Abstract
BackgroundThe major malaria vectors of Papua New Guinea exhibit heterogeneities in distribution, biting behaviour and malaria infection levels. Long-lasting, insecticide-treated nets (LLINs), distributed as part of the National Malaria Control Programme, are the primary intervention targeting malaria transmission. This study evaluated the impact of LLINs on anopheline density, species composition, feeding behaviour, and malaria transmission.MethodsMosquitoes were collected by human landing catch in 11 villages from East Sepik Province and Madang Province. Mosquitoes were collected for 3 years (1 year before distribution and 2 years after), and assayed to determine mosquito species and Plasmodium spp. infection prevalence. The influence of weather conditions and the presence of people and animals on biting density was determined. Determinants of biting density and sporozoite prevalence were analysed by generalized estimating equations (GEE).ResultsMosquito biting rates and entomological inoculation rates decreased significantly after the distribution. Plasmodium falciparum and P. vivax sporozoite prevalence decreased in year 2, but increased in year 3, suggesting the likelihood of resurgence in transmission if low biting rates are not maintained. An earlier shift in the median biting time of Anopheles punctulatus and An. farauti s.s. was observed. However, this was not accompanied by an increase in the proportion of infective bites occurring before 2200 hours. A change in species composition was observed, which resulted in dominance of An. punctulatus in Dreikikir region, but a decrease in An. punctulatus in the Madang region. When controlling for village and study year, An. farauti s.s., An. koliensis and An. punctulatus were equally likely to carry P. vivax sporozoites. However, An. punctulatus was significantly more likely than An. farauti s.s. (OR 0.14; p = 0.007) or An. koliensis (OR 0.27; p < 0.001) to carry P. falciparum sporozoites.ConclusionsLLINs had a significant impact on malaria transmission, despite exophagic and crepuscular feeding behaviours of dominant vectors. Changes in species composition and feeding behaviour were observed, but their epidemiological significance will depend on their durability over time.Electronic supplementary materialThe online version of this article (doi:10.1186/s12936-015-1067-7) contains supplementary material, which is available to authorized users.
Highlights
The major malaria vectors of Papua New Guinea exhibit heterogeneities in distribution, biting behaviour and malaria infection levels
In both Madang sites, biting densities peaked in September 2008 and generally declined until LLINs were distributed in August 2009
This study has demonstrated a strong community impact of LLINs on exophagic and early biting vector populations
Summary
The major malaria vectors of Papua New Guinea exhibit heterogeneities in distribution, biting behaviour and malaria infection levels. Malaria transmission in Papua New Guinea (PNG) is highly variable across environmentally diverse zones, Reimer et al Malar J (2016) 15:25 ivax, P. ovale, and P. malariae) with the majority of infections caused by P. falciparum and P. vivax [3, 4]. The major malaria and filariasis vectors in PNG are members of the Anopheles punctulatus group. This group comprises 13 species, each exhibiting different degrees of exophily and anthropophily and different habitat preferences [5,6,7,8]. The five major malaria vectors in this group, due to their widespread distribution and high abundance, include An. punctulatus, An. farauti s.s., An. koliensis, An. hinesorum, and An. farauti 4 [5]. Morphological identification, based on proboscis scale patterns and the presence of a sector spot on the costal wing vein, was often unreliable in distinguishing An. koliensis due to variable scaling patterns, even within isofemale lines [12,13,14,15]
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