Division of Veterinary Medicine, School of Veterinary Medicine and Science, The University of Nottingham, Sutton Bonington Campus, Loughborough, Leicestershire, LE12 5RD, UK.
Parasitol Res. 2010 Apr;106(5):1009-14. doi: 10.1007/s00436-010-1788-z. Epub 2010 Feb 18.
Neosporiosis, a serious disease caused by the apicomplexan intracellular parasite Neospora caninum, is considered to be one of the most economically important diseases in cattle. It is associated with potentially serious complications such as abortion, stillbirth and maternal infertility. To survive in fluctuating physiological and immunological environments, N. caninum has evolved a diverse set of regulatory mechanisms that govern various adaptive responses. The most intriguing paradigm in N. caninum adaptive evolutionary biology is its ability to alternate between two phenotypically and functionally distinct stages within the host. Recent research has reinforced the notion that N. caninum tachyzoite-bradyzoite stage switching on and off is correlated with its ability to form dormant cysts. Knowledge of the specific mechanisms that govern the dynamics of N. caninum phenotype switching enables a better understanding of the pathogenesis of the disease and effective control measures to be identified. Herein we review the available knowledge relating to various aspects of stage interconversion in N. caninum, with particular focus on the stress-related hypothesis presumed to be involved in this event. Finally, we put forward the postulation that N. caninum uses stage interconversion as an adaptive process to cope with the hostile environment within the host and to ensure its continuity in nature.
刚地弓形虫病是一种由顶复门内专性细胞内寄生的原虫刚地弓形虫引起的严重疾病，被认为是牛群中最重要的经济疾病之一。它与潜在的严重并发症有关，如流产、死产和母畜不孕。为了在波动的生理和免疫环境中生存，刚地弓形虫进化出了一套多样化的调节机制，这些机制控制着各种适应性反应。在刚地弓形虫适应性进化生物学中最引人注目的范例是它在宿主内能够在两种表型和功能明显不同的阶段之间交替。最近的研究加强了这样一种观点，即刚地弓形虫速殖子-缓殖子阶段的转换与它形成休眠包囊的能力有关。对控制刚地弓形虫表型转换动力学的特定机制的了解，使人们能够更好地理解疾病的发病机制，并确定有效的控制措施。本文综述了与刚地弓形虫各阶段相互转化相关的各种方面的现有知识，特别关注了与该事件相关的应激假说。最后，我们提出了一个假设，即刚地弓形虫利用阶段转换作为一种适应过程来应对宿主内恶劣的环境，并确保其在自然界中的连续性。
