**7.3 Route 3: south America**

Chloroquine resistance was recorded in the 1960s in Columbia and Venezuela in South America [68]. Chloroquine-resistant parasites later spread to malariaendemic regions in Brazil, Guyana in 1969, Suriname in 1972, Ecuador in 1976, Peru in 1980, and Bolivia in 1980 [68]. Two different CQ-resistant haplotypes are recorded in South America, which are the SVMNT and CVMET haplotypes with SVMNT haplotype being the most widely spread haplotype (**Figure 1b**) [1, 73]. This suggests that the SVMNT haplotype, originally found in Venezuela is responsible for the emergence of CQ-resistant isolates in South America [73, 80]. Recently, two other haplotypes; CVIET and CVMNT have been reported in Brazil and

#### **Figure 1.**

*Origins and geographical spread of CQ resistance. (A) Three different* pfcrt *mutants; the CVIET type, SVMNT type, and CVMNT type. Migration of the CVIET type from Southeast Asia to Africa is the most notable cause of CQ resistance in Africa. Capital letters are abbreviations of amino acids at positions 72–76 in pfcrt. Red-colored letters represent mutations. (B) Four different* pfcrt *mutants; CVMET type, SVMNT type, CVMNT type, s-SVNMT type originate from South America whiles CVIET type is imported from Southeast Asia. The v-S(agt)VMNT type has different bases at position 72 from the S(tct)VMNT type originated from Venezuela. Abbreviations are the same as in (A). Adapted from [68].*

Peru respectively [81]. The CVIET haplotype might have been imported in South America from Southeast Asia or Africa [68].

#### **7.4 Recovery of CQ resistance**

The high level of CQ resistance in Malawi resulted in the ban of CQ for malaria treatment in Malawi in 1993. Just after 5 to 7 years after the CQ withdrawal, CQ

#### P. falciparum *and Its Molecular Markers of Resistance to Antimalarial Drugs DOI: http://dx.doi.org/10.5772/intechopen.98372*

sensitivity was observed [82, 83]. A decrease in the *pfcrt* K67T, which was 17% in 1998 and 2% in 2000 was observed [82]. Recovery of CQ resistance has been attributed to the expansion of wild-type *pfcrt* allele rather than a back mutation in the *pfcrt* allele [84]. This trend has also been recorded in Gabon, Vietnam [68], and China [85]. The rapid decrease in the CQ-resistance parasite population has been attributed to fitness costs incurred by the parasite as a result of the drug resistance [68].
