Oladipo Oladosu O, Wellington Oyibo A, Sutherland Colin J
ANDI Centre of Excellence for Malaria Diagnosis/WHO-FIND Malaria Specimen Collection Site, College of Medicine, University of Lagos, P.M.B 12003, Idiaraba, Lagos, Nigeria.
Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, UK.
Diagn Pathol. 2015 Apr 28;10:41. doi: 10.1186/s13000-015-0276-2.
In Nigeria, despite the change in National malaria drug policy to artemisinin combination therapy (ACT) in 2005 due to widespread chloroquine resistance, chloroquine (CQ) is still widely used in the treatment of malaria because it is cheap, affordable and accessible. The use of ACT for the management of uncomplicated malaria is currently being promoted. The employment of genetic markers to track circulating chloroquine-resistant parasites are useful in elucidating likely poor efficacy of chloroquine, especially in settings where it is not recommended for the treatment of uncomplicated falciparum malaria. This study determined the prevalence of pfcrt haplotypes and point mutations in pfmdr1 genes four years after the change in antimalarial treatment policy from CQ to the ACTs in Lagos, a commercial city in South-West, Nigeria.
This was a cross sectional study on uncomplicated malaria in children less than 12 years that presented with fever and other symptoms suggestive of malaria. Parasite DNA was extracted from 119 patients out of 251 children who were positive for Plasmodium falciparum by microscopy and amplified. The occurrence of haplotypes was investigated in pfcrt gene using probe-based qPCR and single nucleotide polymorphisms in pfmdr1 gene using nested PCR.
One hundred and nine (109) of the 119 children with P falciparum infection (91.6%) harbourd parasites with the mutant pfcrt haplotype (CVIET). Out of this, 4.2% comprised a mixture of genotypes encoding CVMNK and CVIET, while 4.2% had the wild type (CVMNK). Furthermore, the frequency of point mutations in pfmdr1 was 62.2% and 69.0% for codons Y86 and F184 respectively. There were no mutations at codons 1034, 1042 and 1246 of the Pfmdr1 genes.
The high frequency of the CQ-resistant haplotypes (CVIET) and mutations in Pfmdr1 associated with CQ resistance in P. falciparum among these children suggest that CQ-resistant parasites are still in circulation. Continuous use of chloroquine may continue to increase the level of mutations in pfcrt and pfmdr1genes. There is need to strengthen current case management efforts at promoting ACT use as well as urgently restricting access to chloroquine by the National drug regulatory agency, National Agency for Food Drug Administration and Control (NAFDAC).
The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/2069472010142303.
在尼日利亚，尽管由于氯喹广泛耐药，2005年国家疟疾药物政策已改为青蒿素联合疗法（ACT），但氯喹因其价格便宜、可负担且易于获取，仍被广泛用于疟疾治疗。目前正在推广使用ACT来治疗非复杂性疟疾。利用基因标记追踪循环中的氯喹耐药寄生虫，有助于阐明氯喹可能疗效不佳的原因，尤其是在不建议使用氯喹治疗非复杂性恶性疟的地区。本研究在尼日利亚西南部的商业城市拉各斯，对抗疟疾治疗政策从氯喹改为ACT四年后，测定了pfcrt单倍型的流行率以及pfmdr1基因中的点突变情况。
这是一项针对12岁以下出现发热及其他提示疟疾症状的非复杂性疟疾儿童的横断面研究。从251名经显微镜检查确诊为恶性疟原虫阳性的儿童中，选取119名患者提取其寄生虫DNA并进行扩增。使用基于探针的定量聚合酶链反应（qPCR）研究pfcrt基因中的单倍型出现情况，使用巢式聚合酶链反应研究pfmdr1基因中的单核苷酸多态性。
119名感染恶性疟原虫的儿童中，有109名（91.6%）携带突变型pfcrt单倍型（CVIET）的寄生虫。其中，4.2%为编码CVMNK和CVIET的基因型混合物，4.2%为野生型（CVMNK）。此外，pfmdr1中密码子Y86和F184的点突变频率分别为62.2%和69.0%。Pfmdr1基因的密码子1034、1042和1246未发生突变。
这些儿童中恶性疟原虫对氯喹耐药的单倍型（CVIET）频率较高，且Pfmdr1中的突变与氯喹耐药相关，这表明对氯喹耐药的寄生虫仍在传播。持续使用氯喹可能会继续增加pfcrt和pfmdr1基因的突变水平。有必要加强当前的病例管理工作，以推广ACT的使用，并由国家药品监管机构——国家食品药品监督管理局（NAFDAC）紧急限制氯喹的获取。
本文的虚拟切片可在此处找到：http://www.diagnosticpathology.diagnomx.eu/vs/2069472010142303。
