BACKGROUND: A case of human infection with Plasmodium knowlesi has been recently discovered in Thailand. To investigate the prevalence of this malaria species, a molecular-based survey was performed. METHODS: Blood samples from 1874 patients were tested for Plasmodium species by microscopy and nested polymerase chain reaction. P. knowlesi was characterized by sequencing the merozoite surface protein 1 gene (msp-1). RESULTS: Of all Plasmodium species identified, P. falciparum, P. vivax, P. malariae, P. ovale, and P. knowlesi contributed 43.52%, 68.08%, 1.37%, 1.03%, and 0.57%, respectively. Mixed-species infections were more common in northwestern and southwestern regions bordering Myanmar (23%-24%) than in eastern and southern areas (3%-5%). In northwestern and southwestern regions, mixed-species infections had a significantly higher prevalence in dry than in rainy seasons (P < .001). P. knowlesi was found in 10 patients, mostly from southern and southwestern areas-9 were coinfected with either P. falciparum or P. vivax. Most of the P. knowlesi Thai isolates were more closely related to isolates from macaques than to isolates from Sarawak patients. The msp-1 sequences of isolates from the same area of endemicity differed and possessed novel sequences, indicating genetic polymorphism in P. knowlesi infecting humans. CONCLUSIONS: This survey highlights the widespread distribution of P. knowlesi in Thailand, albeit at low prevalence and mostly occurring as cryptic infections.
BACKGROUND: A case of human infection with Plasmodium knowlesi has been recently discovered in Thailand. To investigate the prevalence of this malaria species, a molecular-based survey was performed. METHODS: Blood samples from 1874 patients were tested for Plasmodium species by microscopy and nested polymerase chain reaction. P. knowlesi was characterized by sequencing the merozoite surface protein 1 gene (msp-1). RESULTS: Of all Plasmodium species identified, P. falciparum, P. vivax, P. malariae, P. ovale, and P. knowlesi contributed 43.52%, 68.08%, 1.37%, 1.03%, and 0.57%, respectively. Mixed-species infections were more common in northwestern and southwestern regions bordering Myanmar (23%-24%) than in eastern and southern areas (3%-5%). In northwestern and southwestern regions, mixed-species infections had a significantly higher prevalence in dry than in rainy seasons (P < .001). P. knowlesi was found in 10 patients, mostly from southern and southwestern areas-9 were coinfected with either P. falciparum or P. vivax. Most of the P. knowlesi Thai isolates were more closely related to isolates from macaques than to isolates from Sarawak patients. The msp-1 sequences of isolates from the same area of endemicity differed and possessed novel sequences, indicating genetic polymorphism in P. knowlesi infecting humans. CONCLUSIONS: This survey highlights the widespread distribution of P. knowlesi in Thailand, albeit at low prevalence and mostly occurring as cryptic infections.
Authors: Balbir Singh; Lee Kim Sung; Asmad Matusop; Anand Radhakrishnan; Sunita S G Shamsul; Janet Cox-Singh; Alan Thomas; David J Conway Journal: Lancet Date: 2004-03-27 Impact factor: 79.321
Authors: Hans-Peter Fuehrer; Peter Starzengruber; Paul Swoboda; Wasif Ali Khan; Julia Matt; Benedikt Ley; Kamala Thriemer; Rashidul Haque; Emran Bin Yunus; Shah Monir Hossain; Julia Walochnik; Harald Noedl Journal: Am J Trop Med Hyg Date: 2010-07 Impact factor: 2.345
Authors: O Oddoux; A Debourgogne; A Kantele; C H Kocken; T S Jokiranta; S Vedy; J M Puyhardy; M Machouart Journal: Eur J Clin Microbiol Infect Dis Date: 2010-12-15 Impact factor: 3.267
Authors: Peter Van den Eede; Hong Nguyen Van; Chantal Van Overmeir; Indra Vythilingam; Thang Ngo Duc; Le Xuan Hung; Hung Nguyen Manh; Jozef Anné; Umberto D'Alessandro; Annette Erhart Journal: Malar J Date: 2009-10-30 Impact factor: 2.979