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GENETIC DIVERSITY OF PLASMODIUM VIVAX P_VCSP AND P_VMSP1 IN GUYANA, SOUTH AMERICA

Approximately 55% of malaria infections in the Guyana Amazon region are attributed to Plasmodium falciparum while the other 45% are attributed to non-falciparum, mostly Plasmodium vivax. However, little is known about the P. vivax strain types circulating in the region. Using PCR for Plasmodium detection and two genetic markers specific to P. vivax to detect the polymorphic circumsporozoite protein (CSP) and the conserved 19-kDa region of the merozoite surface protein-1 (MSP-1), we investigated the overall Plasmodium strain distribution and population diversity within P. vivax in isolates collected from the blood of infected individuals in the interior Amazon region of Guyana, South America. Out of a total of 250 samples positive for Plasmodium, P. vivax was detected in 30% (76/250) and P. falciparum was detected in 76% (189/250). Mixed infections containing both P. falciparum and P. vivax constituted 6% (15/250) of the total positive samples. Further analysis of P. vivax strains showed that 92% (56/61) of the P. vivax samples hybridized with a probe specific to type VK210, 39% (24/61) hybridized with a probe specific for type VK247, and 25% (15/61) hybridized with a probe specific for the P. vivax-like CS genotype. DNA sequencing of the 19-kDa C-terminal domain in block 13 of MSP-1 amplified from 61 samples from patients infected with P. vivax demonstrated that this region is highly conserved, and all samples were identical at the nucleotide level to the Belem and Salvador-1 types. No synonymous or nonsynonymous mutations were observed in this region of the gene, indicating that current vaccine-development efforts based on the MSP-1₁₉ fragment would be applicable in Guyana.

Received April 7, 2006. Accepted for publication July 20, 2006.

Acknowledgments: This work was partially supported by the Centers for Disease Control Cooperative Agreement (#U50/CCU016559-01) and an award from CDMHA (#6401-163-L-B). We thank the health care workers at the Ministry of Health clinics in Guyana, with special recognition and thanks to Dr. Jorge Garcia and Monica Pilgrim, and also the health care workers in Georgetown, Mahdia, and surrounding locales in the interior Amazon region, for all of their assistance with patient recruitment, sample collection, and logistical support.

^* Address correspondence to Carol J. Palmer, University of Florida, Department of Infectious Diseases and Pathology, P.O. Box 110880, 2015 SW 16th Ave., Gainesville, FL 32611-0880. E-mail: palmerc{at}mail.vetmed.ufl.edu, carpalmer{at}aol.com

Authors’ addresses: J. Alfredo Bonilla and Carol J. Palmer, Department of Infectious Diseases and Pathology, University of Florida, P.O. Box 110880, Gainesville, Florida 32611. Lloyd Validum, Department of Tropical Medicine, Woodlands Hospital, Georgetown, Guyana. Rudolph Cummings, Ministry of Health, Georgetown, Guyana.