AN EPIDEMIC OF PLASMODIUM-FALCIPARUM MALARIA IN BALCAD, SOMALIA, AND ITS CAUSATION

The causative factors of an epidemic of falciparum malaria were invest igated in Balcad, Somalia, a town with previously low malaria transmis sion, where malaria incidence rose more than twenty-fold between 1986 and 1988, The emergence of chloroquine resistance, accelerated by high drug pressure, low herd immunity and favourable meteorological condit ions were identified as major causes of the epidemic. Chloroquine resi stance of grades RII and RIII was first observed in Balcad in 1987 and rapidly increased to 72% of the Plasmodium falciparum infections in 1 988. In the absence of alternative treatment, resistance resulted in t he accumulation of a massive infective reservoir and therefore increas ed malaria transmission, associated with intensive clinical symptomato logy. The advent of chloroquine resistance was less violent in the are a of Malable, where malaria is stable and communal immunity higher tha n in Balcad.