A clonal Plasmodium falciparum population in an isolated outbreak of malaria in the Republic of Cabo Verde

We present the first parasitological, molecular and longitudinal analysis o f an isolated outbreak of malaria. This outbreak occurred on Santiago Islan d (Republic of Cabo Verde), a region where malaria is hypoendemic and contr olled, and thus the population is considered non-immune. Blood samples were collected from the inhabitants over 1 month and during cross-sectional sur veys in the following year. The presence and nature of the parasites was de termined by PCR. Plasmodium falciparum was the only species detected. Genet ic analysis revealed that the circulating parasites were genetically homoge neous, and probably clonal. Gametocytes were found throughout this period. Our data suggest that this represented a focal outbreak, resulting in the i nfection of at least 40 % of the villagers with a clonal parasite line. Thu s, P. falciparum infections can persist for at least 1 year in a substantia l proportion (10 %,) of the hosts. Implications for malaria control and the interpretation of epidemiological data are discussed.