Chloroquine-resistant Plasmodium falciparum (CRPF)
malaria isolates in Southeast Asia and sub-Saharan Africa share the same
Plasmodium falciparum chloroquine resistance transporter (PfCRT) haplotype (CVIET;
amino acids 72 to 76). It is believed that CRPF
malaria emerged in Southeast Asia and spread to sub-Saharan Africa via the Indian subcontinent. Based on this assumption, we hypothesized that CRPF isolates in India should possess the same drug resistance haplotype (PfCRT haplotype CVIET) as P. falciparum isolates in Southeast Asia and Africa and that the prevalence of CRPF may be higher and more widespread in India than appreciated. To test this postulate, we utilized a standardized real-time PCR assay to assess the prevalence and distribution of PfCRT haplotypes in P. falciparum isolates (n = 406) collected from Western, Central, and Eastern states in India and compared them to isolates from South America and Africa. Based on the proportion of isolates possessing the molecular marker K76T, the prevalence of
chloroquine resistance was high in all five regions of India studied (91%), as well as in Uganda (98%) and Suriname (100%). All isolates from Suriname contained the
chloroquine-resistant SVMNT haplotype typical of South American isolates, and 98% of isolates from Uganda possessed the
chloroquine-resistant CVIET haplotype characteristic of Southeast Asian/African strains. However, of 246 P. falciparum isolates from across India that contained the molecular marker for
chloroquine resistance, 81% contained the SVMNT haplotype. In conclusion, the prevalence of CRPF
malaria was high in geographically dispersed regions of India, and the primary haplotype observed, SVMNT, did not support a presumed geographic spread from contiguous Southeast Asia.