Department of Veterinary Tropical Diseases, University of Pretoria, Onderstepoort 0110, South Africa.
Vet Parasitol. 2010 Feb 10;167(2-4):123-35. doi: 10.1016/j.vetpar.2009.09.014. Epub 2009 Sep 19.
Ehrlichia ruminantium is an obligately intracellular proteobacterium which causes a disease known as heartwater or cowdriosis in some wild, and all domestic, ruminants. The organism is transmitted by ticks of the genus Amblyomma, and it is of serious economic importance wherever the natural vectors occur, an area which includes all of sub-Saharan Africa, and several islands in the Caribbean. The disease was first recognized in South Africa in the 19th century, where its tick-borne nature was determined in 1900, but the organism itself was not demonstrated until 1925, when it was recognized to be a rickettsia, initially named Rickettsia ruminantium. It was thus the first species of what are now known as Ehrlichia to be discovered, and most of the early work to elucidate the nature of the organisms, and its reservoirs and vectors, was performed in South Africa. The next milestone was the development, in 1945, of an infection and treatment regimen to immunize livestock, and this is still the only commercially available "vaccine" against the disease. Then in 1985, after fruitless attempts over many years, the organism was propagated reliably in tissue culture, opening the way for the first application of the newly developed techniques of molecular genetics. From 1990 onwards the pace of heartwater research accelerated rapidly, with notable advances in phylogeny, diagnosis, epidemiology, immunology, and vaccine development. The complete genome sequence was published in 2005, and during the last two years a new understanding has arisen of the remarkable genetic variability of the organism and new experimental vaccines have been developed. Despite all this the goal of producing an effective vaccine against the disease in the field still remains frustratingly just beyond reach. This article summarises our current understanding of the nature of E. ruminantium, at a time when the prospects for the development of an effective vaccine against the organism seem better than at any time since its discovery 83 years ago.
绵羊无形体是一种严格的细胞内细菌，可引起一些野生动物和所有家养反刍动物的疾病，称为心水病或牛蝇热。该病原体通过孤星蜱属的蜱传播，在其自然传播媒介存在的所有地区，包括撒哈拉以南非洲的所有地区和加勒比地区的几个岛屿，均具有严重的经济重要性。该疾病于 19 世纪在南非首次被发现，其蜱传性质于 1900 年确定，但直到 1925 年才证明该病原体本身的存在，当时它被确认为立克次体，最初名为绵羊无形体。因此，它是第一个被发现的现在被称为无形体的物种，而阐明该生物体及其宿主和传播媒介的性质的大部分早期工作都是在南非进行的。下一个里程碑是 1945 年开发了一种感染和治疗方案来免疫牲畜，这仍然是针对该疾病的唯一商业上可用的“疫苗”。然后，在 1985 年，经过多年的无果尝试后，该病原体在组织培养中可靠地繁殖，为首次应用新开发的分子遗传学技术开辟了道路。从 1990 年开始，心水病研究的步伐迅速加快，在系统发育、诊断、流行病学、免疫学和疫苗开发方面取得了显著进展。该病原体的完整基因组序列于 2005 年发布，在过去两年中，人们对该生物体惊人的遗传变异性有了新的认识，并开发了新的实验性疫苗。尽管取得了所有这些进展，但在野外生产针对该疾病的有效疫苗的目标仍然令人沮丧地遥不可及。本文总结了我们目前对绵羊无形体性质的理解，此时，开发针对该生物体的有效疫苗的前景似乎比 83 年前发现以来的任何时候都要好。
