The genetic diversity of Plasmodium falciparum infections in human is associated with the pathogenesis of malaria. It is commonly determined through amplification of the polymorphic regions of the merozoite surface proteins -1 (msp-1) and -2 (msp-2) genes. This study aimed to (1) determine the prevalence of the msp-1 and msp-2 allelic familiesand (2) identify the multiplicity of infection (MOI) in P. falciparum field isolates from the Jazan region in the Kingdom of Saudi Arabia (KSA). Blood samples from patients with microscopically confirmed malaria infections (N = 48), collected in 2010, were analysed for msp-1 and msp-2 polymorphisms.K1, MAD20 and RO33 allelic types of the msp-1 gene and 3D7 and FC27 alleles of the msp-2 gene were analysed via nested polymerase chain reaction (PCR) according to band size. The MOI was then calculated. In msp-1, 16 different alleles were identified by examining size differences in the agarose gels.
These alleles-representing 5, 5 & 6 alleles-belong to K1 (120bp-420bp), RO22 (180bp-420bp) and MAD 20 (150 bp-410bp), respectively. For msp-2, a larger range of amplicon sizes was detected. A total of 13 different alleles were identified: the FC27 family had 6 alleles (380- bp1280bp), while the 3D7 family had 7 alleles (110 bp-1200bp.MOI was 1.81 for MSP-1 & 2.17 for MSP-2, with overall mean MOI of 1.99). Considerable genetic diversity was evident in the P. falciparum field isolates from the Jazan region of KSA. This diversity represents an essential step in developing effective measures to prevent malaria in KSA, as well as in assessing vaccines derived from these genes.