[Plasmodium prevalence and parasitic burden in blood donors of Brazzaville, Congo].

To assess the frequency of malaria-infected blood donations in Brazzaville (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 Brazzaville University Hospital were examined quantitatively for Plasmodium (screening threshold: 20/microliters of blood) over one year (1989). The overall prevalence rate for all species of Plasmodium was 8.5%. It varied according with age but not with sex. P. falciparum predominated (92%), followed 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 August (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/microliters in 24% of the cases (i.e. 1.9% of all donations) and over 6,000/microliters in 15 cases (i.e. 1.6% of the cases). In conclusion the proportion of blood donations infected with P. falciparum (with a parasitic load > or = 20/microliters) varied in Brazzaville from 6% in the dry season to 10% in the rainy season.