Status of chloroquine efficacy against falciparum malaria in the Mola area of Kariba district, Zimbabwe

The therapeutic efficacy of chloroquine was assessed, during the 1997 transmission season, using 64 cases of uncomplicated, falciparum malaria originating from 18 villages in the Mola area of Kariba district, Zimbabwe. Chloroquine effected a modest reduction in asexual parasite density and clinical symptoms. The mean density of asexual parasites on day 3 post-treatment was 24.94% (95% confidence interval = 13.59%-36.30%) of that on day 0, and 78% of the patients followed-up for at least 1 week were free of parasitaemia on day 7. However, there was appreciable therapeutic failure. The early treatment failure rate (i.e. by day 3) was 21% and about 6% of the cases exhibited increasing asexual parasitaemia despite treatment. Late treatment failures (i.e. by day 14) occurred in 32% of the malaria cases, and 52% of the patients were ultimately considered failures. All the failures were successfully treated with sulfadoxine-pyrimethamine or quinine. Chloroquine therefore has declining parasitological and clinical value as the first-line, presumptive treatment for uncomplicated, falciparum malaria in the study area, necessitating strategies to cope with resistant cases. The proportion of the patients failing to be treated successfully with chloroquine, one of the largest reported in Zimbabwe to date, may force major policy reviews in the near future. It is recommended that the second-line antimalarial, sulfadokine-pyrimethamine, be distributed to health-centre level in the study area, backed up by the decentralised confirmation of diagnosis. Measures to deal with treatment failures at local health centres are proposed.