Non-immune patients in the Democratic Republic of São Tomé e Principe reveal a high level of transmission of P. ovale and P. vivax despite low frequency in immune patients

Malaria parasite species circulating in immune inhabitants of the Democratic Republic of São Tomé e Principe (DRSTP) and those acquired by non-immune travellers returning from this country have been compared. Using sensitive detection and species identification by PCR, Plasmodium parasites were found in the blood of 16 of the 43 travellers, who reported during the first 8 months of 1995 to a clinical diagnosis laboratory in Lisbon. Plasmodium vivax was found in four (25%) and Plasmodium ovale in ten (63%) of these patients. The observed prevalence of these two species in infected patients of DRSTP during 1995/1996 was <2%.