Population genetics structure of Plasmodium vivax circumsporozoite protein during the elimination process in low and unstable malaria transmission areas, southeast of Iran

• Iranian P. vivax isolates from control and elimination phases were analyzed using CSP.
• No mixed infections (VK210/VK247) were detected among the elimination samples.
• Sequence lengths, SNPs, and In/Del polymorphisms showed low diversity.
• There was a turnover of P. vivax parasite genotypes due to cross border movement.
• Active surveillance for limiting reintroductions of new allelic forms should be considered.

In Iran, the prevalence of Plasmodium falciparum and Plasmodium vivax has dropped after a national malaria elimination program was launched. To estimate the likelihood of success and to measure the outcome of malaria intervention tools during elimination programs (2008–2012), the population genetic surveys of Iranian P. vivax isolates (n = 60) were carried out using the CSP genetic marker. The results were compared with a similar work that was carried out during a control phase (2000–2003) in the same study areas. Based on PCR-RFLP analysis, 49 (81.67%) of 60 studied samples were VK210 and 11 (18.33%) were VK247 with no mixed genotypes. However, 10.97% of P. vivax isolates of control phase harbored the mixed genotypes. Sequencing analysis of 50 pvcsp gene showed 14 distinct haplotypes, of which 11 and 3 were VK210 and VK247 types, respectively. However, during the control phase, 19 distinct subtypes (11 VK210 and 8 VK247) were reported. Also, 7 of 11 VK210 and the VK247F subtypes were new, and 3 out of 7 new VK210 and VK247F were isolated from the patients with Pakistani nationality. The lower nucleotide diversity per site (π = 0.02017 ± 0.00436 and π = 0.04525 ± 0.00255) and haplotype diversity (Hd = 0.513 ± 0.093 and Hd = 0.691 ± 0.128) as well as lower In/Del haplotype [Hd(i) = 0.243 and 0] and nucleotide diversity [π(i) = 0.00078 and 0] were recorded for VK210 and VK247of the elimination samples, respectively. In conclusion, the comparison of PRMs and RATs in CRR along with the polymorphism analysis of the sequence lengths, SNPs, and In/Del polymorphisms in all analyzed samples showed lower genetic diversity for PvCSP in the elimination samples. Also, although there is a turnover of P. vivax parasite genotypes in the study areas, reduction in genetic diversity and transmission was detected due to scaling-up of the intervention tools during an elimination program in Iran. This notable challenge of the elimination program must be taken into account and controlled by active surveillance for limiting both reintroductions of new allelic forms as well as the spread of drug-resistant parasite to prevent any disease outbreaks.

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