Human malaria transmission studies in the Anopheles punctulatus complex in Papua New Guinea: sporozoite rates, inoculation rates, and sporozoite densities

Abstract

Malaria sporozoite rates and inoculation rates were measured over periods up to 25 months in the different anopheline species biting humans in 13 villages in Madang Province, Papua New Guinea. Analysis of three members of the Anopheles punctulatus complex, 68,458 An. farauti, 36,779 An. koliensis, and 11,667 An. punctulatus caught in landing catches was made using monoclonal antibody based ELISAs to detect sporozoites of Plasmodium falciparum and P. vivax. Sporozoite rates ranged from 0%-5.5% in An. farauti, 0.2%-3.8% in An. koliensis, and 0%-3.3% in An. punctulatus. In addition, over 3,000 An. longirostris were analyzed and sporozoites were not detected in this species. No significant differences were observed between the three vector species in the densities of P. falciparum sporozoites (geometric mean 2,320). However, the geometric mean P. vivax sporozoite density was significantly higher in An. punctulatus (350) than in either An. koliensis (160) or An. farauti (150). An. koliensis was less susceptible to infections of P. falciparum or P. vivax than either An. farauti or An. punctulatus. Variations in average sporozoite and inoculation rates were found among different villages, despite their close geographic proximity. Sporozoite and inoculation rates varied greatly within a village over time, but malaria transmission was perennial with a higher transmission during the wet season by An. koliensis and An. punctulatus.