Impact of chloroquine drug withdrawal on resistance of local Plasmodium falciparum malaria parasites to the drug in Tiwi and Mbita Towns of Kenya

Abstract

Chloroquine (CQ) drug was replaced in 1998 by Sulfadoxine - Pyrimethamine (SP) and later Artemisinin Based Combination therapy (ACT) as a first-line treatment of uncomplicated malaria in Kenya. This was due to development of resistance to CQ in Plasmodium falciparum Welch, 1897 malaria parasite. This study set out to determine the prevalence of the CQ resistance in malaria endemic Tiwi and Mbita towns of Kenya. Blood sample were collected from out-patient candidates with uncomplicated malaria using finger pricking techniques and spotted on filter paper Plasmodium falciparum were collected in blood samples drawn from naturally infected patients with uncomplicated malaria, visiting out-patient clinics in Tiwi (n=152) and Mbita (n=38) towns of Kenya in 1999 and 2008 or 2009. DNA extracted from individual spots in the paper were screened by nested PCR for presence of P. falciparum specific Chloroquine resistance markers using chloroquine resistance transporter (Pfcrt) and multi drug resistance (Pfmdr1) primers. Mutations and/or haplotypes in the Pfcrt and Pfmdr1 markers in the samples were assessed using dot blot hybridization technique. Temporal changes in the prevalence of the resistance were determined using Chi Square. There was significant reduction in prevalence of Pfmdr1-N86Y (P = 0.0009) and Pfcrt K76T (P = 0.0001) mutations in Tiwi between 1999 and 2008. Pfmdr1-N86Y and Pfcrt K76T mutations reduced to 63.6 and 56.9% respectively. In Mbita, change in prevalence of Pfmdr1-N86Y mutations between 1999 and 2009 was not significant (P = 0.7826), reducing to 84.2%, while Mbita’s prevalence of Pfcrt K76T mutation as at 2009 was 63.2%. There was a significant association in prevalence of P. falciparum between Tiwi 1999/Tiwi 2008 (χ2 df =1 = 10.958, P = 0.0009) and Mbita 2009/Tiwi 2008 (χ2 df =1 = 4.231, P = 0.00397). There was however no significant association in prevalence of P. falciparum between Tiwi 1999/Mbita 2009 (χ2 df =1 = 0.0715, P = 0.7891). Significant reduction in Pfmdr1-N86Y and Pfcrt K76T mutations in Tiwi, and not in Mbita suggest potential reduction in resistance to CQ in P. falciparum populations in Tiwi, but not Mbita. This indicates that CQ is still not a viable alternative to current antimalarial chemotherapy but can potentially be introduced as a combination therapy to treat and manage P. falciparum malaria in Tiwi, however, not in Mbita