Malaria in the Traveler: How to Manage Before Departure and Evaluate Upon Return

Abstract

Malaria is the clinical syndrome when a patient experiences symptoms in response to infection with one of several strains of the Plasmodium parasite. This article is intended for health care providers to become familiar with some of the basics of care of patients who are travelling to or returning from an area with ongoing malaria transmission. The specific focus is on patients from nonendemic areas who plan on travel for a finite period to an area where malaria is endemic.

Keywords: Chemoprophylaxis; Fever in returning traveler; Malaria; Plasmodium; Prevention.

Figure 1. Malaria Life Cycle

The malaria parasite life cycle involves two hosts. During a blood meal, a malaria-infected femaleAnopheles mosquito inoculates sporozoites into the human host . Sporozoites infect liver cells and mature into schizonts , which rupture and release merozoites . (Of note, in P. vivax and P. ovale a dormant stage [hypnozoites] can persist in the liver and cause relapses by invading the bloodstream weeks, or even years later.) After this initial replication in the liver (exo-erythrocytic schizogony ), the parasites undergo asexual multiplication in the erythrocytes (erythrocytic schizogony ). Merozoites infect red blood cells . The ring stage trophozoites mature into schizonts, which rupture releasing merozoites . Some parasites differentiate into sexual erythrocytic stages (gametocytes) . Blood stage parasites are responsible for the clinical manifestations of the disease. The gametocytes, male (microgametocytes) and female (macrogametocytes), are ingested by anAnopheles mosquito during a blood meal . The parasites’ multiplication in the mosquito is known as the sporogonic cycle . While in the mosquito's stomach, the microgametes penetrate the macrogametes generating zygotes . The zygotes in turn become motile and elongated (ookinetes) which invade the midgut wall of the mosquito where they develop into oocysts . The oocysts grow, rupture, and release sporozoites , which make their way to the mosquito's salivary glands. Inoculation of the sporozoites into a new human host perpetuates the malaria life cycle. From Centers for Disease Control and Prevention. About malaria. Available at: http://www.cdc.gov/malaria/about/biology/. Last accessed Aug 26 2015; with permission.

Figure 2. Rapid Diagnostic Test for Malaria

Some training is required to perform and interpret this assay, but much less than for blood smears. © 2015 Alere. All rights reserved. BinaxNOW is a trademark of the Alere group of companies. Photo permission granted by Alere.

Figure 3. Thin smear of P.falciparum malaria

Note high burden of parasites which look like signet rings or headphones within multiply-infected normal-sized erythrocytes, all hallmarks of P.falciparum.