Molecular surveillance of anti-malarial drug resistance genes in Plasmodium falciparum isolates in Odisha, India.

backgroundDespite significant progress in eliminating malaria from the state of Odisha, India, the disease is still considered endemic. Artesunate plus sulfadoxine-pyrimethamine (AS + SP) has been introduced since 2010 as first-line treatment for uncomplicated Plasmodium falciparum malaria. This study aimed to investigate the prevalence of mutations associated with resistance to chloroquine (CQ), sulfadoxine-pyrimethamine (SP), and artesunate (ART) in P. falciparum parasites circulating in the state.

methodsA total of 239 isolates of P. falciparum mono infection were collected during July 2018-November 2020 from the four different geographical regions of the state. Genomic DNA was extracted from 200 µL of venous blood and amplified using nested polymerase chain reaction. Mutations on gene associated with CQ (Pfcrt and Pfmdr1) were assessed by PCR amplification and restriction fragment length polymorphism, artemisinin (Pfk13) gene by DNA sequencing and SP (Pfdhfr and Pfdhps) genes by allele-specific polymerase chain reaction (AsPCR).

resultsThe point mutation in Pfcrt (K76T) was detected 2.1%, in Pfmdr1 (N86Y) 3.4%, and no mutations were found in Pfkelch13 propeller domain. Prevalence of Pfdhfr, Pfdhps and Pfhdfr-Pfdhps (two locus) gene mutations were 50.43%, 47.05% and 49.79% respectively. The single, double, triple and quadruple point mutations in Pfdhfr gene was 11.2%, 8.2%, 17.2% and 3.4% while, in Pfdhps gene was 10.9%,19.5%, 9.5% and 2.7% respectively. Of the total 13 haplotypes found in Pfdhfr, 8 were detected for the first time in the state and of the total 26 haplotypes found in Pfdhps, 7 were detected for the fisrt time in the state. The linked quintuple mutation Pfdhfr (N51I-C59R-S108N)-Pfdhps (A437G-K540E) responsible for clinical failure (RIII level of resistance) of SP resistance and A16V-S108T mutation in Pfdhfr responsible for cycloguanil was absent.

conclusionThe study has demonstrated a low prevalence of CQ resistance alleles in the study area. Despite the absence of the Pfkelch13 mutations, high prevalence of Pfdhfr and Pfdhps point mutations undermine the efficacy of SP partner drug, thereby threatening the P. falciparum malaria treatment policy. Therefore, continuous molecular and in vivo monitoring of ACT efficacy is warranted in Odisha.