Abstract: AIM: To explore the polymorphism of circumsporozoite protein (CSP) genes of different geographic strains of Plasmodium vivax and its significance. METHOD: PCR amplification and electrophoresis excised purification was used to obtain the studied DNA fragments. Dye primer cycle sequencing was used to sequence the CSP genes. A schematic diagram method was employed to compare and analyse the sequence deviation. RESULTS: All obtained CSP gene sequences of the 15 isolates from China, Philippines and Solomon Islands are P.vivax type-I in which some geographic deviations have been found. Six Chinese isolates were similar to NK isolate and one of them, C-2, was identical to NK isolate and remarkably distinct from all other type-I isolates. CONCLUSION: Based on the sequence deviation at amino acid level of CSP genes from different parts in the world and on Qarit's and Mann's grouping, all of type-I isolates published so far can be categorized into 2 families including 6 groups. The grouped sequence characteristics might be used to develop a rapid and practical method for the detection and identification of different geographic strains which could be of significance in malaria epidemiology and control, and be useful in the research of biology, taxonomy and phylogenetic of this parasite.

Key words: Plasmodium vivax, circumsporozoite pretein, DNA sequencing, polymorphism