Results
Incidence of malaria
In each year of the study there were two peaks of malaria
incidence. The first peak coincided with the onset of the
rains in May and June, and the second with the cool
season in November and December. Since 1990 there has
been a gradual decline in the incidence of falciparum
malaria, and a concomitant rise in the incidence of vivax
malaria. From 1990 to mid-1994 the average rate of P
falciparum infection fell from 0,5 to 0,4 infections per
person per year. The mean monthly incidence between
June, 1992, and June, 1994, was 3-37% (SD 1-23) per
month. Then in May to June, 1994, artesunate was
introduced in combination with mefloquine as the
treatment for all cases of falciparum malaria. The
incidence of P falciparum infections fell abruptly, to a
mean of 1-58% (0-74) per month over the following 12
months-a 47% (95% CI 25-69) reduction. By contrast,
there was no reduction in the incidence of P vivax
infections. Anopheline mosquito numbers, which were
being monitored in a concomitant entomological study,
fell greatly in August, 1994, after severe flooding but
returned to normal by November, 1994 (S Lindsay:
personal communication). A flood in 1992 was associated
with only a temporary reduction in the incidence of
falciparum malaria.