An outbreak of Plasmodium falciparum malaria in U.S. Marines deployed to Liberia

Abstract

In 2003, 44 U.S. Marines were evacuated from Liberia with either confirmed or presumed Plasmodium falciparum malaria. An outbreak investigation showed that only 19 (45%) used insect repellent, 5 (12%) used permethrin-treated clothing, and none used bed netting. Adherence with weekly mefloquine (MQ) was reported by 23 (55%). However, only 4 (10%) had serum MQ levels high enough to correlate with protection (> 794 ng/mL), and 9 (22%) had evidence of steady-state kinetics (MQ carboxy metabolite/MQ > 3.79). Tablets collected from Marines met USP identity and dissolution specifications for MQ. Testing failed to identify P. falciparum isolates with MQ resistance. This outbreak resulted from under use of personal protective measures and inadequate adherence with chemophrophylaxis. It is essential that all international travelers make malaria prevention measures a priority, especially when embarking to regions of the world with high transmission intensity such as west Africa..

Conflict of interest statement

Disclosure: None of the authors have any potential conflicts of interest.

Figures

Figure 1.

Warehouse that housed U.S. Marines at Roberts Interactional Airport in Monrovia, Liberia demonstrating numerous risk factors for contracting an arthropod-borne illness including broken windows, persons sleeping on the roof, standing water, and tall grass in the surrounding area, for contracting an arthropod-borne illness. This figure appears in color at www.ajtmh.org.

Figure 2.

Flow diagram of U.S. Marines ashore in Liberia. † Doxycycline administered for malaria treatment and for possible co-infection with leptospirosis or rickettsial disease.

Figure 3.

Epidemic curve showing the onset of symptoms in days after first possible exposure in Liberia. † The symptoms this U.S. Marine reported on day 1 in Liberia were not considered related to malaria.