[Chloroquine-resistant Plasmodium falciparum malaria confirmed by semi-micro sensitivity test for chloroquine seen in a person returned from Nigeria to Japan].

A 39-year-old Japanese male engineer who stayed in Nigeria from August 17, 1987 through January 22, 1988, presented chloroquine-resistant Plasmodium falciparum malaria. He was taking oral chloroquine prophylactically. But he suffered from P. falciparum malaria in November, 1987 and early January, 1988. He was treated in Nigeria. After his return to Japan, he was admitted to our hospital with a fever of 39 degrees C on January 29, 1988. The peripheral blood smear on admission showed the presence of ring form P. falciparum. He was diagnosed as recrudescence of P. falciparum malaria. Laboratory examination revealed severe thrombocytopenia and biologic false-positive serological tests of syphilis. The level of 50% inhibitory concentration was 0.44 nmol/ml by in vitro chloroquine sensitivity test of the strain of P. falciparum obtained from this patient. Clinically, chloroquine was not effective. The patient was treated with intravenous quinine dihydrochloride followed by sulfadoxine/pyrimethamine tablets and recovered completely. As far as we know through our survey this patient was the first case of chloroquine-resistant P. falciparum malaria brought to Japan from Nigeria.