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.
Highlights
Plasmodium knowlesi is a species of malaria parasite found in wild macaque populations which is the main cause of human malaria in Malaysian Borneo
Spatial patterns and risk factors for P. knowlesi differed from other malaria species, highlighting the need for knowlesi specific disease control measures
After the initial recognition of a large number of human cases of the zoonotic malaria Plasmodium knowlesi in 2004 and advent of routine diagnosis of malaria cases by molecular methods, increasing numbers of human P. knowlesi cases have been reported in Southeast Asia and P. knowlesi is the most common cause of human malaria in Malaysian Borneo [1,2,3]
Summary
After the initial recognition of a large number of human cases of the zoonotic malaria Plasmodium knowlesi in 2004 and advent of routine diagnosis of malaria cases by molecular methods, increasing numbers of human P. knowlesi cases have been reported in Southeast Asia and P. knowlesi is the most common cause of human malaria in Malaysian Borneo [1,2,3]. Despite increasing amounts of data available for symptomatic malaria cases presenting at hospital facilities, little is known about patterns of P. knowlesi exposure and infection at a community level [4]. Targeting resources to identify and control P. knowlesi requires a detailed understanding of environmental and social risk factors. Associations between deforestation and increases in village-level incidence have been shown for clinical cases but this may not fully reflect exposure in the wider community [9]. Rural populations, the zoonotic malaria Plasmodium knowlesi is 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
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