Date of Award

1-1-2017

Thesis Type

phd

Document Type

Thesis

Divisions

medic

Department

Faculty of Medicine

Institution

University of Malaya

Abstract

Yemen has updated its national malaria policies in 2009 to introduce histidine rich protein 2 – based rapid diagnostic test (HRP2-RDT) as a method of diagnosis in peripheral malaria-endemic areas, and to replace chloroquine (CQ) by artemisinin combination therapy (ACT) for treating uncomplicated falciparum malaria infection. The present study aimed to evaluate the HRP2-RDT and to assess the therapeutic efficacy of artesunate + sulfadoxine/pyrimethamine (AS+SP) as a first line treatment. A total of 622 febrile individuals from two malaria-endemic areas in Tehama region, Yemen (Hodeidah and Al-Mahwit governorates) were screened by CareStartTM malaria HRP2-RDT and confirmed later by microscopy, followed by gene sequencing analysis of Pfhrp2. Evaluation of AS+SP therapeutic efficacy was performed through in-vivo evaluation of the clinical and parasitological response over 28 days of follow-up according to standard protocols. Moreover, frequency of mutations associated with drugs resistance was obtained for the pfdhfr, pfdhps, and pfK13 genes for AS + SP, as well as pfcrt and pfmdr1 genes for other antimalarials. A total of 188 (30.2%) participants were found positive for P. falciparum by the RDT compared to 189 (30.4%) by microscopy. The sensitivity and specificity of the RDT were 90.5% and 96.1%, respectively. Eighty-six patients completed the AS+SP in-vivo study, with a cure rate of 96.5% (94.2% PCR-uncorrected). However, the efficacy of gametocyte clearance was poor, with gametocytes persisting throughout the study in some patients. All the isolates sequenced had the pfk13 propeller domain wild-type allele, and mutations associated with SP failure were observed only for pfdhfr, with the double mutation (S108N+N51I) was reported in 65.4% of the isolates. Pfcrt gene showed wide prevalence of mutations, with the predominance of pfcrt 76T CQ resistance (97.7%). Mutated pfcrt haplotypes were highly prevalent (98.8%) with CVIET classic, old-world African/Southeast Asian haplotype being the most predominant, and was mostly found in the isolates from Khamis Bani Saad and AdDahi districts (93.1% and 88.9% respectively). Interestingly, the SVMNT new-world South American haplotype was exclusively detected in isolates from Bajil districts of Hodeidah (9.3%). Mutations at Y184F of pfmdr1 were found at a fixation level (100%) in all districts, while mutations of codons 1034C and 86Y were only found in the isolates from AdDahi and Khamis Bani Saad districts. In conclusion, CareStartTM Malaria HRP2-based RDT showed high level of sensitivity and specificity in malaria-endemic areas in Yemen. Moreover, AS+SP therapy remains effective for the treatment of uncomplicated falciparum malaria iv with poor gametocidal activity. No polymorphism in pfk13 was detected in all isolates studied. Adding a single dose primaquine, which minimizes transmission potential, to the current ACT drug policy is strongly recommended. The high prevalence of mutations in pfcrt, 5 years after official cessation of CQ suggests a sustained CQ pressure on P. falciparum isolates in the study area. Moreover, the low prevalence of mutations in the pfmdr1 gene could be a good indicator of the high susceptibility of P. falciparum isolates to antimalarials other than CQ. Therefore, a new strategy to ensure the complete nationwide withdrawal of CQ from the private drug market is recommended.

Note

Thesis (PhD) - Faculty of Medicine, University of Malaya, 2017.

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