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East Afr Med J. 1991 Aug;68(8):606-10.

Sensitivity of falciparum malaria to chloroquine and amodiaquine in four districts of western Kenya (1985-1987).

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Centre for Vector Biology and Control, Kisumu, Kenya.


In-vivo and in-vitro studies to determine the sensitivity of Plasmodium falciparum malaria to chloroquine and amodiaquine were conducted in 4 districts of Western Kenya over a 2-year-period. Patients aged 5-60 years, were treated with chloroquine or amodiaquine base 25 mg/kg over 3 days. Recurrence of parasitaemia within 7 days (R1 resistance) or failure to clear parasites (R11 resistance) was observed in 27% of infections in West Pokot district, 51% in Busia, 45% in Bungoma and 19% in Rusinga Island. R111 resistance (failure to decrease parasitaemia by at least 75%) was documented in Rusinga Island. The proportions of parasites with minimum inhibitory concentrations (MICs) for chloroquine greater than 114 nM in in-vitro tests ranged from 37% in Busia to 68% in Bungoma. For amodiaquine, 20% of 30 isolates tested had MICs greater than 80 nM. We conclude that resistance to chloroquine is now established in the area and amodiaquine may be useful in uncomplicated chloroquine resistant falciparum infections in the region.


Between 1985-1987, researchers recruited 419 5-60 year old persons with moderate falciparum malaria to take part in a series of studies in West Pokot, Rusinga Island, Busia, and Bungoma districts in western Kenya to determine malaria parasite sensitivity to chloroquine and amodiaquine. The subject received 25mg/kg of the antimalarial for 3 days. Chloroquine resistance was highest in Busia in May 1986 (51%) followed by Bungoma (45%), Busia in July 1986 (38%), West Pokot (27%), and Rusinga Island (19%). No RIII resistance (failure to decrease parasitemia by at least 75%) occurred in any of the 4 studies. In July 1986, researchers compared the different sensitivity levels of chloroquine and amodiaquine among 119 school children in Busia. None of the children exhibited RIII resistance. None of the falciparum malaria parasites in the 58 children receiving amodiaquine showed RII resistance (failure to clear parasites) compared to 3.3% of those receiving chloroquine. Yet 15.5% of students receiving amodiaquine harbored parasites with RI resistance (recurrence of parasitemia within 7 days), especially delayed RI resistance. Still this percentage was much lower than RI resistance among the students receiving chloroquine (34.4%). Total resistance was significantly much higher in the chloroquine group than the amodiaquine group (p.01). Moreover in vitro studies revealed that the percentages of parasites with minimum inhibitory concentrations (MICs) for chloroquine 114 nM (indicating resistance) varied from 37% in Busia to 68% in Bungoma. Further 20% had MICs for amodiaquine 80 mM (indicating resistance). In conclusion, chloroquine resistant falciparum malaria parasites have established themselves in western Kenya. Despite growing resistance, amodiaquine should still be used in uncomplicated infections, if the health practitioner is able to follow up on the patients.

[Indexed for MEDLINE]

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