Differential prevalence of Plasmodium infections and cryptic Plasmodium knowlesi malaria in humans in Thailand.

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.

[1]  A. Hughes,et al.  Differential selective pressures on the merozoite surface protein 2 locus of Plasmodium falciparum in a low endemic area. , 2008, Gene.

[2]  Y. Leo,et al.  Naturally Acquired Human Plasmodium knowlesi Infection, Singapore , 2008, Emerging infectious diseases.

[3]  P. Chiodini,et al.  Human Infections with Plasmodium knowlesi, the Philippines , 2008, Emerging Infectious Diseases.

[4]  L. Cui,et al.  Malaria and Hepatocystis species in wild macaques, southern Thailand. , 2008, The American journal of tropical medicine and hygiene.

[5]  C. Putaporntip,et al.  Positive selection on the Plasmodium falciparum sporozoite threonine-asparagine-rich protein: analysis of isolates mainly from low endemic areas. , 2008, Gene.

[6]  D. Conway,et al.  Plasmodium knowlesi malaria in humans is widely distributed and potentially life threatening. , 2008, Clinical infectious diseases : an official publication of the Infectious Diseases Society of America.

[7]  Y. Leo,et al.  Naturally Acquired Human Plasmodium knowlesi Infection , 2008 .

[8]  H. Kishino,et al.  Recent independent evolution of msp1 polymorphism in Plasmodium vivax and related simian malaria parasites. , 2007, Molecular and biochemical parasitology (Print).

[9]  M. Nei,et al.  MEGA4: Molecular Evolutionary Genetics Analysis (MEGA) software version 4.0. , 2007, Molecular biology and evolution.

[10]  H. D. del Portillo,et al.  Origins of sequence diversity in the malaria vaccine candidate merozoite surface protein-2 (MSP-2) in Amazonian isolates of Plasmodium falciparum. , 2006, Gene.

[11]  A. Hughes,et al.  Ancient common ancestry of the merozoite surface protein 1 of Plasmodium vivax as inferred from its homologue in Plasmodium knowlesi. , 2006, Molecular and biochemical parasitology.

[12]  Jetsumon Sattabongkot,et al.  Spatio-temporal distribution of Plasmodium falciparum and p. Vivax malaria in Thailand. , 2005, The American journal of tropical medicine and hygiene.

[13]  T. Sata,et al.  Naturally Acquired Plasmodium knowlesi Malaria in Human, Thailand , 2004, Emerging infectious diseases.

[14]  Imelda Bates,et al.  Malaria misdiagnosis: effects on the poor and vulnerable , 2004, The Lancet.

[15]  J. Hugot,et al.  Evolutionary relationships between 15 Plasmodium species from New and Old World primates (including humans): a 18S rDNA cladistic analysis , 2004, Parasitology.

[16]  G. Snounou,et al.  The co-existence of Plasmodium: sidelights from falciparum and vivax malaria in Thailand. , 2004, Trends in parasitology.

[17]  P. Newton,et al.  Mixed-species malaria infections in humans. , 2004, Trends in parasitology.

[18]  D. Conway,et al.  A large focus of naturally acquired Plasmodium knowlesi infections in human beings , 2004, The Lancet.

[19]  Guofa Zhou,et al.  Genetic diversity and multiple infections of Plasmodium vivax malaria in Western Thailand. , 2003, The American journal of tropical medicine and hygiene.

[20]  A. Kaneko,et al.  Mosaic organization and heterogeneity in frequency of allelic recombination of the Plasmodium vivax merozoite surface protein-1 locus , 2002, Proceedings of the National Academy of Sciences of the United States of America.

[21]  Y. Samung,et al.  Potential for Anopheles campestris (Diptera: Culicidae) to Transmit Malaria Parasites in Pa Rai Subdistrict (Aranyaprathet, Sa Kaeo Province), Thailand , 2002, Journal of medical entomology.

[22]  G. Snounou,et al.  Cryptic Plasmodium falciparum parasites in clinical P. vivax blood samples from Thailand. , 2002, Transactions of the Royal Society of Tropical Medicine and Hygiene.

[23]  S. Looareesuwan,et al.  Primaquine-tolerant vivax malaria in Thailand. , 1997, Annals of tropical medicine and parasitology.

[24]  J. Thompson,et al.  The CLUSTAL_X windows interface: flexible strategies for multiple sequence alignment aided by quality analysis tools. , 1997, Nucleic acids research.

[25]  J. Lines,et al.  Entomological evaluation of community-wide use of lambdacyhalothrin-impregnated bed nets against malaria in a border area of north-west Thailand. , 1995, Transactions of the Royal Society of Tropical Medicine and Hygiene.

[26]  J. Fooden.  Systematic review of Southeast Asian longtail macaques, Macaca fascicularis (Raffles, [1821]) / Jack Fooden. , 1995 .

[27]  J. Lines,et al.  Susceptibility of Thai zoophilic Anophelines and suspected malaria vectors to local strains of human malaria parasites. , 1994, The Southeast Asian journal of tropical medicine and public health.

[28]  T. McCutchan,et al.  Evolutionary relatedness of some primate models of Plasmodium. , 1993, Molecular biology and evolution.

[29]  S. Malikul.  The current situation of the anti-malaria programme in Thailand. , 1988, The Southeast Asian journal of tropical medicine and public health.

[30]  S. Looareesuwan,et al.  HIGH RATE OF PLASMODIUM VIVAX RELAPSE FOLLOWING TREATMENT OF FALCIPARUM MALARIA IN THAILAND , 1987, The Lancet.

[31]  Krotoski Wa.  Frequency of relapse and primaquine resistance in Southeast Asian vivax malaria. , 1980 .

[32]  W. A. Krotoski.  Frequency of relapse and primaquine resistance in Southeast Asian vivax malaria. , 1980, The New England journal of medicine.

[33]  T. Harinasuta,et al.  Relapses of vivax malaria after a conventional course of primaquine and chloroquine: report of 2 cases. , 1973, The Southeast Asian journal of tropical medicine and public health.