Haplotypes of Chloroquine Resistance Marker Genes Among Uncomplicated Malaria Cases in Lagos, Nigeria.

Drug resistance resulting from mutations in Plasmodium falciparum, that caused the failure of previously effective malaria drugs, has continued to threaten the global malaria elimination goal. This study describes the profiles of P. falciparum chloroquine resistance transporter (Pfcrt) and P. falciparum multidrug resistance 1 (Pfmdr1), the genetic markers associated with 4-aminoquinoline resistance, among P. falciparum isolates from Lagos, Nigeria. Genomic DNA was extracted from the dried blood spot samples obtained from individuals with microscopically confirmed P. falciparum infection in health facilities and communities in Lagos State, Nigeria. The DNA was amplified using nested polymerase chain reaction, and sequence analysis was performed to identify single nucleotide polymorphisms in the pfcrt and pfmdr1 genes. The study showed that 82.4% (178) of the isolates had pfmdr1 wild-type, while mutations were observed at codons N86Y (11.6%) and D1246Y (3.2%). Other mutations seen were at codons Y23S (0.5%), E130K (2.3%), and S149P (0.5%). 30.8% (64) of the isolates had pfcrt wild-type (CVMNK), while 62.0% (129) had CVIET (mutant) haplotype. Other pfcrt haplotypes detected include; CVIDT (1.9%); CVMDT (1.4%); CVIKT (1.0%); CVINT (0.5%); CVMET (0.5%); CVMKT (0.5%); CVMNT (1.0%); and CVMEK (0.5%). The findings underscore the presence of uncommon pfcrt haplotypes and a high prevalence of drug-resistant pfcrt haplotypes (CVIET), alongside a high prevalence of wild-type pfmdr in Lagos. This study highlights the need for ongoing surveillance of these genetic markers to provide data that can inform decisions on malaria case management and preserve the efficacy of artemisinin combination therapies (ACTs) in Nigeria.