Exposure and infection to Plasmodium knowlesi in case study communities in Northern Sabah, Malaysia and Palawan, The Philippines

Abstract

BackgroundPrimarily impacting poor, rural populations, the zoonotic malaria Plasmodium knowlesi is now the main cause of human malaria within Malaysian Borneo. While data is increasingly available on symptomatic cases, little is known about community-level patterns of exposure and infection. Understanding the true burden of disease and associated risk factors within endemic communities is critical for informing evidence-based control measures.Methodology/Principal findingsWe conducted comprehensive surveys in three areas where P. knowlesi transmission is reported: Limbuak, Pulau Banggi and Matunggung, Kudat, Sabah, Malaysia and Bacungan, Palawan, the Philippines. Infection prevalence was low with parasites detected by PCR in only 0.2% (4/2503) of the population. P. knowlesi PkSERA3 ag1 antibody responses were detected in 7.1% (95% CI: 6.2–8.2%) of the population, compared with 16.1% (14.6–17.7%) and 12.6% (11.2–14.1%) for P. falciparum and P. vivax. Sero-prevalence was low in individuals <10 years old for P. falciparum and P. vivax consistent with decreased transmission of non-zoonotic malaria species. Results indicated marked heterogeneity in transmission intensity between sites and P. knowlesi exposure was associated with agricultural work (OR 1.63; 95% CI 1.07–2.48) and higher levels of forest cover (OR 2.40; 95% CI 1.29–4.46) and clearing (OR 2.14; 95% CI 1.35–3.40) around houses. Spatial patterns of P. knowlesi exposure differed from exposure to non-zoonotic malaria and P. knowlesi exposed individuals were younger on average than individuals exposed to non-zoonotic malaria.Conclusions/SignificanceThis is the first study to describe serological exposure to P. knowlesi and associated risk factors within endemic communities. Results indicate community–level patterns of infection and exposure differ markedly from demographics of reported cases, with higher levels of exposure among women and children. Further work is needed to understand these variations in risk across a wider population and spatial scale.

Development and validation of serological markers for detecting recent exposure toPlasmodium vivaxinfection

“…The same is likely to apply to P. malariae and P. ovale infections, which regularly occur in mixed species infections (49), and of which the latter also has dormant hypnozoites. Given the marked difference in patterns of exposure to the zoonotic P. knowlesi (50), cross-reactivity between P. vivax and P. knowlesi would be significantly more problematic (51).…”

Local human movement patterns and land use impact exposure to zoonotic malaria in Malaysian Borneo

“…This study was conducted in two rural communities in Northern Sabah, Malaysia: Matunggong, Kudat (6°47N, 116°48E, population: 1260) and Limbuak, Pulau Banggi (7°09N, 117°05E, population: 1009) (Figure 2). These areas were the focus for integrated entomology, primatology and social science studies for risk factors for P. knowlesi (https://www.lshtm.ac.uk/research/centres-projects-groups/monkeybar), with clinical cases and submicroscopic infections reported from both sites and P. knowlesi sero-prevalence estimated as 6.8% and 11.7% in Matunggong and Limbuak respectively (30).…”

“…A. Location of study sites and tracked houses (households with one or more individual GPS tracked) and survey houses (households with only questionnaire data collected and used for prediction) in B. Matunggong, Kudat and C. Limbuak, Banggi; description of land cover classification and survey methodology in (30)…”

“…Demographic data and GPS locations of primary residences were collected for all individuals residing in these areas (30). Potential spatial and environmental covariates for these sites were assembled from ground-based and remote-sensing data sources (Supplementary Table 1).…”

“…Focusing on one aspect of land use, human movement and time spent within different land cover types, we explored the role of heterogeneity in local space use on disease exposure. Rolling cross-sectional GPS tracking surveys were conducted in two study areas with on-going P. knowlesi transmission in Northern Sabah, Malaysia (Matunggong and Limbuak (30)). We aimed to characterise local movement patterns and identify individuals and locations associated with increased P. knowlesi exposure risks by: 1. analysing individual movement patterns and developing predictive maps of human space use relative to spatial and environmental factors, 2. modelling biting rates of the main vector An.…”