Email updates

Keep up to date with the latest news and content from Malaria Journal and BioMed Central.

Open Access Research

High prevalence of pfcrt-CVIET haplotype in isolates from asymptomatic and symptomatic patients in south-central Oromia, Ethiopia

Lemu Golassa12*, Nizar Enweji3, Berhanu Erko1, Abraham Aseffa2 and Göte Swedberg3

Author Affiliations

1 Aklilu Lemma Institute of Pathobiology, Addis Ababa University, Addis Ababa, Ethiopia

2 Armauer Hansen Research Institute, Addis Ababa, Ethiopia

3 Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden

For all author emails, please log on.

Malaria Journal 2014, 13:120  doi:10.1186/1475-2875-13-120

Published: 27 March 2014

Abstract

Background

As a result of extensive chloroquine resistance (CQR) in Plasmodium falciparum in late 1990s, Ethiopia replaced CQ with sulphadoxine-pyrimethamine (SP) as first-line drug, which in turn was replaced by artemisinin combination therapy in 2004. Plasmodium falciparum resistance to CQ is determined by the mutation at K76T of the P. falciparum chloroquine resistance transporter (pfcrt) gene. Understanding diversity in the P. falciparum genome is crucial since it has the potential to influence important phenotypes of the parasite such as drug resistance. Limited data is available regarding the type of pfcrt mutant allelic type, the effect of CQ withdrawal and diversity of the parasite population in south-central Oromia, Ethiopia.

Methods

Finger-pricked blood spotted on Whatman 3MM filter papers were collected from falciparum malaria patients. Parasite DNA was extracted from individual blood spots on the filter papers. The presence of K76T mutations was determined using nested PCR for all isolates. Complete sequencing of mutations in pfcrt 72-76 was done for a set of randomly selected resistant isolates. Four microsatellite (MS) markers were analysed to determine the heterozygosity.

Results

Although CQ was withdrawn for more than a decade, 100% of the parasites still carried the pfcrt K76T mutation. All isolates were mutant at the K76T polymorphism. Based on combinations of MS markers, seven different Ethiopian CQR variants (E1-E7) were identified. Heterozygosity (He) for MS flanking the pfcrt chloroquine resistance allele ranged from 0.00 (mscrt -29, -29.268 kb) to 0.21 (mscrt -2, -2.814 kb). He ranged from 0.00 (msint 3, 0 kb) to 0.19 (msint 2, 0 kb) for MS within the pfcrt gene. Both intronic and MS flanking the pfcrt gene showed low levels of diversity.

Conclusion

pfcrt CQR allele seems to be fixed in the study area. Of the different haplotypes associated with CQR, only the CVIET genotype was identified. No reversal to the wild-type has occurred in Ethiopia unlike in many Africa countries where CQR parasites declined after cessation of CQ use. Decreased diversity in CQR isolates surrounding pfcrt suggests CQ selection and homogenization among CQR parasite population. While mutation in msint 3 and mscrt -29 of the mutant pfcrt allele is being fixed, it seems that mutations in msint 2 and mscrt -2 are still evolving and may indicate the start of re-diversification of the population from a fixed 76 T population.

Keywords:
pfcrt; Wild-type; Drug resistance; Chloroquine; Plasmodium falciparum; Mutations; Heterozygosity; Microsatellite; Ethiopia