JOURNAL OF THE LOUISIANA STATE MEDICAL SOCIETY
Figure 2: The Life Cycle of Malaria Infections with Plasmodium Parasites. Source: US Centers for Disease Control and Prevention (CDC).
areas and will also prevent primary attacks by non-falciparum species, but not relapsing attacks by P. vivax or P. ovale . 1, 4
due to widespread resistance.
Since chemoprophylactic strategies are not 100% effective in preventing malaria, they will always require support by personal protective measures designed to (1) reduce exposed skin to mosquito bites outdoors by wearing light-colored, long-sleeved shirts, socks, and long pants; (2) limit the number of mosquito bites by applying effective topical insect repellents and wearing permethrin-impregnated clothing; and (3) interrupt Anopheles - preferred nocturnal feeding times by sleeping in air-conditioned accommodations or within permethrin-treated bed nets or hammocks. Current Controversies in Malaria Chemoprophylaxis for Short-term Travelers The Safety of Mefloquine Mefloquine, available since the late 1980s, is a 4-aminoquinolone compound related toquinine like chloroquine that interrupts the blood phases of the malaria parasite without affecting the liver stages including the hypnozoite stages of P. vivax and P. ovale . 12 Although not a heme polymerase inhibitor like chloroquine, mefloquine exerts its antimalarial actions in a similar manner by competing with the parasite for heme binding within the erythrocyte.Unlikechloroquineresistance,mefloquineresistance is not widespread and remains primarily restricted to isolated regions along Thailand’s borders with Cambodia and Myanmar (formerly Burma). Mefloquine has the same administration schedule as chloroquine and has now replaced chloroquine for chemoprophylaxis in most P. falciparum -endemic regions. The safety of mefloquine chemoprophylaxis in short and long- term travelers has received increased attention because of rare behavioral and neuropsychiatric adverse reactions. 13
Chloroquine remains available in the U.S. and is effective for most non- falciparum species with the exception of chloroquine- resistant P. vivax in Papua New Guinea and Indonesia. Until recently, chloroquine chemoprophylaxis for chloroquine- sensitive P. falciparum malariawas also recommended for visitors to the island of Hispaniola. In 2009, however, chloroquine- resistant P. falciparum malaria was first detected in Haiti, and chloroquine chemoprophylaxis for P. falciparum malaria is no longer recommended in Haiti. 11 As noted, only two antimalarials, atovaquone-proguanil and primaquine, can interrupt both liver (exoerythrocytic) and blood (erythrocytic) stages of the parasite’s life cycle and require shorter durations of therapy with increased patient compliance, especially post-travel. Only primaquine can interrupt the latent hepatic or hypnozoite stages of P. vivax and P. ovale and prevent relapsing malaria if administered presumptively (presumptive relapse prevention therapy) or for cause (terminal prophylaxis) or cure (radical curative therapy) after travel for 14 days. Only primaquine is gametocidal and capable of killing the sexual stage gametocytes in the circulation. Table 2 compares all of the recommended oral medications for malaria chemoprophylaxis in short-term (three weeks or less) travelers as stratified by adult and pediatric dosages, administration schedules, and potential major adverse effects. Although sold as effective antimalarials in some malaria- endemic countries, sulfadoxine/pyrimethamine, proguanil, chloroquine/proguanil, and hydrochloroquine are no longer available in the US or even recommended for chemoprophylaxis
134 J La State Med Soc VOL 169 SEPTEMBER/OCTOBER 2017
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