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Epidemiologic Notes and Reports Chloroquine-Resistant Plasmodium falciparum Malaria in West Africa

On May 27, 1986, a 50-year-old American helicopter mechanic traveled to Enugu, a city in the eastern state of Anambra, Nigeria. While in Nigeria, he took chloroquine 300 mg base weekly for malaria chemoprophylaxis and continued this regimen after returning to the United States via Lagos on December 6. He traveled only in eastern Nigeria and did not travel to other malarious countries. On December 9, he developed fever, chills, and headache, and was hospitalized in California on December 18.

On December 20, a peripheral blood smear revealed that 0.5% of red blood cells were infected with asexual Plasmodium falciparum parasites, and treatment with chloroquine 1500 mg base was administered over a 3-day period. He became afebrile on December 22, and a peripheral blood smear on December 23 showed rare trophozoites. On December 27, he again became febrile, and a blood smear on December 31 revealed a parasitemia of 1.0%. A whole-blood specimen collected on December 31 was analyzed by high performance liquid chromatography (1) and contained 151 ng of chloroquine/ml, indicating that the treatment dosage of chloroquine had been adequately absorbed.

A parasite isolate collected on December 31 was assayed by the 48-hour in vitro test of Nguyen-Dinh and Trager (2) and found to be resistant to chloroquine: parasite multiplication was inhibited only at 0.3 umol of chloroquine liter of medium, a concentration higher than the accepted limit of in vitro chloroquine resistance (0.06 umol/L). The patient responded promptly to treatment with quinine (650 mg three times daily for 3 days) and tetracycline (250 mg four times daily for 7 days) and has remained well. Reported by DV Jackson, MD, P Marcarelli, MD, G Segal, MD, Dept of Infectious Diseases, Long Beach Veterans Administration/University of California, Irvine, SW Waterman, MD, County of Los Angeles Dept of Health Svcs, RR Roberto, MD, California Dept of Health Svcs; Control Technology Br, Malaria Br, Div of Parasitic Diseases, Center for Infectious Diseases, CDC.

Editorial Note

Editorial Note: Chloroquine-resistant P. falciparum was first confirmed in Africa in 1979 when a P. falciparum infection in a traveler returning from Tanzania was not cured by a standard treatment regimen of chloroquine, and the infecting parasite was found to be resistant to chloroquine in vitro (3). Subsequently, chloroquine-resistant P. falciparum has spread throughout East and Central Africa and, in 1985, was reported from as far west as Cameroon (4). A recent report from Benin (5) and the case from Nigeria presented here indicate that chloroquine-resistant P. falciparum is now present in West Africa as well.

These reports of chloroquine-resistant P. falciparum malaria have serious public health implications since malaria transmission in much of West Africa is intense and perennial. In Nigeria, the most populous nation on the African continent, a change in the efficacy of chloroquine, the most widely used anti-malarial drug, could affect many of the country's estimated 80-100 million residents. Since chloroquine-resistance can extend rapidly after it is first observed in a geographic region, the efficacy of chloroquine will need to be systematically monitored by health care personnel throughout West Africa.

In accordance with Centers for Disease Control (CDC) recommendations for short-term travelers to chloroquine-resistant areas, travelers to Nigeria and Benin should take weekly chloroquine prophylaxis and should also carry pyrimethamine sulfadoxine (FansidarR) to be taken in the event of a fever or flu-like illness when medical attention is not readily available (6). Additionally, since P. falciparum infections that are chloroquine prophylaxis failures may respond poorly to full treatment dosages of chloroquine (7), they should be treated with anti-malarial medications that are effective against chloroquine-resistant infections.

The Malaria Branch CDC is currently assisting in the investigation of additional cases of possible chloroquine-resistant P. falciparum malaria acquired elsewhere in West Africa. CDC will update malaria prophylaxis recommendations as further information regarding the geographic extent of chloroquine-resistant P. falciparum becomes available. Physicians treating patients with P. falciparum infections that were acquired in West Africa and that may represent chloroquine prophylaxis or treatment failures are encouraged to report these cases promptly to their local or state health departments and to the Malaria Branch CDC (telephone: weekdays (404)452-4046, nights and weekends (404)329-2888).


  1. Patchen LC, Mount DL, Schwartz IK, Churchill FC. Analysis of filter-paper-absorbed, finger-stick blood samples for chloroquine and its major metabolite using high-performance liquid chromatography with fluorescence detection. J Chromatography 1983;278:81-9.

  2. Nguyen-Dinh P, Trager W. Plasmodium falciparum in vitro: determination of chloroquine sensitivity of three new strains by a modified 48-hour test. Am J Trop Med Hyg 1980;29:339-42.

  3. Campbell CC, Chin W, Collins WE, Teutsch SM, Moss DM. Chloroquine-resistant Plasmodium falciparum from East Africa: cultivation and drug sensitivity of the Tanzanian I/CDC strain from an American tourist. Lancet 1979;ii:1151-4.

  4. Sansonetti PJ, Lebras C, Verdier F, Charmot G, Dupont B, Lapresle C. Chloroquine-resistant Plasmodium falciparum in Cameroon (Letter). Lancet 1985;i:1154-5.

  5. Le Bras J, Hatin I, Bouree P, et al. Chloroquine-resistant falciparum malaria in Benin. Lancet 1986;ii:1043-4.

  6. CDC. Health information for international travel, 1986. Atlanta, Georgia: Public Health Service, 1986. DHHS publication no. (CDC) 86-8280.

  7. Weniger BG, Blumberg RS, Campbell CC, Jones TC, Mount DL, Friedman SM. High-level chloroquine resistance of Plasmodium falciparum malaria acquired in Kenya. New Engl J Med 1982;307:1560-2.

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