Characterization of markers of chloroquine resistance in plasmodium falciparum among pregnant women in Oyo State: Any hope of chloroquine resistance reversal?

Background: Chloroquine (CQ) which is one of the 4-aminoquinolines was once the mainstay of malaria treatment before it was officially withdrawn due to widespread resistance to it by Plasmodium species. It is one of the cheapest, safest, easily produced antimalarial compounds and has one of the longest half-lives among the antimalarial drugs which are also safe for use in pregnancy. Reversal of CQ resistance back to sensitivity has been documented after a period of withdrawal, and this may be a great relief in achievement of effective antimalarial chemotherapy at a relatively cheaper cost in Nigeria. This study investigated the characterization of markers of CQ resistance in Plasmodium falciparum infection among pregnant women in Oyo State following several years of official CQ withdrawal for treatment in Nigeria. Materials and Methods: Thick and thin blood films were made from venous blood collected from 316 consenting pregnant women and dispensed into ethylenediaminetetraacetic acid bottles after initial screening with SD Bioline RDT kit. The blood films were processed for malaria microscopy using 10% Giemsa stain. Dry blood spots on Whatman no. 1 filter paper were used for parasite DNA extraction and subsequent detection of CQ resistance markers using restriction fragment length polymorphism. Results: Eighty-two out of the 316 samples were positive for P. falciparum and subjected to molecular analysis for the detection of Pfcrt and Pfmdr1 mutant genes. Out of the 82 positive cases, 75 and 80 expressed mutant Pfcrt and Pfmdr1 genes, respectively, while 73 expressed both Pfcrt and Pfmdr1 genes. Conclusion: The high prevalence of the two major molecular markers of CQ resistance in this study, portends a concern in achieving resurgence of sensitivity after years of official withdrawal, thus official malaria management protocols should be strictly adhered to by ensuring testing before drug use while also avoiding self-medication.