Soto Esteban, McGovern-Hopkins Kathleen, Klinger-Bowen Ruth, Fox Bradley K, Brock James, Antonio Nathene, Waal Zelda van der, Rushton Stephen, Mill Aileen, Tamaru Clyde S
Department of Pathobiology, Ross University, Basseterre, St. Kitts, West Indies.
J Aquat Anim Health. 2013 Jun;25(2):104-9. doi: 10.1080/08997659.2013.781554.
Francisellosis is an emergent disease in cultured and wild aquatic animals. The causative agent, Francisella noatunensis subsp. orientalis (Fno), is a gram-negative bacterium recognized as one of the most virulent pathogens of warmwater fish. The main objective of this project was to investigate the prevalence of Fno in cultured tilapia (specifically, Mozambique Tilapia Oreochromis mossambicus, Koilapia [also known as Wami Tilapia] O. hornorum, Blue Tilapia O. aureus, and Nile Tilapia O. niloticus hybrids) on the island of Oahu, Hawaii, using conventional and real-time PCR assays followed by statistical modeling to compare the different diagnostic methods and identify potential risk factors. During 2010 and 2012, 827 fish were collected from different geographical locations throughout the island of Oahu. Upon collection of fish, the water temperature in the rearing system and the length of individual fish were measured. Extraction of DNA from different tissues collected aseptically during necropsy served as a template for molecular diagnosis. High correlation between both molecular methods was observed. Moreover, the bacterium was isolated from infected tilapia on selective media and confirmed to be Fno utilizing a species-specific Taqman-based real-time PCR assay. Although a direct comparison of the prevalence of Fno between the different geographical areas was not possible, the results indicate a high prevalence of Fno DNA in cultured tilapia throughout the farm sites located on Oahu. Of the different tilapia species and hybrids currently cultured in Hawaii, Mozambique Tilapia were more susceptible to infection than Koilapia. Water temperature in the rearing systems and fish size also had a strong effect on the predicted level of infection, with fish held at lower temperatures and smaller fish being more susceptible to piscine francisellosis.
弗朗西斯菌病是养殖和野生水生动物中出现的一种疾病。病原体诺氏弗朗西斯菌东方亚种（Fno）是一种革兰氏阴性菌，被认为是温水鱼类中最具致病性的病原体之一。本项目的主要目的是利用传统PCR和实时荧光定量PCR检测，结合统计建模来比较不同诊断方法并识别潜在风险因素，调查夏威夷瓦胡岛养殖罗非鱼（具体为莫桑比克罗非鱼奥利亚罗非鱼、科伊拉罗非鱼[也称为瓦米罗非鱼]霍氏罗非鱼、蓝罗非鱼奥氏罗非鱼和尼罗罗非鱼杂交种）中Fno的流行情况。在2010年至2012年期间，从瓦胡岛不同地理位置采集了827条鱼。采集鱼时，测量了养殖系统中的水温以及每条鱼的长度。在尸检期间无菌采集不同组织并提取DNA，作为分子诊断的模板。观察到两种分子方法之间具有高度相关性。此外，在选择性培养基上从感染的罗非鱼中分离出该细菌，并利用基于Taqman的物种特异性实时荧光定量PCR检测确认其为Fno。虽然无法直接比较不同地理区域之间Fno的流行情况，但结果表明在瓦胡岛各养殖场养殖的罗非鱼中Fno DNA的流行率很高。在夏威夷目前养殖的不同罗非鱼品种和杂交种中，莫桑比克罗非鱼比科伊拉罗非鱼更容易感染。养殖系统中的水温以及鱼的大小对预测的感染水平也有很大影响，水温较低时养殖的鱼和较小的鱼更容易感染鱼类弗朗西斯菌病。
