Malaria parasites in macaques in Thailand: stump-tailed macaques (Macaca arctoides) are new natural hosts for Plasmodium knowlesi, Plasmodium inui, Plasmodium coatneyi and Plasmodium fieldi

Abstract

Background Certain species of macaques are natural hosts of Plasmodium knowlesi and Plasmodium cynomolgi, which can both cause malaria in humans, and Plasmodium inui, which can be experimentally transmitted to humans. A significant number of zoonotic malaria cases have been reported in humans throughout Southeast Asia, including Thailand. There have been only two studies undertaken in Thailand to identify malaria parasites in non-human primates in 6 provinces. The objective of this study was to determine the prevalence of P. knowlesi, P. cynomolgi, P. inui, Plasmodium coatneyi and Plasmodium fieldi in non-human primates from 4 new locations in Thailand. Methods A total of 93 blood samples from Macaca fascicularis, Macaca leonina and Macaca arctoides were collected from four locations in Thailand: 32 were captive M. fascicularis from Chachoengsao Province (CHA), 4 were wild M. fascicularis from Ranong Province (RAN), 32 were wild M. arctoides from Prachuap Kiri Khan Province (PRA), and 25 were wild M. leonina from Nakornratchasima Province (NAK). DNA was extracted from these samples and analysed by nested PCR assays to detect Plasmodium, and subsequently to detect P. knowlesi, P. coatneyi, P. cynomolgi, P. inui and P. fieldi. Results Twenty-seven of the 93 (29%) samples were Plasmodium-positive by nested PCR assays. Among wild macaques, all 4 M. fascicularis at RAN were infected with malaria parasites followed by 50% of 32 M. arctoides at PRA and 20% of 25 M. leonina at NAK. Only 2 (6.3%) of the 32 captive M. fascicularis at CHA were malaria-positive. All 5 species of Plasmodium were detected and 16 (59.3%) of the 27 macaques had single infections, 9 had double and 2 had triple infections. The composition of Plasmodium species in macaques at each sampling site was different. Macaca arctoides from PRA were infected with P. knowlesi, P. coatneyi, P. cynomolgi, P. inui and P. fieldi. Conclusions The prevalence and species of Plasmodium varied among the wild and captive macaques, and between macaques at 4 sampling sites in Thailand. Macaca arctoides is a new natural host for P. knowlesi, P. inui, P. coatneyi and P. fieldi.

Zoonotic pathogens survey in free-living long-tailed macaques in Thailand

“…The limitations of this study are that nucleotide sequencing and phylogenetic tree construction of SFV and P. inui were not performed because SFV and P. inui are generally found in Thai macaques [ 9 , 42 , 43 , 45 ] as well as natural infection with SFV and P. inui in humans is still very rare (1–5% for SFV and 2.82% for P. inui ) and asymptomatic [ 10 , 15 ]. The public health burden of such pathogens needs to be further investigated in the future…”

Plasmodium knowlesi: the game changer for malaria eradication

“…However, it should be noted that P. knowlesi has yet to be found in M. leonina (Table 2 ). Meanwhile, P. knowlesi was found in a stump-tailed macaque ( M. arctoides ) in Prachuap Kiri Khan province, Thailand, based on nested PCR method without further backing of evidence by the gold standard microscopy or other molecular tools like sequencing [ 61 ]. In another study, P. knowlesi was detected in a dusky leaf monkey ( Semnopithecus obscurus ), as confirmed by sequencing and phylogenetic analysis [ 60 ].…”

Case Series of Three Malaria Patients From Thailand Infected With the Simian Parasite, Plasmodium Cynomolgi

“…At the follow-up visits by the Yala study team, Case A and B did report the presence of macaques near their homes. In Thailand, the main hosts of P. cynomolgi, P. knowlesi, P. inui, and P. coatneyi are Macaca fasicularis and M. nemestrina, with recent reports in stump-tailed macaques, M. arctoides [12]. Co-infections of simian malaria are not uncommon in macaques, with the presence of two or three species simultaneously detected in 18-40% of monkeys [12,13], which may explain why some human studies report co-infections more than mono-infections [2,5].…”

“…In Thailand, the main hosts of P. cynomolgi, P. knowlesi, P. inui, and P. coatneyi are Macaca fasicularis and M. nemestrina, with recent reports in stump-tailed macaques, M. arctoides [12]. Co-infections of simian malaria are not uncommon in macaques, with the presence of two or three species simultaneously detected in 18-40% of monkeys [12,13], which may explain why some human studies report co-infections more than mono-infections [2,5]. P. cynomolgi was rst reported as a mono-infection in a Malaysian woman in 2014 [1], and up to now, cases have been shown to exist in both peninsular Malaysia and Borneo Malaysia, the latter where P. knowlesi, another simian malaria is endemic [5,7].…”