis and human immunodeficiency virus (HIV), malaria is the third leading cause of infectious disease deaths in the world causing 300-500 million cases and up to 2.7 million deaths annually. 1 Malaria is transmitted by bites from infected female Anopheles mosquitoes and results from systemic infection with one of five protozoans of the genus Plasmodium . Human infectious species include P. falciparum, P. vivax, P. ovale, P. malariae , and, rarely, the simian species, P. knowlesi. Anopheles mosquitoes are widely distributed globally and capable of transmitting malaria to about half of the world’s population (Figure 1). Although transmission of malaria typically occurs by mosquito bites, human-to-human transmission may also occur by congenital infections, blood transfusions, organ transplants, and percutaneous and nosocomial exposures. Malaria-infected persons in the United States (U.S.) are typically travelers returning frommalaria-endemic regionswithout taking preventive measures, including oral prophylactic medications and topical mosquito repellents. Although relapsing P. vivax malaria transmitted locally by A. quadrimaculatus was the most common type of malaria in the U.S. until the 1950s, most cases of malaria in the U.S. today are imported by international travelers, not locally transmitted, and caused by the most virulent and potentially lethal strain, P. falciparum . 2 As a result, the objectives of this review were: (1) to describe the current epidemiology of malaria in the U.S.; (2) to identify the sites of action of antimalarials in the parasite’s life cycle; (3) to review current recommendations for chemoprophylaxis for short- term travelers (≤ 3 weeks); (4) to discuss recent controversies in chemoprophylaxis; and (5) to review current progress towards the primary prevention of malaria by vaccination.
Internet search engines including PubMed, Medline, Ovid, Google®, Google Scholar®, and Cochrane were queried with the keywords as medical subject headings to meet the objectives of this narrative review. The keywords included malaria, chemoprophylaxis, prevention; drugs, vaccines, antimalarial; parasites, Plasmodium species; mosquitoes, Anopheles species; travel, travelers, short-term. Short-term travel was defined as three weeks or less in a malaria-endemic region of the world (Figure 1). The study period was defined as 1990-2017. The articles selected to meet the first three objectives included review articles, case series, observational, longitudinal, and surveillance studies. The articles selected to meet the last two objectives to identify peer-reviewed scientific articles on current
Malaria Risk No Malaria
Figure 1: World Regions with Endemic Malaria. Source: Wikimedia Commons. No copyright permission required.
J La State Med Soc VOL 169 SEPTEMBER/OCTOBER 2017 131
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