PLASMODIAL PREVALENCE RATES AND PARASITIC LOAD IN BLOOD-DONORS IN BRAZZAVILLE, CONGO

To assess the frequency of malaria-infected blood donations in Brazzav ille (Congo) thick films from all blood donors (n=12,375, minimum per month: 857, maximum per month: 1,295; sex ratio: 9.6) at the Brazzavil le University Hospital were examined quantitatively for Plasmodium (sc reening threshold: 20/mu l of blood) over one year (1989). The overall prevalence rate for all species of Plasmodium was 8.5%. It varied acc ording with age but not with sex. P. falciparum predominated (92%), fo llowed by P. malariae (7%) and P. ovale (3%). For P. falciparum : 1 - the prevalence rate was 7.8% but varied over the year from 4.8% in Aug ust (6.2% for the dry season on the whole) to 11.5% in March (9.6% for the rainy season); 2 - the parasitic load, also variable according to the season, was over 600/mu l in 24% of the cases (i.e. 1.9% of all d onations) and over 6,000/mu l in 15 cases (i.e. 1.6% of the cases). In conclusion the proportion of blood donations infected with P. falcipa rum (with a parasitic load greater than or equal to 20/mu l) varied in Brazzaville from 6% in the dry season to 10% in the rainy season.