Natural Plasmodium infection in wild macaques of three states in peninsular Malaysia

Abstract

Zoonotic cases of Plasmodium knowlesi account for most malaria cases in Malaysia, and humans infected with P. cynomolgi, another parasite of macaques have recently been reported in Sarawak. To date the epidemiology of malaria in its natural Macaca reservoir hosts remains little investigated. In this study we surveyed the prevalence of simian malaria in wild macaques of three states in Peninsular Malaysia, namely Pahang, Perak and Johor using blood samples from 103 wild macaques (collected by the Department of Wildlife and National Parks Peninsular Malaysia) subjected to microscopic examination and nested PCR targeting the Plasmodium small subunit ribosomal RNA gene. As expected, PCR analysis yielded significantly higher prevalence (64/103) as compared to microscopic examination (27/103). No relationship between the age and/or sex of the macaques with the parasitaemia and the Plasmodium species infecting the macaques could be identified. Wild macaques in Pahang had the highest prevalence of Plasmodium parasites (89.7%), followed by those of Perak (69.2%) and Johor (28.9%). Plasmodium inui and P. cynomolgi were the two most prevalent species infecting the macaques from all three states. Half of the macaques (33/64) harboured two or more Plasmodium species. These data provide a baseline survey, which should be extended by further longitudinal investigations that should be associated with studies on the bionomics of the anopheline vectors. This information will allow an accurate evaluation of the risk of zoonotic transmission to humans, and to elaborate effective strategies to control simian malaria.

Preliminary review on the prevalence, proportion, geographical distribution, and characteristics of naturally acquired Plasmodium cynomolgi infection in mosquitoes, macaques, and humans: a systematic review and meta-analysis

“…Finally, 13 studies were included in the present study. Out of the 13 studies selected, 7 studies [11][12][13][14][15][16][17] reporting on P. cynomolgi infection in macaques, 3 studies [18][19][20] reporting on P. cynomolgi infection in humans, and 3 studies [21][22][23] reporting on P. cynomolgi infection in mosquitoes were included in the final analysis.…”

“…The characteristics of the included studies are shown in Table 1. Thirteen studies [11][12][13][14][15][16][17][18][19][20][21][22][23] reporting the prevalence or incidence of naturally acquired P. cynomolgi in humans (3 studies, 21 cases), mosquitoes (3 studies, 26 cases), and macaques (7 studies, 334 cases) were included for qualitative and quantitative syntheses. Details of P. cynomolgi mono and mixed infections in humans, Anopheles, and macaques are shown in Table 2.…”

“…Among the 7 studies reporting on 334 macaques infected with P. cynomolgi between 2004 and 2019, 4 studies (57.1%) [11,12,15,16] were conducted in Malaysia, 1 in the Philippines [13], and 1 in Singapore [14]. Fig.…”

“…Twelve studies were from the database searches, and one study was from the searches of review articles Another study [17] was conducted in five countries, including the Philippines, Indonesia, Singapore, Cambodia, and Laos. Four studies [11,13,14,17] identified Plasmodium species in long-tailed macaques, while 3 studies [12,14,16] identified Plasmodium species in both longtailed and pig-tailed macaques. All studies used nested PCR for amplification of the 18S rRNA gene except a study by Muehlenbein et al [16], which used nested PCR for amplification of the cytochrome b (cytb) gene.…”

Natural Plasmodium inui Infections in Humans and Anopheles cracens Mosquito, Malaysia

“…P. inui has a wide geographic range in Asia, including southern India, Southeast Asia, and Taiwan ( 13 ). A surveillance study reported that the prevalence of P. inui among wild macaques in Pahang was 66.7% (26/39 macaques sampled); 76.9% of these infections were co-infections with other Plasmodium species ( 14 ). Given the high prevalence of P. inui among macaques and natural Anopheles mosquito vectors ( 2 ), humans could be exposed to P. inui via vectorborne transmission from infected macaques, particularly at a location where humans, macaque hosts, and mosquito vectors co-exist.…”