Department of Veterinary Tropical Diseases, Faculty of Veterinary Science, University of Pretoria, Private Bag X4, Onderstepoort 0110, South Africa.
Vet Parasitol. 2010 Nov 24;174(1-2):145-9. doi: 10.1016/j.vetpar.2010.08.014. Epub 2010 Aug 21.
Seventy EDTA blood samples collected from plains zebra (Equus quagga burchellii) and Cape mountain zebra (Equus zebra zebra) were screened for the presence of piroplasm parasite DNA using quantitative T. equi-specific and B. caballi-specific TaqMan real-time PCR (qPCR) tests. T. equi parasite DNA was detected in 60 samples, 19 of which were also positive for B. caballi. Approximately 1480bp of the piroplasm 18S rRNA gene was amplified and sequenced from 17 samples, while the V4 hypervariable region of the 18S rRNA gene was amplified, cloned and sequenced from 31 samples. BLASTN analysis revealed that all of the sequences obtained were most similar to T. equi genotypes and not B. caballi genotypes. Although Babesia parasites were present in some of these samples, as indicated by qPCR, the parasitaemia may have been too low to allow detection by cloning of PCR products from a mixed infection. Sequence analyses of both the full-length and the V4 hypervariable region of the T. equi 18S rRNA gene revealed the existence of 13 new T. equi sequences from zebra, confirming the existence of sequence heterogeneity in the rRNA genes of the parasites that cause equine piroplasmosis, and further suggesting that there may be additional, as yet unidentified, T. equi and B. caballi 18S rRNA sequences present in the horse and zebra populations in South Africa. The occurrence of previously unrecognized sequence variation could pose a potential problem in the implementation of diagnostic tests targeting the 18S rRNA gene.
从平原斑马（Equus quagga burchellii）和海角山斑马（Equus zebra zebra）采集了 70 份 EDTA 血液样本，使用定量 T. equi 特异性和 B. caballi 特异性 TaqMan 实时 PCR（qPCR）检测方法筛选是否存在梨形虫寄生虫 DNA。在 60 个样本中检测到 T. equi 寄生虫 DNA，其中 19 个样本也为 B. caballi 阳性。从 17 个样本中扩增和测序了大约 1480bp 的梨形虫 18S rRNA 基因，从 31 个样本中扩增、克隆和测序了 18S rRNA 基因的 V4 高变区。BLASTN 分析表明，获得的所有序列与 T. equi 基因型最相似，而不是 B. caballi 基因型。尽管 qPCR 表明一些样本中存在巴贝斯虫寄生虫，但寄生虫血症可能太低，无法通过从混合感染的 PCR 产物中克隆来检测。T. equi 18S rRNA 基因全长和 V4 高变区的序列分析揭示了来自斑马的 13 种新的 T. equi 序列的存在，证实了引起马梨形虫病的寄生虫的 rRNA 基因存在序列异质性，并进一步表明在南非的马和斑马种群中可能存在其他尚未识别的 T. equi 和 B. caballi 18S rRNA 序列。针对 18S rRNA 基因实施的诊断检测中出现以前未识别的序列变异可能会带来潜在问题。
