Al-Mekhlafi Abdulsalam Mq, Mahdy Mohammed Ak, A Azazy Ahmed, Fong Mun Yik
Department of Parasitology, Faculty of Medicine, University of Malaya, 50603 Kuala Lumpur, Malaysia.
Parasit Vectors. 2010 Nov 19;3:110. doi: 10.1186/1756-3305-3-110.
Malaria is an endemic disease in Yemen and is responsible for 4.9 deaths per 100,000 population per year and 43,000 disability adjusted life years lost. Although malaria in Yemen is caused mainly by Plasmodium falciparum and Plasmodium vivax, there are no sequence data available on the two species. This study was conducted to investigate the distribution of the Plasmodium species based on the molecular detection and to study the molecular phylogeny of these parasites.
Blood samples from 511 febrile patients were collected and a partial region of the 18 s ribosomal RNA (18 s rRNA) gene was amplified using nested PCR. From the 86 positive blood samples, 13 Plasmodium falciparum and 4 Plasmodium vivax were selected and underwent cloning and, subsequently, sequencing and the sequences were subjected to phylogenetic analysis using the neighbor-joining and maximum parsimony methods.
Malaria was detected by PCR in 86 samples (16.8%). The majority of the single infections were caused by P. falciparum (80.3%), followed by P. vivax (5.8%). Mixed infection rates of P. falciparum + P. vivax and P. falciparum + P. malariae were 11.6% and 2.3%, respectively. All P. falciparum isolates were grouped with the strain 3D7, while P. vivax isolates were grouped with the strain Salvador1. Phylogenetic trees based on 18 s rRNA placed the P. falciparum isolates into three sub-clusters and P. vivax into one cluster. Sequence alignment analysis showed 5-14.8% SNP in the partial sequences of the 18 s rRNA of P. falciparum.
Although P. falciparum is predominant, P. vivax, P. malariae and mixed infections are more prevalent than has been revealed by microscopy. This overlooked distribution should be considered by malaria control strategy makers. The genetic polymorphisms warrant further investigation.
疟疾是也门的一种地方病，每年每10万人口中有4.9人死亡，造成43000个伤残调整生命年的损失。虽然也门的疟疾主要由恶性疟原虫和间日疟原虫引起，但尚无这两种疟原虫的序列数据。本研究旨在通过分子检测调查疟原虫种类的分布，并研究这些寄生虫的分子系统发育。
收集511例发热患者的血样，采用巢式PCR扩增18s核糖体RNA（18s rRNA）基因的部分区域。从86份阳性血样中，选取13份恶性疟原虫和4份间日疟原虫进行克隆，随后进行测序，并使用邻接法和最大简约法对序列进行系统发育分析。
通过PCR在86份样本（16.8%）中检测到疟疾。大多数单一感染由恶性疟原虫引起（80.3%），其次是间日疟原虫（5.8%）。恶性疟原虫+间日疟原虫和恶性疟原虫+三日疟原虫的混合感染率分别为11.6%和2.3%。所有恶性疟原虫分离株均与3D7菌株聚类，而间日疟原虫分离株与Salvador1菌株聚类。基于18s rRNA的系统发育树将恶性疟原虫分离株分为三个亚簇，间日疟原虫分为一个簇。序列比对分析显示，恶性疟原虫18s rRNA部分序列中的单核苷酸多态性为5%-14.8%。
虽然恶性疟原虫占主导地位，但间日疟原虫、三日疟原虫和混合感染比显微镜检查所显示的更为普遍。疟疾控制策略制定者应考虑到这种被忽视的分布情况。基因多态性值得进一步研究。
