Current status of Plasmodium knowlesi vectors: a public health concern? I. VYTHILINGAM* , M. L. WONG and W. S. WAN-YUSSOF Parasitology Department, Faculty of Medicine, University of Malaya, Lembah Pantai, 50603 Kuala Lumpur, Malaysia (Received 16 February 2016; revised 31 March 2016; accepted 21 April 2016; first published online 25 May 2016) SUMMARY Plasmodium knowlesi a simian malaria parasite is currently affecting humans in Southeast Asia. Malaysia has reported the most number of cases and P. knowlesi is the predominant species occurring in humans. The vectors of P. knowlesi belong to the Leucosphyrus group of Anopheles mosquitoes. These are generally described as forest-dwelling mosquitoes. With de- forestation and changes in land-use, some species have become predominant in farms and villages. However, knowledge on the distribution of these vectors in the country is sparse. From a public health point of view it is important to know the vectors, so that risk factors towards knowlesi malaria can be identified and control measures instituted where possible. Here, we review what is known about the knowlesi malaria vectors and ascertain the gaps in knowledge, so that future studies could concentrate on this paucity of data in-order to address this zoonotic problem. Key words: malaria, vectors, forest, zoonosis, Anopheles, Plasmodium knowlesi. INTRODUCTION On a global scale there has been substantial progress in reducing malaria morbidity and mortality with both decreasing by 37 and 48%, respectively in the past decade (WHO, 2015). Overall countries in the Asia-Pacific region have reduced their malaria cases by 76% (Cotter et al. 2013). Thus, most countries in the Asia-Pacific region are now working towards elimination of malaria (Cotter et al. 2013). However, Plasmodium knowlesi, a simian malaria parasite has been found infecting humans in all countries in Southeast Asia with the exception of Lao PDR and Timor Leste (Jongwutiwes et al. 2004; Singh et al. 2004; Cox Singh et al. 2008; Luchavez et al. 2008; Ng et al. 2008; Vythilingam et al. 2008; Eede et al. 2009; Figtree et al. 2010; Jiang et al. 2010; Khim et al. 2011; William et al. 2013; Yusof et al. 2014). In Malaysia, P. knowlesi forms 38% of the reported malaria cases (MOH, 2012). The success of the malaria control programme has been due to active case detection, better diagnosis and treatment coupled with vector control measures such as indoor residual spraying and insecticide- treated bed nets (Yukich et al. 2008). Anopheles mos- quitoes are responsible for the spread of malaria and the species responsible have been well documented (Sinka et al. 2011). Knowlesi malaria, which is a zoo- nosis, is currently reported from countries where Leucosphyrus group of Anopheles mosquitoes are present along with the simian hosts the long-tailed and the pig-tailed macaques (Moyes et al. 2014). Incrimination of the vectors of simian malaria is the first step in understanding their role and subse- quently choosing appropriate control measures required to target their specific behaviour. However, although cases of knowlesi malaria have been reported throughout Malaysia and Southeast Asia, studies on the vectors of P. knowlesi are limited (Vythilingam, 2012; Vythilingam and Hii, 2013). Due to this paucity of data risk factors asso- ciated with P. knowlesi remain unknown. VECTORIAL STATUS AND GEOGRAPHIC DISTRIBUTION OF LEUCOSPHYRUS GROUP OF ANOPHELES MOSQUITOES Only Anopheles mosquitoes belonging to the Leucosphyrus group have been reported as vectors of simian malaria (Vythilingam and Hii, 2013). The Leucosphyrus group consists of three sub- groups: Leucosphyrus, Hackeri and Riparis. According to (Sallum et al. 2005; Manguin et al. 2008), the Leucosphyrus subgroup consists of the Dirus and Leucosphyrus complexes, which includes eight and five sibling species, respectively. Species belonging to the Leucosphyrus complex are also im- portant vectors of human malaria and lymphatic filariasis (Manguin et al. 2010) and are distributed in the South and Southeast Asia regions. The current vectorial status and geographical distribu- tion of the Leucosphyrus group are listed in Table 1 which has been modified and updated from (Sallum et al. 2005; Vythilingam and Hii, 2013). * Corresponding author: Parasitology Department, Faculty of Medicine, University of Malaya, Lembah Pantai, 50603 Kuala Lumpur, Malaysia. E-mail: indra. vythilingam@gmail.com 32 SPECIAL ISSUE REVIEW Parasitology (2018), 145, 32–40. © Cambridge University Press 2016 doi:10.1017/S0031182016000901 https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0031182016000901 Downloaded from https://www.cambridge.org/core. National University of Singapore (NUS), on 05 Feb 2018 at 14:36:36, subject to the Cambridge Core terms of use, available at