Multilocus microsatellite genotyping of Plasmodium knowlesi isolates previously indicated 2 divergent parasite subpopulations in humans on the island of Borneo, each associated with a different macaque reservoir host species. Geographic divergence was also apparent, and independent sequence data have indicated particularly deep divergence between parasites from mainland Southeast Asia and Borneo. To resolve the overall population structure, multilocus microsatellite genotyping was conducted on a new sample of 182 P. knowlesi infections (obtained from 134 humans and 48 wild macaques) from diverse areas of Malaysia, first analyzed separately and then in combination with previous data. All analyses confirmed 2 divergent clusters of human cases in Malaysian Borneo, associated with long-tailed macaques and pig-tailed macaques, and a third cluster in humans and most macaques in peninsular Malaysia. High levels of pairwise divergence between each of these sympatric and allopatric subpopulations have implications for the epidemiology and control of this zoonotic species.

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Land conversion is understood to increase the risk of emergent zoonotic diseases. In simians and humans, infection risk has been linked to fragmented habitats. However, the role of fragmentation on disease dynamics in wildlife hosts is rarely quantified at macroecological scales due to the lack of systematic surveys. In Southeast Asia, non-human primates (NHPs) host Plasmodium knowlesi, a prominent zoonotic malaria. We examine reported primate P. knowlesi to investigate how landscape impacts parasite prevalence. Firstly, we conducted a meta-analysis of NHP P. knowlesi prevalence. Overall prevalence was 9.6% (CI95% 6.3-13.4), with considerable regional heterogeneity (I2=96.6%; CI95% 95.7-97.3) and high estimates in Borneo (52.4%, CI95% 22.8-81.3). Higher prevalence in NHPs shows clear spatial overlap with human infection foci. Secondly, environmental covariates were assembled from remote sensing data and statistical models were fitted to prevalence at multiple spatial scales. We demonstrate a strong relationship between forest fragmentation (20km, p<0.0001) and P. knowlesi in NHPs, suggesting that zoonotic malaria prevalence is maximised at intermediate levels of habitat complexity. Findings indicate a previously hypothesised trade-off between epidemiological and ecological mechanisms determining P. knowlesi infection in wildlife reservoirs, and that parasite prevalence in NHPs may be a key driver of human spillover risk.

In wildlife and humans, parasite infection has been linked to land conversion and fragmented habitat. However, zoonotic disease dynamics in wildlife hosts are rarely quantified at macroecological scales due to the lack of systematic surveys. Non-human primates (NHPs) host Plasmodium knowlesi, a zoonotic malaria with increasing public health impact and the main barrier to malaria elimination in Southeast Asia. Understanding of regional P. knowlesi infection dynamics in wildlife is limited. Here, we systematically assemble reports of NHP P. knowlesi and investigate how landscape impacts prevalence. Meta-analysis of 6322 NHPs from 148 sites highlights that prevalence is heterogeneous across Southeast Asia, with low overall prevalence and high estimates for Malaysian Borneo. Broadly, we find that regions exhibiting higher prevalence in NHPs overlap with human infection hotspots. By assembling remote sensing data and fitting generalised linear mixed models to prevalence at multiple spatial scales, we identify novel relationships between P. knowlesi in NHPs and forested landscapes. Preliminary evidence suggests that higher prevalence may be contingent on habitat complexity, which might explain geographic variation in parasite burden. Findings address critical gaps in understanding P. knowlesi epidemiology and indicate that prevalence in simian reservoirs may be a key spatial driver of human spillover risk.

In wildlife and humans, parasite infection has been linked to land conversion and fragmented habitat. However, zoonotic disease dynamics in wildlife hosts are rarely quantified at macroecological scales due to the lack of systematic surveys. Non-human primates (NHPs) host Plasmodium knowlesi, a zoonotic malaria with increasing public health impact and the main barrier to malaria elimination in Southeast Asia. Understanding of regional P. knowlesi infection dynamics in wildlife is limited. Here, we systematically assemble reports of NHP P. knowlesi and investigate how landscape impacts prevalence. Meta-analysis of 6322 NHPs from 148 sites highlights that prevalence is heterogeneous across Southeast Asia, with low overall prevalence and high estimates for Malaysian Borneo. Broadly, we find that regions exhibiting higher prevalence in NHPs overlap with human infection hotspots. By assembling remote sensing data and fitting generalised linear mixed models to prevalence at multiple spatial scales, we identify novel relationships between P. knowlesi in NHPs and forested landscapes. Preliminary evidence suggests that higher prevalence may be contingent on habitat complexity, which might explain geographic variation in parasite burden. Findings address critical gaps in understanding P. knowlesi epidemiology and indicate that prevalence in simian reservoirs may be a key spatial driver of human spillover risk.