Molecular detection of chloroquine resistance in Plasmodium vivax isolates from North India: Analysis of single nucleotide polymorphisms in pvmdr1 gene.

OBJECTIVES

Plasmodium vivax remains a major cause of malaria in India, with chloroquine still used as first-line therapy. However, molecular data on resistance markers are limited. This study aimed to detect mutations in the pvmdr1 gene of P. vivax isolates and to assess their potential role as markers of chloroquine resistance.

METHODS

A total of 7530 patients with acute undifferentiated febrile illness were screened. Blood samples were examined using microscopy, rapid diagnostic tests, and PCR. Isolates positive for P. vivax mono-infection were subjected to PCR for pvmdr1 amplification followed by Sanger sequencing. Global pvmdr1 sequences from GenBank were included for phylogenetic analysis.

RESULTS

Among 7530 patients, 75 (0.99%) were confirmed as P. vivax malaria. The mean age was 29.2 years, with a male-to-female ratio of 2:1. Fever with chills was present in all cases, while neurological symptoms (6.6%), jaundice (6.6%), and haematological abnormalities (10.6%) were less frequent. Of the 75 isolates, 36 were successfully sequenced. M908L and F1076L were present in 100% of isolates, while T898A was detected in 5.6%. Phylogenetic analysis showed clustering of Indian isolates with haplotypes from Madagascar and Afghanistan, whereas Brazilian haplotypes formed a distinct branch.

CONCLUSIONS

This study detected the presence of pvmdr1 polymorphisms in P. vivax isolates from North India. Although M908L and F1076L mutations were fixed in all isolates, their role in clinical chloroquine resistance remains uncertain, particularly in the absence of Y976F. Continuous molecular surveillance, combined with therapeutic efficacy studies, is essential to monitor emerging resistance and guide malaria treatment policies.