Cross-sectional characterization of malaria in Sanma and Shefa Provinces, Republic of Vanuatu: malaria control implications.

Endemic malaria still exists in the Republic of Vanuatu, an 80-island archipelago that sits astride the southeast margin of the Southeast Asian-Melanesian malaria band (Buxton Line 170 degrees E, 20 degrees S). The annual parasite incidence has decreased dramatically over the past decade, which has been attributed to an intensive insecticide-treated bednet distribution program and implementation of a revised Plasmodium falciparum treatment policy that employs combination chloroquine + sulfadoxinelpyrimethamine as a first-line therapy. Standard malariometric surveys were conducted at 10 locations in 2 provinces, screening 2351 adults and children towards the end of the peak transmission season. Spleen rates were consistent with mesoendemic malaria. Examination of blood slides revealed a mean slide-positive rate of 22% (range 4% to 33%). P. falciparum predominated, accounting for 73% of infections, followed by P. vivax (25%). Among 396 individuals with P. falciparum, the gametocyte rate was 54%, with 37% presenting gametocytes alone without asexual stages. Only 8% and 4% of persons with asexual stage P. falciparum and P. vivax parasitaemia, respectively, were symptomatic. These data suggest that malaria transmission has increased in some locations in Vanuatu over the past decade and this report underscores the importance of appropriate bednet use and vector control in this setting as well as the impact of adding sulfadoxine/pyrimethamine and removing primaquine from the national malaria treatment formulary.