Malaria in Sao Tome and Principe: parasite prevalences and vector densities

A cross-sectional survey was carried out in 16 localities on the island of Sao Tome and three on the island of Principe, at the end of the rainy seaso n of 1997, to determine malaria prevalence and vector densities. Blood samp les from 664 inhabitants of all ages were examined by optical microscopy (O M) and PCR. Mosquito collections were made by outdoor landing captures from 21:00-23:00 h. Great differences were found between OM and PCR readings. O M had a sensitivity of 66%, a specificity of 79% and failed to reveal any m ixed-infections. Overall prevalence, determined by PCR, was higher in Sao T ome (53%) than in Principe (35%). It was highest in children below 16 years -old. All four human Plasmodium species occurred in Sao Tome but P. ovale w as not detected in Principe; The human population was largely asymptomatic. Bednet users had lower prevalence than did non-users. The FOREST form of A nopheles gambiae s.s., identified by PCR and cytogenetics, was the only vec tor on the islands. The sporozoite rate in Sao Tomb, assessed by ELISA, was 0.5%. Parasite prevalence and vector densities were positively correlated in Sao Tome. where malaria transmission must occur predominantly in the mor e populated coastal areas. (C) 2000 Elsevier Science B.V. All rights reserv ed.