First case of detection of Plasmodium knowlesi in Spain by Real Time PCR in a traveller from Southeast Asia

Recent reports from Asia suggest the possibility that Plasmodium knowlesi, is emerging as an important zoonotic human pathogen [1]. The natural hosts of P. knowlesi are the long-tailed (Macaca fascicularis) and pig-tailed (Macaca nemestrina) macaques [2], commonly found in Southeast Asia. Plasmodium knowlesi has a quotidian (24 h) asexual blood cycle, the shortest among primate malarias and produces daily fever peaks in its hosts, causing severe malaria if not treated [3]. At present, P. knowlesi transmission is restricted to the Anopheles leucosphyrus group of mosquitoes, which currently comprises 20 species [4]. The range of the A. leucosphyrus group overlaps with the long-tailed and pig-tailed macaques, and naturally acquired within this range. Plasmodium knowlesi was first described in 1931; in 1932 was experimentally shown to be infectious to humans [3]. The first natural infection in humans was reported in 1965 [5] in a man from the United States after a visit to Peninsular Malaysia. In 1971, there was a presumptive case in a man of Malaysia [6]. No other reports were published on naturally acquired P. knowlesi infections in humans until 2004 [3]. Plasmodium knowlesi infections in human are not exclusive to Malaysia, but can also appear in China [7], in Thailand [8], Philippines [9], Singapore [10] and Indonesian Borneo [11]. Plasmodium knowlesi can be misidentified on a blood smear as the morphology of the blood-stage forms share similarities with Plasmodium malariae and Plasmodium falciparum, such as "bands forms" attributed to P. malariae, and delicate ring forms as seen with P. falciparum infections [2,12]. Currently, PCR assay and molecular characterization are the most reliable methods for detecting and diagnosing P. knowlesi infection [13-15]. Rapid diagnostic tests kits may or may not recognize P. knowlesi because of their specificity [16,17]. The disease can be treated using already existing anti-malarial therapy such as mefloquine and chloroquine. Th