Human Plasmodium knowlesi infection in Ranong province, southwestern border of Thailand

• Published in: Malaria Journal
• Main Authors: Sermwittayawong Natthawan, Singh Balbir, Nishibuchi Mitsuaki, Sawangjaroen Nongyao, Vuddhakul Varaporn
• Format: Article in Journal/Newspaper
• Language: English
• Published: BMC 2012
• Subjects: Plasmodium knowlesi; Thailand; Myanmar; Circumsporozoite protein; Arctic medicine. Tropical medicine; RC955-962; Infectious and parasitic diseases; RC109-216; Arctic
• Online Access: https://doi.org/10.1186/1475-2875-11-36; https://doaj.org/article/88a6c1830b914d9bbc8856d2ee060fc4

Abstract Background Plasmodium knowlesi , a simian malaria parasite, has been reported in humans in many Southeast Asian countries. In Thailand, most of the limited numbers of cases reported so far were from areas near neighbouring countries, including Myanmar. Methods Blood samples collected from 171 Thai and 248 Myanmese patients attending a malaria clinic in Ranong province, Thailand, located near the Myanmar border were investigated for P. knowlesi using nested PCR assays. Positive samples were also investigated by PCR for Plasmodium falciparum, Plasmodium vivax, Plasmodium malariae and Plasmodium ovale , and were confirmed by sequencing the gene encoding the circumsporozoite protein ( csp ). Results Two samples, one obtained from a Thai and the other a Myanmese, were positive for P. knowlesi only. Nucleotide sequences of the csp gene derived from these two patients were identical and phylogenetically indistinguishable from other P. knowlesi sequences derived from monkeys and humans. Both patients worked in Koh Song, located in the Kawthoung district of Myanmar, which borders Thailand. Conclusion This study indicates that transmission of P. knowlesi is occurring in the Ranong province of Thailand or the Kawthoung district of Myanmar. Further studies are required to assess the incidence of knowlesi malaria and whether macaques in these areas are the source of the infections.