Malele Imna, Craske Lisa, Knight Claire, Ferris Vanessa, Njiru Zablon, Hamilton Patrick, Lehane Stella, Lehane Mike, Gibson Wendy
Tsetse & Trypanosomiasis Research Institute, PO Box 1026, Tanga, Tanzania.
Infect Genet Evol. 2003 Nov;3(4):271-9. doi: 10.1016/s1567-1348(03)00090-x.
The accurate identification of trypanosome species and subspecies remains a challenging task in the epidemiology of human and animal trypanosomiasis in tropical Africa. Currently, there are specific PCR tests to identify about 10 different species, subspecies or subgroups of African tsetse-transmitted trypanosomes. These PCR tests have been used here to identify trypanosomes in four species of tsetse (Glossina brevipalpis, G. pallidipes, G. swynnertoni, G. morsitans morsitans) from two areas of Tanzania. PCR using species-specific primers was performed on 1041 dissection-positive proboscides, giving an overall positive identification in 254 (24%). Of these, 61 proboscides (24%) contained two or more trypanosomes. The trypanosome with the greatest overall prevalence at both field sites was Trypanosoma simiae Tsavo, which was identified in a total of 118 infected tsetse proboscides (46%). At Pangani, T. godfreyi was found in G. pallidipes but not in G. brevipalpis, suggesting that these flies might have different susceptibility to this trypanosome or might have fed on a different range of hosts. A high proportion (about 75%) of trypanosome infections remained unidentified. To investigate the identity of these unidentified samples, we used primers complementary to the conserved regions of trypanosomal small subunit ribosomal RNA (ssu rRNA) genes to amplify variable segments of the gene. Amplified DNA fragments were cloned, sequenced and compared with ssu rRNA genes on database of known trypanosome species. In this way, we have tentatively identified two new trypanosomes: a trypanosome related to Trypanosoma vivax and a trypanosome related to T. godfreyi. The T. godfreyi-related trypanosome occurred frequently in the Tanzanian field samples and appears to be widespread. Molecular identification of these two new trypanosomes should now facilitate their isolation and full biological characterisation.
在热带非洲人类和动物锥虫病的流行病学中，准确鉴定锥虫的种类和亚种仍然是一项具有挑战性的任务。目前，有特定的PCR检测方法可用于鉴定约10种不同的非洲采采蝇传播的锥虫种类、亚种或亚群。本文使用这些PCR检测方法来鉴定来自坦桑尼亚两个地区的四种采采蝇（短须舌蝇、淡足舌蝇、斯氏舌蝇、 morsitans morsitans舌蝇）中的锥虫。使用物种特异性引物对1041个解剖阳性的喙进行PCR检测，共得到254个（24%）阳性鉴定结果。其中，61个喙（24%）含有两种或更多种锥虫。在两个野外地点总体患病率最高的锥虫是塔氏锥虫Tsavo，在总共118个受感染的采采蝇喙中被鉴定出来（46%）。在潘加尼，在淡足舌蝇中发现了戈氏锥虫，但在短须舌蝇中未发现，这表明这些苍蝇对这种锥虫可能有不同的易感性，或者可能以不同范围的宿主为食。高比例（约75%）的锥虫感染仍未得到鉴定。为了研究这些未鉴定样本的身份，我们使用与锥虫小亚基核糖体RNA（ssu rRNA）基因保守区域互补的引物来扩增该基因的可变片段。将扩增的DNA片段进行克隆、测序，并与已知锥虫种类数据库中的ssu rRNA基因进行比较。通过这种方式，我们初步鉴定出两种新的锥虫：一种与间日锥虫相关的锥虫和一种与戈氏锥虫相关的锥虫。与戈氏锥虫相关的锥虫在坦桑尼亚的野外样本中频繁出现，似乎分布广泛。这两种新锥虫的分子鉴定现在应该有助于它们的分离和全面的生物学特性描述。
