Stilwell Justin M, Griffin Matt J, Rosser Thomas Graham, Leary John, Hagen-Frei Katharina, Mischke Charles C, Pomaranski Eric K, Soto Esteban, Camus Alvin C
Department of Pathology, College of Veterinary Medicine, University of Georgia, 501 D.W. Brooks Drive, Athens, GA 30602, USA.
Dis Aquat Organ. 2019 Feb 7;133(1):39-46. doi: 10.3354/dao03332.
Native and introduced fish can serve as reservoirs for pathogens of cultured fish species. In the current study, 351 archived western mosquitofish Gambusia affinis collected from experimental catfish production ponds in Mississippi, USA, were surveyed histologically to evaluate their potential as vectors for fish pathogens. In addition to epitheliocystis and multiple metazoan parasites, 8 fish had widespread basophilic colonies of small Gram-positive rods associated primarily with stroma supporting the skeletal muscle and bone, as well as connective tissue components of other tissues and organ systems, such as perivascular adventitia and basement membranes. These findings were consistent with spaC-type Erysipelothrix sp. infections in ornamental fish cultured in the USA. The 16S rRNA, gyrase B (gyrB), and surface protective antigen (spa) genes were amplified and sequenced from bacterial colonies excised from paraffin-embedded tissue sections using laser capture microdissection. Molecular data confirmed the identity of a spaC-type Erysipelothrix sp., which grouped phylogenetically with spaC-type Erysipelothrix sp. from diseased ornamental fish. Given the significance of commercial catfish aquaculture in the southeastern USA and the widespread distribution of mosquitofish in catfish ponds throughout the region, infectivity trials with channel catfish Ictalurus punctatus were conducted. Catfish fingerlings were exposed to a spaC-type Erysipelothrix sp. isolate by intracoelomic injection and gavage. No mortality was observed in catfish exposed by either route, and surviving fish demonstrated no significant histopathologic lesions, suggesting channel catfish have low susceptibility to the bacteria. Further research is warranted to investigate the susceptibility of other cultured fish species to this emergent fish pathogen.
本地鱼类和外来鱼类都可能成为养殖鱼类病原体的宿主。在本研究中，对从美国密西西比州实验性鲶鱼养殖池塘收集的351条存档西部食蚊鱼（Gambusia affinis）进行了组织学调查，以评估它们作为鱼类病原体载体的可能性。除了上皮囊肿和多种后生动物寄生虫外，8条鱼有广泛的嗜碱性小革兰氏阳性杆菌菌落，主要与支持骨骼肌和骨骼的基质以及其他组织和器官系统的结缔组织成分相关，如血管外膜和基底膜。这些发现与美国养殖观赏鱼中的spaC型红斑丹毒丝菌属（Erysipelothrix sp.）感染一致。使用激光捕获显微切割技术从石蜡包埋组织切片中切下的细菌菌落中扩增并测序了16S rRNA、gyrase B（gyrB）和表面保护性抗原（spa）基因。分子数据证实了一种spaC型红斑丹毒丝菌属的身份，它在系统发育上与患病观赏鱼中的spaC型红斑丹毒丝菌属归为一类。鉴于美国东南部商业鲶鱼养殖的重要性以及食蚊鱼在该地区鲶鱼池塘中的广泛分布，对斑点叉尾鮰（Ictalurus punctatus）进行了感染试验。将鲶鱼幼鱼通过体腔注射和灌胃暴露于一种spaC型红斑丹毒丝菌属分离株。通过这两种途径暴露的鲶鱼均未观察到死亡，存活的鱼也没有明显的组织病理学损伤，这表明斑点叉尾鮰对这种细菌的易感性较低。有必要进一步研究其他养殖鱼类对这种新出现的鱼类病原体的易感性。
