Plasmodium knowlesi: Emergent Human Malaria in Southeast Asia
Plasmodium knowlesi is an emerging malaria parasite in humans and is unique to Southeast Asia. Since most countries in Southeast Asia are working towards elimination of malaria, it is important to have knowledge on this emerging simian malaria parasite af
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Plasmodium knowlesi: Emergent Human Malaria in Southeast Asia Kim-Sung Lee and Indra Vythilingam
Abstract Plasmodium knowlesi is an emerging malaria parasite in humans and is unique to Southeast Asia. Since most countries in Southeast Asia are working towards elimination of malaria, it is important to have knowledge on this emerging simian malaria parasite affecting humans. The first case of simian malaria was reported in Malaysia in 1965. At that time extensive work conducted did not reveal other simian malaria cases in humans. However, in 2004, a large focus of P. knowlesi was reported from Sarawak, Malaysian Borneo and that led to many studies and cases being reported from most countries in Southeast Asia. In this chapter, the history, epidemiology, diagnosis, vectors and role of simian host are discussed. Malaria is now a zoonosis and the challenges facing the countries of Southeast in tackling the knowlesi malaria situation and the way forward have been documented.
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Introduction
Malaria is a mosquito-borne disease caused by the protozoan parasite of the genus Plasmodium. To date, there are nearly 200 species of Plasmodium known to infect a wide range of hosts [1]. These include malaria parasite species that infect mammals, rodents, birds and reptiles. There are five species of Plasmodium known to infect and cause malaria in humans, namely Plasmodium falciparum, P. vivax, P. malariae, P. ovale and P. knowlesi [2, 3]. Of these, P. falciparum is well known to be the deadliest form of human malaria, whereas P. vivax is the most prevalent
K.-S. Lee Environmental Health Institute, National Environment Agency, Singapore I. Vythilingam (*) University of Malaya, Kuala Lumpur, Malaysia e-mail: [email protected] Y.A.L. Lim and I. Vythilingam (eds.), Parasites and their vectors, DOI 10.1007/978-3-7091-1553-4_2, © Springer-Verlag Wien 2013
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and widely distributed species of human malaria [4, 5]. In general, malaria caused by P. vivax, P. malariae and P. ovale is milder and rarely fatal. The fifth species of human malaria, P. knowlesi, which received much attention only in the last decade, is a malaria species of non-human primate origin [3, 6, 7]. Plasmodium knowlesi is prevalent in Southeast Asia and is the cause of human malaria with symptoms ranging from mild to severe disease [8]. Previously, naturally acquired human infections with malaria species of zoonotic origin were considered rare, and it was believed that humans are likely the accidental hosts. This perception changed after it was discovered that a large number of human cases of P. knowlesi malaria were routinely misdiagnosed as P. malariae in the Kapit division of Sarawak, Malaysian Borneo [2, 9]. Following this first report, it was later discovered that human knowlesi malaria is widespread as human cases were identified throughout Southeast Asia with the exception of Lao PDR. In this chapter, a special focus is given to the epidemiology and emergence of P. knowlesi in Southeast Asia. Several aspects of this simian p
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