Population genetic study of Plasmodium falciparum parasites pertaining to dhps gene sequence in malaria endemic areas of Assam.

ABSTRACT

Plasmodium falciparum malaria parasite had developed resistance to almost all the currently used antimalarial drugs. The purpose of the study was to come across the genetic distances in P. falciparum dhps gene sequences circulating in Assam. A partial fragment of P. falciparum dhps gene containing major single nucleotide polymorphisms associated with sulphadoxine resistance were amplified and sequenced. Thereafter specific bioinformatics tools like BioEdit v7.0.9, ClustalW in Mega 5, DnaSP version v.5.10.01 etc were used for the analysis. A total of 100 P. falciparum positive cases in different malaria endemic areas of Assam were included for the study. Based upon the mutation analysis, a total of seven different P. falciparum dhps genotypes were observed with five variable sites. Maximum five haplotypes were found in the P. falciparum isolates from Jorhat district of Assam. Four polymorphic sites were observed in the P. falciparum dhps gene sequences in Karbi Anglong, NC Hills, Chirang and Jorhat whereas the isolates from other study areas had three polymorphic sites. A statistically significant positive value of Tajima’s D were observed among the P. falciparum field isolates in Assam indicating that there is an excess of intermediate frequency alleles and can result from population bottlenecks, structure and/or balancing selection. Extensive gene flow took place among the P. falciparum population of Jorhat with Sivasagar, Chirang with Sivasagar and Chirang with Karbi Anglong. However, large genetic differentiation was observed among the P. falciparum isolates of NC Hills with Lakhimpur, Tinsukia, Dibrugarh and Golaghat and also the parasite population of Karbi Anglong with Lakhimpur and Tinsukia signifying little gene flow among the population. This finding has shown that mutant Pfdhps gene associated with sulphadoxine resistance is circulating in Assam. It is believed that, the parasite population may have undergone high level of breeding.