The Enterocytozoonidae: the emergence of a microsporidian clade into the aquatic and terrestrial food-chain

微孢子虫是一组被描述的1000多种寄生微生物，其物种感染所有环境中的所有主要动物谱系。微孢子虫的一个特别重要的家族是肠道细胞寄生虫科。这是一个耐人寻味的组织，其成员感染来自水生和陆地栖息地的宿主。它包括两个备受瞩目的成员：引起艾滋病相关腹泻的最常见原因之一的比内氏肠胞体菌和虎虾病原体肝细胞胞菌。后者与对虾生长严重迟缓有关，这给水产养殖业的数百万人造成了相当大的经济损失。此外，最近发现肝病原球虫跳过宿主，对食用白虾造成严重的疾病。鉴于其新出现的经济重要性，肠细胞虫科，特别是肝肠虫科，需要进一步研究，本奖学金旨在利用环境DNA来解决肠细胞虫科生物学中的以下两个问题：该奖学金的第一个目的是回答肝肠虫科是如何在亚洲的对虾养殖场传播的问题。虽然最初从泰国报道，但在中国、印度尼西亚、马来西亚、越南和印度也发现了肝肠炎。这种传播可能是通过受感染的对虾从一个养殖场转移到另一个养殖场，或者感染可能从中间宿主和/或受污染的饲料获得的。该项目建议使用分子数据来确定传播是如何发生的，从而为水产养殖政策提供信息，以防止进一步传播。最近拟议的项目合作伙伴之间的合作已经产生了肝炎型埃希氏菌的基因组序列数据，这些数据目前正被用于设计更好的诊断性聚合酶链式反应引物，以了解病原体的流行情况。该项目建议通过对从泰国多个地理位置、中国以及白虾和虎虾宿主收集的肝腺艾美耳球虫的基因组进行测序来扩大这项工作。产生的分子数据将用于重建菌株之间的进化关系，并推断地理位置和宿主之间的移动。第二个目标是解决环境中有多少未被发现的肠道寄生虫的问题。人类和虾是肠道细胞寄生虫科的两个重要宿主，两者都可能从尚未确定的中间宿主那里获得这些感染。该项目的这一组成部分旨在确定重要的肠细胞人畜共患病以及其他可能引起人类或动物疾病的物种的储藏者或携带者。我们将从人类和水生动物种群交界处的环境中收集无脊椎动物样本，例如生活污水、河流、河口和沿海栖息地，以及泰国的虾池。然后，我们将从所有这些生物及其相关寄生虫的DNA中提取DNA，并使用最先进的基因测序技术对样本中每种寄生虫的相同基因进行排序。通过研究基因序列的多样性，我们可以鉴定原始样本中存在的微孢子虫寄生虫。当我们检测到我们感兴趣的病原体(E.bieneusi和E.liver Openaei)或这些病原体的近亲时，我们将标记扩增的DNA序列并将其用作探针来确定中间宿主的身份。拟议的工作将在以下人员之间进行协作：Bryony Williams(埃克塞特大学)将提供基因组学和分子工作方面的设备、培训和专门知识；案例合作伙伴Grant Stentiford(CEFAS)将提供样本采集、野外工作以及中间宿主的鉴定方面的培训；Kallaya DangTip和Ornchuma Itthiphaisarn(泰国Mahidol大学对虾分子生物学与生物技术卓越中心)将提供虾和池塘样品。

Microsporidia are a group of over 1000 described parasitic microbes with species infecting all major animal lineages in all environments. One particularly important family of microsporidia are the Enterocytozoonidae. This is an intriguing group with members that infect hosts from both aquatic and terrestrial habitats. It includes two high profile members: Enterocytozoon bieneusi, which is one of the most common causes of AIDS-associated diarrhoea and the tiger shrimp pathogen Enterocytozoon hepatopenaei. The latter is associated with severely retarded shrimp growth, which results in considerable economic losses for millions of people in the aquaculture industry. Additionally, E. hepatopenaei has recently been shown to have jumped host causing severe disease in the edible Whiteleg Shrimp. The Enterocytozoonidae, and particularly E. hepatopenaei, given its emerging economic importance, need further study and this studentship aims to use environmental DNA to address the following two questions in Enterocytozoonidae biology:The first aim of the studentship is to answer the question of how E. hepatopenaei has spread across shrimp farms in Asia. Though initially reported from Thailand, E. hepatopenaei has also been found in China, Indonesia, Malaysia, Vietnam and India. This transmission may be mediated by movement of infected shrimp from farm to farm, or the infection may be acquired from intermediate hosts and/or contaminated feed. This project proposes to use molecular data to determine how transmission has occurred and therefore inform aquaculture policies to prevent further spread. Recent collaborative work between the proposed project partners has generated genome sequence data for E. hepatopenaei which is currently being used to design better diagnostic PCR primers to understand the prevalence of the pathogen. This project proposes to expand this work by sequencing genomes of E. hepatopenaei collected from multiple geographic locations in Thailand, from China and from both Whiteleg and Tiger shrimp hosts. The generated molecular data will be used to reconstruct evolutionary relationships between the strains and infer movement between geographic localities and hosts. The second aim addresses the question of how many undiscovered Enterocytozoonidae parasites are present in the environment. Humans and shrimps are two important hosts for the Enterocytozoonidae and both may be acquiring these infections from, as yet, unidentified intermediate hosts. This component of the project aims to identify reservoirs or carriers for important Enterocytozoonidae and further species that may have the capacity to cause human or animal disease. We will collect invertebrate samples from environments at the interface of human and aquatic animal populations, for example, domestic sewage, riverine, estuarine and coastal habitats and from shrimp ponds in Thailand. We will then extract the DNA from all these organisms along with that of their associated parasites and use state of the art gene sequencing technology to sequence the same gene for each parasite in the sample. By studying the diversity of the gene sequences we can identify the microsporidian parasites present in the original sample. When we detect our pathogens of interest (E. bieneusi and E. hepatopenaei) or close relatives of these, we will label the amplified DNA sequences and use these as probes to determine the identity of intermediate hosts.The proposed work will be supervised as a collaboration between: Bryony Williams (University of Exeter) who will provide will provide equipment, training and expertise for genomics and molecular work; CASE partner Grant Stentiford (CEFAS) who will provide training in sample collection, fieldwork and identification of intermediate hosts; Kallaya Dangtip and Ornchuma Itsathiphaisarn (Center of Excellence for Shrimp Molecular Biology and Biotechnology, Mahidol University, Thailand) who will provide shrimp and shrimp pond samples.