Use of the Plasmodium vivax merozoite surface protein 1 gene sequence analysis in the investigation of an introduced malaria case in Italy

Malaria due to Plasmodium vivax is globally widespread and is associated with substantial morbidity. The parasite was previously prevalent in temperate areas from which it has been eradicated, however there is a risk of re-introduction because of increased international travel and migration. Following the occurrence of an autochthonous case of P. vivax malaria in Italy after decades of malaria eradication, we applied a molecular approach to compare parasites involved in the introduced case and to determine whether a highly polymorphic gene marker could be useful to tag a P. vivax isolate geographically. To this end, the sequence encompassing the interspecies conserved blocks 5 and 6 of the gene encoding for merozoite surface protein 1 (msp-1) was determined in 16 P. vivax isolates from different regions, and analysed along with 24 pvmsp-1 sequences downloaded from published data. Results have shown that: (i) parasites from the introduced case and the putative source of infection identified following epidemiological investigation, although very similar, differed in three nucleotide substitutions, of which one non synonymous; ii) some geographical isolates looked tightly clustered (e.g. Korean and Punjab isolates), but others were less so.