Malaria Among U.S. Military Personnel Returning from Somalia, 1993

U.S. military personnel were first deployed to Somalia in late December 1992 as part of Operation Restore Hope. From the time of deployment through April 1993, malaria was diagnosed in 48 personnel who had onset of illness while in Somalia. In addition, through late June, malaria was diagnosed in 83 military personnel following their return from Somalia. This substantial number of cases has reinforced concerns regarding malaria prophylaxis, the estimated risk for infection, and the need for prompt recognition and treatment of malaria in military personnel. This report summarizes the occurrence of malaria in returning personnel and underscores for health-care providers the importance of considering malaria in the diagnostic evaluation of military personnel returning from Somalia and in other persons who have traveled to malarious areas.

Malaria infections were documented in 21 Marine and 62 Army personnel, all of whom had onset of illness after returning to the United States. Of the 62 Army personnel, 55 (89%) were stationed at Fort Drum, New York; approximately 60% of all Army troops sent to Somalia originally were stationed at Fort Drum. Detailed investigations have been completed for 32 (58%) of the Army personnel stationed at Fort Drum and all 21 Marines. Of these 53 persons, 43 (81%) had been stationed south of Mogadishu. Plasmodium vivax was detected in 41 (77%) of the cases, P. falciparum in nine (17%), a mixed vivax and falciparum infection in two (4%), and P. ovale infection in one.

Mefloquine was used for malaria prophylaxis by 38 persons and doxycycline by 15 persons. Because of the reportedly low frequency of vivax and ovale malaria in Somalia, terminal prophylaxis with primaquine to prevent relapses of vivax or ovale malaria following departure from Somalia had not been recommended for Army personnel. Although terminal prophylaxis had been recommended for Marine and Navy personnel, only eight of the 15 Marines with vivax or ovale malaria had completed terminal prophylaxis. Use of prophylaxis, including terminal prophylaxis, was not supervised after arrival in the United States, and compliance was reportedly low.

Manifestations of illness included a history of fever and chills (100%), headache (97%), gastrointestinal symptoms (72%), myalgia and/or arthralgia (69%), lumbosacral pain (63%), and upper respiratory symptoms (59%). Patients with falciparum malaria had onset of symptoms an average of 34 days (range: 10-86 days) after return to the United States and 18 days (range: 0-58 days) after discontinuation of prophylaxis; patients with vivax malaria had onset at intervals of 60 days (range: 12-119 days) after return to the United States and 42 days (range: 0-102 days) after discontinuation of prophylaxis. The patients were ill an average of 4 days (range: 0-23 days) before seeking medical attention. In 13 (25%) patients, the diagnosis of malaria was delayed for 3 or more days after initial medical contact.

Reported by: JA Newton, MD, GA Schnepf, MD, CA Kennedy, MD, M O'Hara, MD, M Wallace, MD, CA Ohl, MD, EC Oldfield, MD, Naval Medical Center, San Diego. T Sharp, MD, Naval Medical Research Institute, Bethesda, Maryland. BL Smoak, MD, R DeFraites, MD, AJ Magill, MD, B Wellde, PhD, Walter Reed Army Institute of Research, Washington, DC. S Klamerus, MD, JN Longfield, MD, Health Svcs Command, San Antonio, Texas. Malaria Br, Div of Parasitic Diseases, National Center for Infectious Diseases, CDC.

Editorial Note

Editorial Note: Most U.S. military personnel who developed malaria in Somalia or after their return to the United States had been stationed in the southern riverine area of Somalia, where malaria transmission is intense and is characterized by seasonal exacerbations from May through August and during November and December. Transmission in the central and northern parts of the country is relatively low. P. falciparum is the predominant species of malaria infection among the population and accounts for 94% of malaria cases in Somalia. P. vivax accounts for 4% of cases and P. malariae for 2%; malaria caused by P. ovale occurs rarely (1).

The incubation period for vivax malaria is similar to that for falciparum malaria. Because patients infected with P. vivax became ill several weeks later than those infected with P. falciparum, cases of vivax malaria in military personnel following their return to the United States probably represented relapses of parasitemia from hepatic stages (hypnozoites). Because of the unexpectedly high rate of these relapses, on May 21, the Office of the Surgeon General of the Army mandated primaquine as part of the terminal prophylactic regimen for troops returning from Somalia.

The probability of mosquitoborne transmission of malaria in the United States as a consequence of the return of these military personnel is considered low. From 1966 through 1972, four episodes of transmission in the United States -- resulting in nine cases of malaria -- were identified in association with the 13,843 military personnel subsequently diagnosed with vivax malaria in the United States at the time of their return from Vietnam. Prompt recognition and treatment of malaria is the most important approach for preventing introduction of malaria into the United States.

Malaria must be considered in the differential diagnosis for military personnel and all other persons with fever or a history of fever who have traveled to a malarious area. The diagnosis of malaria initially may not be considered because a complete foreign travel history has not been elicited or because the initial symptoms do not include the classic pattern of repeated episodes of fever and chills and may have a dominant gastrointestinal or respiratory component. For patients who have continued taking prophylaxis or who have recently discontinued prophylaxis, the clinical presentation often is milder than in patients who have not taken any prophylaxis (2,3). Malaria infection can be excluded only after microscopic examination of serial thick and thin blood smears over a 72-hour period. Many of the cases of malaria described in this report were characterized by a low density of parasitemia that was diagnosed only on thick smears.

Physicians should report confirmed cases of malaria to their local health departments and are requested to report confirmed cases to the Office of the Surgeon General of the Army (Col. J.P. Tomlinson, telephone {703} 756-0135) for patients in the U.S. Army, the San Diego Naval Medical Center (LCDR J. Newton, telephone {619} 532-7475) for patients in the U.S. Marines or U.S. Navy, or the Office of the Surgeon General of the Air Force (Col. J. Wright, telephone {202} 767-1835) for patients in the U.S. Air Force.

References

1. World Health Organization. Review of the malaria situation and of research activities carried out on the control of malaria in Somalia. Geneva: World Health Organization, 1984; publication no. WHO/MAL.CT/AFT/5.13.

2. Wetsteyn JCFM, De Geus A. Chloroquine-resistant falciparum malaria imported into the Netherlands. Bull WHO 1985;63:101-8.

3. Lewis SJ, Davidson RN, Ross EJ, Hall AP. Severity of imported falciparum malaria: effect of taking antimalarial prophylaxis. BMJ 1992;305:741-3.

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