Medical Biology - Research Publications

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Author: Koepfli, Cristian × Author: Mueller, Ivo × Author: Robinson, Leanne × End date: 2021 × Start date: 2020 × Type: Journal Article ×

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    Investigating differences in village-level heterogeneity of malaria infection and household risk factors in Papua New Guinea
    Gul, D ; Rodriguez-Rodriguez, D ; Nate, E ; Auwan, A ; Salib, M ; Lorry, L ; Keven, JB ; Katusele, M ; Rosado, J ; Hofmann, N ; Ome-Kaius, M ; Koepfli, C ; Felger, I ; Kazura, JW ; Hetzel, MW ; Mueller, I ; Karl, S ; Clements, ACA ; Fowkes, FJ ; Laman, M ; Robinson, LJ (NATURE PORTFOLIO, 2021-08-16)
    Malaria 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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    MonitoringPlasmodium falciparumandPlasmodium vivaxusing microsatellite markers indicates limited changes in population structure after substantial transmission decline in Papua New Guinea
    Kattenberg, JH ; Razook, Z ; Keo, R ; Koepfli, C ; Jennison, C ; Lautu-Gumal, D ; Fola, AA ; Ome-Kaius, M ; Barnadas, C ; Siba, P ; Felger, I ; Kazura, J ; Mueller, I ; Robinson, LJ ; Barry, AE (WILEY, 2020-12)
    Monitoring the genetic structure of pathogen populations may be an economical and sensitive approach to quantify the impact of control on transmission dynamics, highlighting the need for a better understanding of changes in population genetic parameters as transmission declines. Here we describe the first population genetic analysis of two major human malaria parasites, Plasmodium falciparum (Pf) and Plasmodium vivax (Pv), following nationwide distribution of long-lasting insecticide-treated nets (LLINs) in Papua New Guinea (PNG). Parasite isolates from pre- (2005-2006) and post-LLIN (2010-2014) were genotyped using microsatellite markers. Despite parasite prevalence declining substantially (East Sepik Province: Pf = 54.9%-8.5%, Pv = 35.7%-5.6%, Madang Province: Pf = 38.0%-9.0%, Pv: 31.8%-19.7%), genetically diverse and intermixing parasite populations remained. Pf diversity declined modestly post-LLIN relative to pre-LLIN (East Sepik: Rs  = 7.1-6.4, HE  = 0.77-0.71; Madang: Rs  = 8.2-6.1, HE  = 0.79-0.71). Unexpectedly, population structure present in pre-LLIN populations was lost post-LLIN, suggesting that more frequent human movement between provinces may have contributed to higher gene flow. Pv prevalence initially declined but increased again in one province, yet diversity remained high throughout the study period (East Sepik: Rs  = 11.4-9.3, HE  = 0.83-0.80; Madang: Rs  = 12.2-14.5, HE  = 0.85-0.88). Although genetic differentiation values increased between provinces over time, no significant population structure was observed at any time point. For both species, a decline in multiple infections and increasing clonal transmission and significant multilocus linkage disequilibrium post-LLIN were positive indicators of impact on the parasite population using microsatellite markers. These parameters may be useful adjuncts to traditional epidemiological tools in the early stages of transmission reduction.