Abstract
BackgroundAnti-malarial resistance is, and continues to be a significant challenge in the fight against malaria and a threat to achieving malaria elimination. In Zambia, chloroquine (CQ), a safe, affordable and well-tolerated drug, was removed from use in 2003 due to high levels of resistance evidenced with treatment failure. This study sought to investigate the prevalence of chloroquine resistance markers in Southern and Western Provinces of Zambia 14 years after the withdrawal of CQ.MethodsData from a cross-sectional, all-age household survey, conducted during the peak malaria transmission season (April–May 2017) was analysed. During the all-age survey, socio-demographic information and coverage of malaria interventions were collected. Consenting individuals were tested for malaria with a rapid diagnostic test and a spot of blood collected on filter paper to create a dried blood spot (DBS). Photo-induced electronic transfer–polymerase chain reaction (PET–PCR) was used to analyse the DBS for the presence of all four malaria species. Plasmodium falciparum positive samples were analysed by high resolution melt (HRM) PCR to detect the presence of genotypic markers of drug resistance in the P. falciparum chloroquine resistance transporter (Pfcrt) and P. falciparum multi-drug resistance (Pfmdr) genes.ResultsA total of 181 P. falciparum positive samples were examined for pfcrt K76T and MDR N86. Of the 181 samples 155 successfully amplified for Pfcrt and 145 for Pfmdr N86. The overall prevalence of CQ drug-resistant parasites was 1.9% (3/155), with no significant difference between the two provinces. No N86Y/F mutations in the Pfmdr gene were observed in any of the sample.ConclusionThis study reveals the return of CQ sensitive parasites in Southern and Western Provinces of Zambia 14 years after its withdrawal. Surveillance of molecular resistant markers for anti-malarials should be included in the Malaria Elimination Programme so that resistance is monitored country wide.
Highlights
Anti-malarial resistance is, and continues to be a significant challenge in the fight against malaria and a threat to achieving malaria elimination
Resistance to chloroquine (CQ) in P. falciparum parasites is predominantly linked to a single mutation in the P. falciparum transporter gene (Pfcrt) on chromosome 7, which encodes a protein localized on the parasite digestive vacuole (DV) membrane
Prevalence of Pfcrt K76T and P. falciparum multi-drug resistance (Pfmdr) N86Y For Pfcrt, only 1 (0.6% 95% CI 0.02, 3.5) of the samples had the resistant allele with 2 (1.3% 95% CI 0.2, 4.6) samples having both resistant and sensitive alleles
Summary
Anti-malarial resistance is, and continues to be a significant challenge in the fight against malaria and a threat to achieving malaria elimination. In Zambia, chloroquine (CQ), a safe, affordable and well-tolerated drug, was removed from use in 2003 due to high levels of resistance evidenced with treatment failure. While the malaria map has been shrinking over the years, there are a number of challenges in maintaining control or progressing to elimination, that include: access to treatment for most at risk and hard to reach populations; insecticide resistance; residual or outdoor transmission and drug resistance, Sitali et al Malar J (2019) 18:391 the threat of resistance to artemisinin and artemisinin-based combination therapy [2]. CQ resistant (CQR) P. falciparum parasites survive by reducing the accumulation of CQ in the food digestive vacuole inhibiting haemozoin formation [6, 9]
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