Emerging Chlamydia-like organisms as novel causes of bovine reproductive failure

许多传染病影响牲畜，不仅影响动物的健康和福利，而且影响农业的经济可持续性和未来的粮食安全。牛的繁殖失败是农业部门非常关注的一个领域，因为它对英国牛群的生产力有重大影响。虽然有许多因素导致牲畜系统中的繁殖率降低，但感染起着关键作用，据报告，77%的牛胎儿死亡诊断病例是由感染原因造成的。然而，对牛产前死亡的传染性原因的诊断很差，80%的病例仍未得到诊断（根据DEFRA 2002- 2009年兽医调查监测报告）。这在一定程度上可以解释为未能检测到其他未查明的致病有机体的存在。近年来，在环境中发现的一组新出现的细菌生物体的鉴定有所增加，这些细菌生物体已被证明与人类的各种疾病有关，如肺炎和流产。这些生物与已知在人类和动物中引起广泛感染（如性传播感染、肺炎、失明和胎儿死亡）的衣原体物种具有相似的生物学特征，被称为衣原体样生物。这些衣原体样生物也日益被认为是牲畜的潜在致病生物，尤其与小牛的产前死亡有关。事实上，在英国超过四分之一的分析病例中发现了它们，因此可以解释DEFRA报告的80%未统计，未诊断病例中的一些。迄今为止，进行的唯一研究依赖于对组织样本的分析，这些样本已提交给兽医实验室进行疾病诊断。虽然这些研究对于证明样本中存在无法获得其他诊断的生物体至关重要，但它们只在相对较少的样本上进行了研究。此外，一般而言，关于动物起源农场的疾病和生产历史的信息很少。因此，本研究旨在调查这些生物在英国奶牛场的存在，以及它们与动物生产性能的关系。我们将从临床样本中分离出生物体，以使我们能够描述和评估英国牛群中存在多少种不同类型的衣原体样生物体，并通过分析环境样本（如饮用水和床上用品）来调查它们在动物之间传播的可能性。我们还将开发实验模型系统，使我们能够调查生物体如何引起感染和疾病，并确定对感染的免疫反应。这些研究的结合将大大增加我们对这组新兴细菌在牛繁殖中的致病潜力和作用的理解。研究结果将有助于改进对牛繁殖失败的诊断，使养殖业了解这些微生物的存在，改进管理系统，并允许对未来预防疾病发病率的疫苗战略的潜在效益进行评估。

Many infectious diseases affect livestock, impacting not only on the health and welfare of the animals but also on the economic sustainability of the agricultural industry and future food security. Reproductive failure in cattle is one area of great concern to the agricultural sector, as it has a major impact on productivity in UK cattle herds. While there are many factors contributing to reduced rates of reproduction in livestock systems, infection plays a key role, with 77% of diagnosed cases of bovine fetal death reported as resulting from infectious causes. However, diagnosis of the infectious causes of pre-natal death in cattle is poor, with 80% of cases remaining undiagnosed (according to DEFRA's Veterinary Investigation Surveillance reports for 2002-09). This can be explained in part by a failure to detect the presence of other unidentified disease causing organisms.In recent years, there has been an increase in the identification of a group of new emerging bacterial organisms that are found in the environment and have been shown to be associated with a variety of conditions in humans, such as pneumonia and miscarriage. These organisms, which share similar biological characteristics to Chlamydia species that are known to cause a broad range of infections in humans and animals, such as sexually-transmitted infections, pneumonia, blindness and fetal death, are referred to as Chlamydia-like organisms. These Chlamydia-like organisms are also increasingly becoming recognized as potential disease causing organisms of livestock, being particularly associated with the pre-natal death of calves. Indeed, they have been found in over a quarter of the cases analyzed in the UK, and thus could account for some of the 80% unaccounted, undiagnosed cases reported by DEFRA.To date, the only studies that have been carried out have relied upon the analysis of tissue samples, which have been submitted to veterinary laboratories for disease diagnosis. While these studies have been vital in demonstrating the presence of the organisms in samples for which no alternative diagnoses could be reached, they have been performed on a relatively small number of samples. In addition, in general, little information is obtained on the disease and production histories of the farms from which the animals originated. Thus, this study aims to investigate the presence of these organisms on dairy farms across the UK and how this relates to animal production performance. We will isolate the organisms from clinical samples to allow us to characterise and assess how many different types of Chlamydia-like organisms are present in the UK cattle herds, as well as investigate their potential spread from animal to animal by analyzing environmental samples, such as drinking water and bedding. We will also develop experimental model systems to allow us to investigate how the organisms cause infection and disease, and determine the immune response to infection.The combination of these studies will greatly increase our understanding of the disease causing potential and role of this group of emerging bacteria in cattle reproduction. The outcomes will lead to improved diagnoses of cattle reproductive failure, inform and educate the industry to the presence of these organisms, lead to improved management systems and allow an evaluation of the potential benefits of future vaccine strategies to prevent disease incidence.