The sensitivity of Plasmodium falciparum to chloroquine was tested in Muheza, Pangani, Tanga and Korogwe districts in north-eastern Tanzania by applying both in vivo and in vitro tests in schoolchildren. A total dose of 25 mg chloroquine base/kg body-weight given over a period of three days (10 mg/kg on days 0 and one; and 5 mg/kg on day 2) failed to clear asexual parasites from the peripheral blood by day 7 in 12.5% of the children tested at Muheza, 5.9% at Pangani, 31.8% at Tanga, and 39.5% at Korogwe. In vitro micro tests were successfully carried out on 44 isolates at Muheza, 29 isolates at Pangani, 45 isolates at Tanga and 44 isolates at Korogwe. Schizont maturation at chloroquine concentrations of 1.14 mu mol/litre of blood and above, an indication of drug resistance, was observed in 20.5% of the isolates at Muheza, 41.4% at Pangani, 51.1% at Tanga and 45.5% at Korogwe. In vivo and in vitro results of the tests for resistance have been compared.
The sensitivity of Plasmodium falciparum strains to Fansidar (500 mg sulphadoxine/25 mg pyrimethamine) was tested in vivo in six localities in the United Republic of Tanzania where chloroquine-resistant P. falciparum strains have been demonstrated by both in vivo and in vitro tests. Single doses as recommended by the manufacturers achieved 100% clearance of parasitaemia in five localities with mean clearance period of between 2.2 and 2.9 days. In one locality (Gonja) the recommended dose failed to clear parasitaemia in two of the 38 cases (5.3%) within seven days. The possibility of using this drug combination for the treatment of chloroquine-resistant P. falciparum strains in the United Republic of Tanzania is discussed.
Various immunoassays have been introduced into, and evaluated at, the Amani Medical Centre in north-east Tanzania. These include immunoblotting to identify mosquito bloodmeals, immunoradiometric and immunoenzymatic assays to assess the presence of circumsporozoite protein in mosquitoes, and enzyme-linked immunosorbent assays to measure antibodies to circumsporozoite antibody in people. The assays were shown to be reliable and practicable for use in the study of malaria epidemiology.
Studies were undertaken in the towns of Muheza, Korogwe and Tanga in Tanga region, north-eastern Tanzania in 1986 to assess the sensitivity of Plasmodium falciparum to mefloquine using an in vitro microtechnique. Successful tests were achieved on 29, 40 and 118 isolates from Korogwe, Muheza and Tanga respectively. The mean minimum inhibitory concentrations (logometric) were 0.52, 0.50 and 0.59 mumol per litre of blood for Korogwe, Muheza and Tanga respectively. Six isolates, 2 from Muheza and 4 from Tanga, showed resistance to mefloquine, having minimum inhibitory concentrations greater than 3.2 mumol per litre of blood. The chloroquine and mefloquine sensitivities of the isolates which showed mefloquine resistance were determined.
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