Abstract
ObjectiveTo investigate changes in malaria prevalence in Papua New Guinea after the distribution of long-lasting Insecticide-treated nets, starting in 2004, and the introduction of artemisinin-based combination therapy in 2011.MethodsTwo malaria surveys were conducted in 2010–2011 and 2013–2014. They included 77 and 92 randomly selected villages, respectively. In each village, all members of 30 randomly selected households gave blood samples and were assessed for malaria infection by light microscopy. In addition, data were obtained from a malaria survey performed in 2008–2009.ResultsThe prevalence of malaria below 1600 m in altitude decreased from 11.1% (95% confidence interval, CI: 8.5–14.3) in 2008–2009 to 5.1% (95% CI 3.6–7.4) in 2010–2011 and 0.9% (95% CI 0.6–1.5) in 2013–2014. Prevalence decreased with altitude. Plasmodium falciparum was more common than P. vivax overall, but not everywhere, and initially the prevalence of P. vivax infection decreased more slowly than P. falciparum infection. Malaria infections were clustered in households. In contrast to findings in 2008–2009, no significant association between net use and prevalence was found in the later two surveys. The prevalence of both fever and splenomegaly also decreased but their association with malaria infection became stronger.ConclusionLarge-scale insecticide-treated net distribution was associated with an unprecedented decline in malaria prevalence throughout Papua New Guinea, including epidemic-prone highland areas. The decline was accompanied by broader health benefits, such as decreased morbidity. Better clinical management of nonmalarial fever and research into residual malaria transmission are required.
Highlights
Malaria has been endemic throughout Papua New Guinea, except in highland areas over 1600 m, where temperatures are low and there is no stable local transmission, though imported cases and epidemics do occur.[1,2,3] The causative parasites Plasmodium falciparum, Plasmodium vivax, Plasmodium malariae and Plasmodium ovale are transmitted by various Anopheles mosquito species adapted to distinct ecological niches.[4]
Light microscopy diagnosis indicated that P. falciparum was the most common species, followed by P. vivax, which dominated in several locations
The first survey in 2008–2009, whose results are presented for comparison, included villages from only districts covered by the long-lasting insecticide-treated net campaign, but the method of selecting households and their members was identical to that in subsequent surveys.[7]
Summary
Malaria has been endemic throughout Papua New Guinea, except in highland areas over 1600 m, where temperatures are low and there is no stable local transmission, though imported cases and epidemics do occur.[1,2,3] The causative parasites Plasmodium falciparum, Plasmodium vivax, Plasmodium malariae and Plasmodium ovale are transmitted by various Anopheles mosquito species adapted to distinct ecological niches.[4]. In 2008–2009, towards the end of the first insecticidetreated net campaign, the Papua New Guinean Institute of Medical Research conducted a country-wide malaria indicator survey. It documented that 65% of households in areas covered by the campaign owned long-lasting insecticide-treated nets and that 33% of people were using them.[5] In addition, malaria was found to be widespread, with a heterogeneous prevalence.[7] Light microscopy diagnosis indicated that P. falciparum was the most common species, followed by P. vivax, which dominated in several locations. Entomological investigations indicated that biting patterns and changes in these patterns may reduce the impact of vector control.[9]
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