Plasmodium falciparum Chloroquine- pfcrt Resistant Haplotypes in Brazilian Endemic Areas Four Decades after CQ Withdrawn.

(1) Background: Malaria is a public health problem worldwide. Despite global efforts to control it, antimalarial drug resistance remains a great challenge. In 2009, our team identified, for the first time in Brazil, chloroquine (CQ)-susceptible parasites in isolates from the Brazilian Amazon. The present study extends those observations to include survey samples from 2010 to 2018 from the Amazonas and Acre states for the purpose of tracking molecular changes in parasites. (2) Objective: to investigate SNPs in the gene associated with chemoresistance to CQ ( (3) Methods: Sixty-six samples from the Amazonas and Acre states were collected from 2010 to 2018 in patients diagnosed at the Reference Research Center for Treatment and Diagnosis of Malaria (CPD-Mal/Fiocruz), FMT-HVD and Acre Health Units. These samples were subjected to PCR and DNA Sanger sequencing to identify mutations in (C72, M74, N75, and K76 (4) Results: Of the 66 samples genotyped for , 94% carried CQ-resistant genotypes and only 4 showed a CQ sensitive-wild type genotype, i.e., 1 from Barcelos and 3 from Manaus. (5) Conclusion: CQ-resistant populations are fixed, and thus, CQ cannot be reintroduced in malaria falciparum therapy.