Malaria in Montagnard Refugees -- North Carolina, 1992

Refugee groups emigrating from some areas of the world may have increased prevalences of exotic and potentially life-threatening diseases, challenging the diagnostic and case-management capacities of local and state health departments. This report summarizes efforts by public health officials and clinical health-care providers to diagnose and manage cases of malaria among a group of 402 Montagnard refugees who resettled to three counties in North Carolina in November 1992.

Since 1976, this group of Montagnard refugees has lived in a remote, densely forested area along the Cambodian-Vietnamese border where transmission of Plasmodium vivax and multidrug-resistant P. falciparum is intense. Before immigrating to the United States, the Montagnards spent 1 month in Phnom Penh, Cambodia, where they received routine physical examinations and screenings for human immunodeficiency virus, syphilis, tuberculosis, and other excludable physical and mental conditions. Of the 402 persons in this group, 299 (74%) were male, and 80 (20%) were children aged less than 10 years. Members of the group were resettled in Guilford County (175), Mecklenburg County (159), and Wake County (68). Within 1 month of arrival, one Montagnard died (from empyema and gram-negative sepsis), 16 were hospitalized, and 36 had illnesses requiring emergency medical assessment. Five cases of malarial illness were reported among members of the group in one county.

Because an initial assessment among 20 persons detected a 35% prevalence of parasitemia with either P. falciparum or P. vivax, all Montagnards were screened using quantitative buffy coat (QBC*) evaluation followed by thick and thin blood-smear examination. Self-reported history of fever was recorded at the time of blood collection to determine the association between fever and parasitemia among this group.

Of the 376 persons for whom QBC and/or thick-smear results were available, 178 (47%) were infected with one or more species of Plasmodium; 25 persons had been treated previously or were unavailable for screening. Among infected persons, 93 (52%) had P. falciparum, 71 (40%) had P. vivax, and five (3%) had P. malariae; 35 (20%) had Plasmodium parasites of unknown species. Infections with more than one species of Plasmodium were documented in 39 (22%) parasitemic persons. Among 161 persons with slide-positive malaria for whom a fever history was recorded, 27 (17%) reported having fever since arriving in the United States, suggesting a high level of acquired immunity to malarial illness among this group.

Because of the high prevalence of asymptomatic infection, all 402 members of the group were treated with halofantrine (Halfan*). Halofantrine was administered because P. falciparum strains from Southeast Asia are commonly resistant to other available antimalarials, including partial resistance to quinine. Halofantrine is highly effective against the blood stage of malaria parasites but has no effect on the liver stage of P. vivax (hypnozoites), which can produce malaria relapses for 3-5 years after initial infection. The risk for P. vivax relapse can be decreased by treating infected persons with primaquine (the only available antimalarial that is active against hypnozoites); however, because primaquine can cause severe hemolytic anemia in patients deficient in the red blood cell enzyme glucose-6-phosphate dehydrogenase (G6PD), all refugees for whom primaquine was indicated were screened for G6PD deficiency. Of 358 persons screened, 11 (3%) had G6PD deficiency of sufficient severity to preclude the use of primaquine.

After treatment, group sessions were held to inform the Montagnards, community leaders, and the staff of the sponsoring agencies about the risk for malaria relapse and the importance of early diagnosis and treatment. In addition, guidelines for the proper diagnosis and treatment of malaria were disseminated to selected health-care providers.

Reported by: S Sommer, MD, D Burtt, Guilford County Health Dept, Greensboro; S Keener, MD, Mecklenburg County Health Dept, M Pierce, Catholic Social Svcs, Charlotte; P Morris, MD, B McIntyre, Wake County Dept of Health, J Neff, Wake Health Svcs, Raleigh; JM Robertson, MD, Dept of Social Medicine, Univ of North Carolina, Chapel Hill; R Meriwether, MD, Communicable Disease Control, L Turner, PhD, JN MacCormack, MD, State Epidemiologist, Div of Health Svcs, North Carolina Dept of Environment, Health, and Natural Resources. Div of Quarantine, National Center for Prevention Svcs; Malaria Br, Div of Parasitic Diseases, National Center for Infectious Diseases, CDC.

Editorial Note

Editorial Note: The resettlement of the Montagnard refugees within 2 months of leaving an area of intense malaria transmission, without screening or presumptive treatment for malaria parasitemia, resulted in higher levels of malaria infection than previously seen in Southeast Asian refugees on arrival to the United States. This high prevalence might have been anticipated, because 25%-49% of persons entering Thai refugee camps from forested regions of Cambodia in the early 1980s were parasitemic (1,2). Unlike the Montagnards, these refugees typically remained in temporary resettlement camps in Asia for 4-5 months before arrival in the United States. Although the primary purpose of these camps was to provide cultural information and language training before immigration, this period also provided an opportunity to detect and treat malaria and other medical conditions. As a result, in 1980, among 3433 Indochinese (Laotian, Cambodian, and Vietnamese) refugees resettled in the United States, the prevalence of parasitemia was less than 2% (3).

Malaria was one of many health problems among these refugees; however, requirements for diagnosis, treatment, and management of malaria exceeded the capacity of the local and state health departments, many of which are neither staffed nor funded to provide primary health care. County health departments estimated that as long as 14 weeks would be needed to complete initial medical screening of the refugees, and the capacity of the state laboratory was exceeded by the need to rapidly process nearly 40 times the annual expected number of malaria slides. Even with technical assistance from CDC, malaria-specific screening and treatment procedures required 8 weeks for completion.

Although mosquitoes capable of transmitting malaria exist in North Carolina, local transmission of malaria is unlikely for at least three reasons. First, these Montagnard refugees arrived in November, when temperatures were low enough to preclude survival of anopheline mosquitoes. Second, when warmer ambient temperatures enable increases in the mosquito population, the housing conditions (including the presence of window screens) for persons in this group substantially decrease the likelihood that parasitemic persons will be exposed to anopheline mosquitoes. In recent periods, local transmission in the United States has occurred only when large groups of infected persons have resided outdoors or in substandard housing (e.g., migrant workers encamped in southern California {4}). Finally, any theoretical risk of local transmission in this setting will be further diminished by the presumptive treatment of all members of the resettled group, ongoing case detection and treatment of relapses, and administration of antimalarials to prevent relapses.

Expertise for prompt and accurate diagnosis of malaria and other exotic but potentially life-threatening medical problems in a large number of persons is limited in most local and state health departments (5). As a result, laboratory services and personnel can be quickly overwhelmed. Refugees who immigrate to the United States from tropical areas, among whom prevalences of malaria or other infectious diseases may be high, should receive medical screening and appropriate treatment under well-controlled conditions before departing for the United States. When this is not possible, medical personnel, laboratory support services, and other resources should be made available to local and state health departments to ensure adequate and timely health care.

References

1. Glass RI, Nieburg P, Cates W Jr, et al. Rapid assessment of health status and preventive-medicine needs of newly arrived Kampuchean refugees -- Sakaeo, Thailand. Lancet 1980; 1:868-72.

2. CDC. Health status of Kampuchean refugees -- Khao I-Dang. MMWR 1979;28:569-70.

3. Guerrero IC, Chin W, Collins WE. A survey of malaria in Indochinese refugees arriving in the United States, 1980. Am J Trop Med Hyg 1982;31:897-901.

4. Maldonado YA, Nahlen BL, Roberto RR, et al. Transmission of Plasmodium vivax malaria in San Diego County, California, 1986. Am J Trop Med Hyg 1990;42:3-9.

5. Lederberg J, Shope RE, Oaks SC, eds. Institute of Medicine. Emerging infections: microbial threats to health in the U.S. Washington, DC: National Academy Press, 1992:137.

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