Mans Ben J, Pienaar Ronel, Latif Abdalla A
Parasites, Vectors and Vector-Borne Diseases, Agricultural Research Council-Onderstepoort Veterinary Institute, Onderstepoort 0110, South Africa ; The Department of Veterinary Tropical Diseases, University of Pretoria, Pretoria, South Africa ; Department of Life and Consumer Sciences, University of South Africa, South Africa.
Parasites, Vectors and Vector-Borne Diseases, Agricultural Research Council-Onderstepoort Veterinary Institute, Onderstepoort 0110, South Africa.
Int J Parasitol Parasites Wildl. 2015 Jan 6;4(1):104-18. doi: 10.1016/j.ijppaw.2014.12.006. eCollection 2015 Apr.
An extensive range of serological and molecular diagnostic assays exist for most of the economically important Theileira species such as T. annulata, T. equi, T. lestoquardi, T. parva, T. uilenbergi and other more benign species. Diagnostics of Theileria is considered with regard to sensitivity and specificity of current molecular and serological assays and their use in epidemiology. In the case of serological assays, cross-reactivity of genetically closely related species reduces the use of the gold standard indirect fluorescent antibody test (IFAT). Development of antigen-specific assays does not necessarily address this problem, since closely related species will potentially have similar antigens. Even so, serological assays remain an important line of enquiry in epidemiological surveys. Molecular based assays have exploded in the last decade with significant improvements in sensitivity and specificity. In this review, the current interpretation of what constitute a species in Theileria and its impact on accurate molecular diagnostics is considered. Most molecular assays based on conventional or real-time PCR technology have proven to be on standard with regard to analytical sensitivity. However, consideration of the limits of detection in regard to total blood volume of an animal indicates that most assays may only detect >400,000 parasites/L blood. Even so, natural parasitaemia distribution in carrier-state animals seems to be above this limit of detection, suggesting that most molecular assays should be able to detect the majority of infected individuals under endemic conditions. The potential for false-negative results can, however, only be assessed within the biological context of the parasite within its vertebrate host, i.e. parasitaemia range in the carrier-state that will support infection of the vector and subsequent transmission.
对于大多数具有经济重要性的泰勒虫物种，如环形泰勒虫、马泰勒虫、莱氏泰勒虫、小泰勒虫、乌氏泰勒虫以及其他一些致病性较弱的物种，已有广泛的血清学和分子诊断检测方法。泰勒虫病的诊断需考虑当前分子和血清学检测方法的敏感性和特异性及其在流行病学中的应用。就血清学检测而言，遗传关系密切的物种之间的交叉反应性降低了金标准间接荧光抗体试验（IFAT）的应用价值。抗原特异性检测方法的开发不一定能解决这个问题，因为关系密切的物种可能会有相似的抗原。即便如此，血清学检测在流行病学调查中仍然是一条重要的研究途径。基于分子的检测方法在过去十年中迅猛发展，其敏感性和特异性有了显著提高。在这篇综述中，我们考虑了目前对泰勒虫物种构成的理解及其对准确分子诊断的影响。大多数基于常规或实时PCR技术的分子检测方法在分析敏感性方面已被证明符合标准。然而，考虑到动物全血体积的检测限表明，大多数检测方法可能只能检测到每升血液中超过400,000个寄生虫。即便如此，带虫状态动物的自然寄生虫血症分布似乎高于这个检测限，这表明大多数分子检测方法应该能够在地方流行条件下检测到大多数受感染个体。然而，假阴性结果的可能性只能在寄生虫在其脊椎动物宿主内的生物学背景下进行评估，即带虫状态下支持媒介感染和后续传播的寄生虫血症范围。
