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Background  In Iran, co-infections of  Plasmodium vivax  and  Plasmodium falciparum  are common and  P. vivax  infections are often exposed to sulphadoxine-pyrimethamine (SP). In the present study, the frequency distribution of mutations associated to SP resistance was investigated in  pvdhfr  and  pvdhps  genes from field isolates.    Methods  Clinical isolates of  P. vivax  were collected in two different malaria endemic regions in northern and south-eastern Iran, between 2001 and 2006. All 189 collected isolates were analysed for SNP/haplotypes at positions 13, 33, 57, 58, 61, 117 and 173 of the  pvdhfr  and 383 and 553 of  pvdhps  genes using nested PCR-RFLP methods    Results  All 189 examined isolates were found to carry wild-type amino acids at positions 13, 33, 61 and 173, while 57L and 58R and 117N mutations in pure form was detected among 1.1%, 17.5% and 26% examined samples, respectively, with no polymorphisms in different loci of  dhps  genes. Based on size polymorphism of  pvdhfr  genes at repeat region, among northern isolates, the frequency distribution for type A and B were 2.2% and 97.8% respectively. However, in southern samples the prevalence of type A, B and C were 7%, 89.5% and 7.7%, respectively. Mixed genotype infections (type B and C) were detected in only 4.2% (6/143) of southern, but in none of the northern isolates. The combination of  pvdhfr and pvdhps  haplotypes among all 189 samples demonstrated six distinct haplotypes. The two most prevalent haplotypes among all examined samples were I 13 P 33 F 57 S 58 T 61 S 117 I 173 /A 383 A 553  (65.6%) and I 13 P 33 F 57 S 58 T 61  N  117 I 173  (16.4%). Two other alleles with one point mutation I 13 P 33 F 57  R  58 T 61 S 117 I 173 /A 383 A 553  and two mutations I 13 P 33 F 57  R  58 T 61  N  117 I 173 /A 383 A 553  accounted for 7.4% and 9.5% of the total isolates.    Conclusion  The present molecular data provide important information for making decisions on population based drug use in Iran. In addition, since October 2005, with more availability of SP as first-line treatment,  P. vivax  isolates are more exposed to SP and the selection or spread of resistant  pvdhfr  and  pvdhps  alleles might increase in the near future in this region.

Molecular characterization of antifolates resistance-associated genes, (dhfr and dhps) in Plasmodium vivax isolates from the Middle East