Area effects of bednet use in a malaria-endemic area in Papua New Guinea

Abstract

Relationships between area coverage with insecticide-free bednets and prevalence of Plusvv~udiumfalcipanrm were investigated in 7 community-based surveys over a 33-month period in 1990-93 in 6 villages in the Wosera area of Papua New Guinea. Spatial patterns in circumsporozoite rates for I? jalciparum, I? oivax isomorphs K210 and K247, and i? mah-iae, and the proportions of mosquito blood meals positive for specific human, goat, cat, dog and pig antigens were determined using ELISAs. I? fakiparulm prevalence in humans was better explained by bednet coverage in the immediate vicinity than by personal protection alone. Circumsporozoite rates for both P jalci@rum and I? &ax were also inversely related to coverage with bednets. There was some increase in zoophagy in areas with high coverage, but relatively little effect on the human blood index or on overall mosquito densities. In this setting, protracted use ofuntreated bednets apparently reduces sporozoite rates, and the associated effects on prevalence are greater than can be accounted for by personal protection. Even at high bednet coverage most anophe1ines feed on human hosts, so the decreased sporozoite rates are likely to be largely due to reduction of mosquito survival. This finding highlights the importance of local vector ecology for outcomes of bednet programmes and suggests that area effects ofuntreated bednets should be reassessed in other settings,

Prospective risk of morbidity in relation to malaria infection in an area of high endemicity of multiple species of Plasmodium.

“…19 Plasmodium falciparum was observed in 3,959 samples (39.6%), P. vivax in 1,826 (18.3%), and P. malariae in 1,380 (13.8%). Co-infections of both P. vivax and P. malariae with P. falciparum were detected at almost exactly the frequencies predicted if the different species occurred independently (Table 1).…”

High Levels of Genetic Diversity of Plasmodium falciparum Populations in Papua New Guinea despite Variable Infection Prevalence

“…22 and multiple clones observed in 40-50% of infections. 2,23 Although traditionally considered holoendemic, 24,25 more recently malaria transmission in the Wosera region of the East Sepik Province has dropped, ranging between 0.15 and 0.7 infective bites/person/night [26][27][28] with an infection prevalence of 19.5-23.9% 29 and multiple infections are observed in 26% of infections, 29 below that observed in many other parts of Madang and East Sepik Province. 15 The study sites in Madang included 12 villages distributed among three catchment areas-Mugil: comprising Matukar, Bunu, Karkum, and Dimer; Malala: comprising Wakorma, Malala, Suraten, Amiten, and Susure; and Utu: comprising three villages around the region around the village of Utu Sub-Health Center.…”

Geographical Structure of Diversity and Differences between Symptomatic and Asymptomatic Infections for Plasmodium falciparum Vaccine Candidate AMA1

“…The Wosera region (Eastern Sepik Province, Papua New Guinea) is an area of year-round high transmission of P. falciparum malaria, and P. vivax and P. malariae are also common there (19,20). Transmission occurs mainly through members of the Anopheles punctulatus complex, and the number of P. falciparum infective bites per year is around 100 (23,24).…”