Insecticide-treated nets and malaria prevalence, Papua New Guinea, 2008–2014

Abstract Background Long-lasting insecticidal nets (LLIN), improved diagnosis and artemisinin-based combination therapy (ACT) have reduced malaria prevalence in Papua New Guinea since 2008. Yet, national incidence trends are inconclusive due to confounding effects of the scale-up of rapid diagnostic tests, and inconsistencies in routine reporting. Methods Malaria trends and their association with LLIN and ACT roll-out between 2010 and 2014 in seven sentinel health facilities were analysed. The analysis included 35,329 fever patients. Intervention effects were estimated using regression models. Results Malaria incidence initially ranged from 20 to 115/1000 population; subsequent trends varied by site. Overall, LLIN distributions had a cumulative effect, reducing the number of malaria cases with each round (incidence rate ratio ranging from 0.12 to 0.53 in five sites). No significant reduction was associated with ACT introduction. Plasmodium falciparum remained the dominant parasite in all sentinel health facilities. Resurgence occurred in one site in which a shift to early and outdoor biting of anophelines had previously been documented. Conclusions LLINs, but not ACT, were associated with reductions of malaria cases in a range of settings, but sustainability of the gains appear to depend on local factors. Malaria programmes covering diverse transmission settings such as Papua New Guinea must consider local heterogeneity when choosing interventions and ensure continuous monitoring of trends.

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Investigating differences in village-level heterogeneity of malaria infection and household risk factors in Papua New Guinea

Scientific Reports ◽

10.1038/s41598-021-95959-8 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Desmond Gul ◽

Daniela Rodríguez-Rodríguez ◽

Elma Nate ◽

Alma Auwan ◽

Mary Salib ◽

...

Keyword(s):

Risk Factors ◽

Spatial Heterogeneity ◽

Papua New Guinea ◽

New Guinea ◽

Malaria Prevalence ◽

Malaria Risk ◽

Cross Sectional ◽

Household Level ◽

Targeted Interventions ◽

Spatial Risk

AbstractMalaria risk is highly heterogeneous. Understanding village and household-level spatial heterogeneity of malaria risk can support a transition to spatially targeted interventions for malaria elimination. This analysis uses data from cross-sectional prevalence surveys conducted in 2014 and 2016 in two villages (Megiar and Mirap) in Papua New Guinea. Generalised additive modelling was used to characterise spatial heterogeneity of malaria risk and investigate the contribution of individual, household and environmental-level risk factors. Following a period of declining malaria prevalence, the prevalence of P. falciparum increased from 11.4 to 19.1% in Megiar and 12.3 to 28.3% in Mirap between 2014 and 2016, with focal hotspots observed in these villages in 2014 and expanding in 2016. Prevalence of P. vivax was similar in both years (20.6% and 18.3% in Megiar, 22.1% and 23.4% in Mirap) and spatial risk heterogeneity was less apparent compared to P. falciparum. Within-village hotspots varied by Plasmodium species across time and between villages. In Megiar, the adjusted odds ratio (AOR) of infection could be partially explained by household factors that increase risk of vector exposure, such as collecting outdoor surface water as a main source of water. In Mirap, increased AOR overlapped with proximity to densely vegetated areas of the village. The identification of household and environmental factors associated with increased spatial risk may serve as useful indicators of transmission hotspots and inform the development of tailored approaches for malaria control.

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Spatial prediction of malaria prevalence in Papua New Guinea: a comparison of Bayesian decision network and multivariate regression modelling approaches for improved accuracy in prevalence prediction

Malaria Journal ◽

10.1186/s12936-021-03804-0 ◽

2021 ◽

Vol 20 (1) ◽

Author(s):

Eimear Cleary ◽

Manuel W. Hetzel ◽

Paul Siba ◽

Colleen L. Lau ◽

Archie C. A. Clements

Keyword(s):

Logistic Regression ◽

Papua New Guinea ◽

Predictive Performance ◽

New Guinea ◽

Malaria Prevalence ◽

Multilevel Logistic Regression ◽

Bayesian Decision ◽

Logistic Regression Models ◽

Bayesian Decision Network ◽

Improved Accuracy

Abstract Background Considerable progress towards controlling malaria has been made in Papua New Guinea through the national malaria control programme’s free distribution of long-lasting insecticidal nets, improved diagnosis with rapid diagnostic tests and improved access to artemisinin combination therapy. Predictive prevalence maps can help to inform targeted interventions and monitor changes in malaria epidemiology over time as control efforts continue. This study aims to compare the predictive performance of prevalence maps generated using Bayesian decision network (BDN) models and multilevel logistic regression models (a type of generalized linear model, GLM) in terms of malaria spatial risk prediction accuracy. Methods Multilevel logistic regression models and BDN models were developed using 2010/2011 malaria prevalence survey data collected from 77 randomly selected villages to determine associations of Plasmodium falciparum and Plasmodium vivax prevalence with precipitation, temperature, elevation, slope (terrain aspect), enhanced vegetation index and distance to the coast. Predictive performance of multilevel logistic regression and BDN models were compared by cross-validation methods. Results Prevalence of P. falciparum, based on results obtained from GLMs was significantly associated with precipitation during the 3 driest months of the year, June to August (β = 0.015; 95% CI = 0.01–0.03), whereas P. vivax infection was associated with elevation (β = − 0.26; 95% CI = − 0.38 to − 3.04), precipitation during the 3 driest months of the year (β = 0.01; 95% CI = − 0.01–0.02) and slope (β = 0.12; 95% CI = 0.05–0.19). Compared with GLM model performance, BDNs showed improved accuracy in prediction of the prevalence of P. falciparum (AUC = 0.49 versus 0.75, respectively) and P. vivax (AUC = 0.56 versus 0.74, respectively) on cross-validation. Conclusions BDNs provide a more flexible modelling framework than GLMs and may have a better predictive performance when developing malaria prevalence maps due to the multiple interacting factors that drive malaria prevalence in different geographical areas. When developing malaria prevalence maps, BDNs may be particularly useful in predicting prevalence where spatial variation in climate and environmental drivers of malaria transmission exists, as is the case in Papua New Guinea.

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Iron nutrition and anaemia in a malaria-endemic environment: haematological investigation of the Gidra-speaking population in lowland Papua New Guinea

British Journal Of Nutrition ◽

10.1079/bjn19960040 ◽

1996 ◽

Vol 76 (3) ◽

pp. 333-346 ◽

Cited By ~ 2

Author(s):

Minato Nakazawa ◽

Ryutaro Ohtsuka ◽

Toshio Kawabe ◽

Tetsuro Hongo ◽

Tsukasa Inaoka ◽

...

Keyword(s):

Papua New Guinea ◽

Dietary Habits ◽

Transferrin Saturation ◽

New Guinea ◽

Malaria Prevalence ◽

Iron Nutrition ◽

Fe Deficiency ◽

Malaria Vectors ◽

Considerable Proportion ◽

Deficiency Anaemia

Blood examination was conducted for the four Gidra-speaking village groups in Papua New Guinea, who were characterized by high Fe intake and high malaria prevalence with marked inter-village differences. The northern riverine villagers, whose Fe intake was higher than the other three village groups, did not suffer from Fe-deficiency anaemia in their malaria-endemic environment; nor did the inland villagers, with their second highest Fe intake and their malaria-free environment, suffer from Fe-deficiency anaemia. However, several individuals of the southern riverine village suffered from anaemia in a malaria-endemic environment, although their Fe intake was almost the same as the inland villagers’. A considerable proportion of the coastal villagers were anaemic, reflecting the lowest Fe intake and the highest malaria prevalence. An inter-village comparison of the relationships between haemoglobiin levels and transferrin saturation revealed that the southern riverine villagers needed smaller amounts of circulating Fe for erythropoiesis than the northern riverine and inland villagers, reflecting the long-term human-environment conditions such as the density of malaria vectors and the people’s dietary habits. Fe supplementation was not judged effective against hypoferraemia and/or anaemia in such a population. As the incidence of malaria had no significant long-lasting effect on Fe stores or circulating Fe concentration, but did have an effect on anaemia, the hypothesis that malaria causes a transfer of Fe from the blood to parenchymal tissues as a defence against infectious diseases was not supported.

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Decreased bioefficacy of long-lasting insecticidal nets and the resurgence of malaria in Papua New Guinea

10.1101/2020.03.02.20030304 ◽

2020 ◽

Author(s):

Rebecca Vinit ◽

Lincoln Timinao ◽

Nakei Bubun ◽

Michelle Katusele ◽

Leanne Robinson ◽

...

Keyword(s):

Malaria Transmission ◽

Papua New Guinea ◽

New Guinea ◽

Time Frame ◽

Malaria Prevalence ◽

Drastic Reduction ◽

The World ◽

Confirmatory Tests ◽

Huge Impact ◽

Long Lasting Insecticidal Nets

AbstractBackgroundPapua New Guinea (PNG) has the highest malaria transmission outside of Africa and long-lasting insecticidal nets (LLINs) are the only vector-control tool distributed country-wide. LLINs were introduced into PNG in about 2006 and have been attributed to have had a huge impact on malaria transmission, with reductions in observed average malaria prevalence from 15.7% (2008) to 1% (2014). However, since 2015 malaria indicators in PNG have risen significantly. Similar trends have been observed in several African nations. In the present study, we observed a drastic reduction in bioefficacy of LLINs collected both from households as used nets and prior to use in original, unopened packaging. We hypothesise that decreased bioefficacy of LLIN is a major contributor to the observed malaria resurgence in PNG and possibly in other parts of the world.MethodsNew LLINs in original and unopened packaging (n=192) manufactured between 2007-2019 were collected in 15 PNG provinces. Used LLIN (n=40) manufactured between 2008 and 2017 were collected in 2 provinces. LLIN were subjected to standard WHO cone bioassays using fully susceptible An. farauti mosquitoes. A subset of LLIN was re-tested using fully susceptible An. gambiae G3 mosquitoes in order to ensure reproducibility of results.ResultsOnly 7% (95% CI 4-12%) of new LLINs manufactured between 2013-2019 exhibited 100% mortality. However, 84% (95%CI: 65-84%) new nets manufactured in 2012 or before exhibited 100% mortality. Only 29 % of used LLIN less than 3 years old exhibited > 80% 24h-mortality. Results obtained in tests using An. farauti corresponded well with confirmatory tests conducted using An. gambiae.DiscussionBioefficacy of LLIN in PNG appears to have been highly variable since 2013, with few nets manufactured since 2013 meeting WHO standards. This time-frame coincides with malaria resurgence in the country. These results may have ramifications for LLIN-based malaria control that go beyond the local PNG scenario.

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