Outbreak of Malaria Imported from Kenya

Malaria remains an important problem for U.S. travelers to areas in Africa with chloroquine-resistant Plasmodium falciparum, as illustrated by the following report:

On June 26, 1986, a 29-year-old resident of Louisiana became ill en route to the United States from Nairobi, Kenya. He was admitted to a hospital in Shreveport, Louisiana, with a diagnosis of P. falciparum malaria on June 28. By June 30, seven additional persons with malaria-like symptoms were admitted to three Shreveport hospitals. All patients received medical care within 2 days of the onset of illness; P. falciparum parasites were identified in each patient's blood smears within 2 days after being seen by a physician. All were treated promptly and successfully with quinine and tetracycline.

The eight patients were part of a 10-member church group from Shreveport that had visited Rusinga Island in Lake Victoria in western Kenya June 14-21 and Masai Mara gamepark June 21-23. They had departed for the United States from Nairobi on June 24. All members of the group had taken 500 mg chloroquine weekly as prophylaxis, beginning at least 6 days before their departure for Kenya. Onset of malaria symptoms began 1-6 days after the last chloroquine dose. Analyses of whole-blood specimens obtained when the patients presented at the hospitals documented concentrations of chloroquine (range 75-444 ppb) and desethylchloroquine (range 19-146 ppb), consistent with their prophylaxis histories.

Malaria parasites were not detected in the blood of the two members of the group who did not develop symptoms. One of these persons had been taking 100 mg of tetracycline daily for acne. The remaining uninfected person had reportedly applied insect repellents to exposed areas of the skin more intensively and regularly than had other members of the group. Reported by R Alsup, MD, J Snyder, MD, A Borne, MD, B Williams, MD, Shreveport, J Mathison, MD, State Epidemiologist, Louisiana Dept of Health and Human Resources; Malaria Br, Div of Parasitic Diseases, Center for Infectious Diseases, CDC.

Editorial Note

Editorial Note:Chloroquine-resistant P. falciparum in Kenya and Tanzania was first documented in 1978 (1) and has spread through much of eastern, southern, and central Africa (2). The estimated attack rate of P. falciparum malaria among U.S. travelers returning from Kenya has increased from 21 cases per 100,000 travelers in 1978 to 189/100,000 in 1985. The increased risk of malaria infection for U.S. travelers to Kenya has been attributed to the spread of resistance to chloroquine (3).

The 80% attack rate in the Louisiana group was considerably higher than that experienced by most U.S. travelers to Kenya. Malaria transmission in Kenya was particularly intense in June, following the rainy season in April and May. Also, the highly malarious areas in western Kenya visited by this group are not generally frequented by U.S. tourists.

The infections acquired in this episode resolved favorably because medical care was obtained early; the diagnosis was made quickly; and effective therapy was given promptly. A review of fatal P. falciparum infections among U.S. citizens indicated that lack of prompt and adequate medical care contributed to the fatal outcomes (5).

Although all patients in the Louisiana group had used chemoprophylaxis, and chloroquine may not prevent parasitemia and illness, it does appear to moderate the illness and reduce the risk of fatal P. falciparum infection (5,6). Therefore, it is important that travelers continue to use chloroquine as a prophylactic drug, despite its reduced efficacy to prevent a P. falciparum infection in some countries with chloroquine-resistant strains. Susceptible and resistant strains of P. falciparum often coexist in the same area, and chloroquine remains an effective drug for prophylaxis of malaria caused by P. vivax, P. ovale, and P. malariae.

Current CDC prophylaxis guidelines recommend use of weekly chloroquine for short-term travelers to countries with chloroquine-resistant P. falciparum. In addition, such travelers (except those with histories of sulfonamide intolerance) should also carry one or more treatment doses of Fansidar with them (adult dosage, three tablets as a single dose) to be taken promptly in the event of a febrile illness during their travel when medical care is not readily available. Prophylaxis with weekly Fansidar (in addition to chloroquine) may be considered for travelers who will be at very high risk of infection over a long period without access to medical care. If travelers become ill after their return to the United States, medical care should be sought promptly, and the physician should be informed of the recent travel. Doxycycline alone taken daily during travel and for 6 weeks after leaving the malarious area is an alternative to the regimen indicated above for short-term travel to areas with chloroquine-resistant P. falciparum (adult dose 100 mg daily). It is particularly appropriate for individuals with histories of sulfonamide intolerance (4).

Because of the limited effectiveness of chloroquine prophylaxis in areas with chloroquine-resistant P. falciparum, travelers should be advised to take measures to limit contact with mosquitoes between dusk and dawn. It has been estimated that use of effective personal protective measures can reduce the risk of exposure 10-fold (6). Such measures include: using insect repellents containing N,N diethylmetatoluamide (DEET) on exposed areas of the skin; using pyrethrum-containing flying-insect spray in living and sleeping areas during evening and nighttime hours; using mosquito nets; remaining in well-screened areas; and wearing clothes that cover most of the body during evening and nighttime hours.

Detailed information regarding malaria prophylaxis and other health precautions is provided in the publication, "Health Information for International Travel, 1986" (8)*.

References

1. CDC. Chloroquine-resistant malaria acquired in Kenya and Tanzania--Denmark, Georgia, New York. MMWR 1978;27:463-4.

2. Lobel HO, Campbell CC. Malaria prophylaxis and distribution of drug resistance. In: Strickland GT, ed. Clinics in tropical medicine and communicable diseases. Vol 1, no 1. London: WB Saunders Co, 1986:225-42.

3. CDC. Malaria prevention recommendations. Advisory memorandum no. 88. April 7, 1986.

4. Lobel HO, Campbell CC, Schwartz IK, Roberts JM. Recent trends in the importation of malaria caused by Plasmodium falciparum into the United States from Africa. J Inf Dis 1985;152:613-7.

5. Lobel HO, Campbell CC, Roberts JM. Fatal malaria in US civilians (Letter). Lancet 1985;i:873.

6. Wetsteyn JC, de Geus A. Chloroquine-resistant falciparum malaria imported into the Netherlands. Bull WHO 1985;63:101-8.

7. Peto TEA, Gilks CF. Strategies for the prevention of malaria in travellers: comparison of drug regimens by means of risk-benefit analysis. Lancet 1986;i:1256-60.

8. CDC. Health information for international travel, 1986. Atlanta, Georgia: US Department of Health and Human Services, Public Health Service, 1986. HHS publication no. (CDC) 86-8280. *Available from the U.S. Government Printing Office, Washington, D.C., 20402.

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