Gul, D., Rodriguez Rodriguez, D., Nate, E., Hoffman, N., Koepfli, C., Salib, M., Karl, S., Hetzel, M., Mueller, I., Clements, A., Fowkes, F., Laman, M., and Robinson, L. (2021) Investigating within-village spatial heterogeneity of malaria infection over time on the north-coast of Papua New Guinea. International Journal of Infectious Diseases, 101 (S1). p. 434.

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Abstract

Background: As transmission declines, the distribution of malaria burden and ongoing transmission have been observed to become spatially clustered such that targeted interventions have been proposed to accelerate malaria control and elimination. Reductions in the nationwide prevalence of malaria in Papua New Guinea (PNG) observed after the scale-up of control interventions were not uniform across the country with substantial heterogeneity observed in many areas. To achieve further reductions, understanding the spatial and temporal heterogeneity and its drivers of transmission at village level will be important.

Methods & Materials: Two community cross-sectional malaria prevalence surveys were conducted in 2014 and 2016 in two villages – Megiar and Mirap on the north coast of Madang province. These surveys collected data onPlasmodium spp. infection prevalence (as detected by qPCR and light microscopy), GPS location, household and behavioural characteristics. Spatial analysis (SaTScan) was conducted to determine if areas of high malaria burden (AHMBs) for Plasmodium spp. infections existed at the village level and changes between timepoints were compared. Regression models were used to investigate associations between specific risk factors and infection in these AHMBs.

Results: Malaria prevalence by qPCR increased from 30.7% to 34.8% and from 32.1% to 46.4% in Megiar and Mirap respectively. Distinct AHMBs were detected at both timepoints. In Megiar, AHMBs accounted for more than 50% of the malaria burden and their locations were stable across timepoints but increased in size in 2016. AHMBs in 2016 were associated with households of lower socio-economic status (SES) and those that used surface water as their primary drinking water source. In Mirap, AHMBs were small, accounting for less than 20% of total malaria burden in the village.

Conclusion: Spatially-defined AHMBs exist within villages and may be spatially stable across time but expand or contract as prevalence and transmission changes. These AHMBs may account for more than 50% of all malaria burden in the village. Low SES and time spent outdoors may be risk factors for exposure in these AHMBs. This study provides rationale for further investigation to develop tailored spatially-targeted interventions that could be a cost-effectivemethod to further reduce transmission in these areas.

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