Dalgaard M B, Nielsen C V, Buchmann K
Department of Veterinary Microbiology, Section of Fish Diseases, Royal Veterinary and Agricultural University, 4 Stigbøjlen, 1870 Frederiksberg Centrum, Denmark.
Dis Aquat Organ. 2003 Feb 13;53(2):173-6. doi: 10.3354/dao053173.
The susceptibility of various races of salmonids towards infections with the skin parasitic monogenean Gyrodactylus salaris Malmberg, 1957, differs markedly. Norwegian and Scottish salmon strains are known as extremely susceptible to infection, whereas Baltic salmon races such as the Neva strain (Russian origin) and the Indals river (Swedish origin) salmon have been characterized as relatively resistant. However, the status of the many other Baltic strains has remained unknown. The present study reports on the susceptibility of the Baltic salmon from the Swedish river Lule. It was shown that this strain is susceptible to infection but to a lesser extent than the Scottish salmon. Further studies showed that injection of immuno-suppressants (dexamethasone) greatly increased population growth of G. salaris on Scottish salmon but not on the Baltic salmon. Mucous cell density on fins differed between strains, and a general trend to decreased cell density on infected fish 8 wk post-infection, compared to uninfected fish, was observed. The largest decrease in mucous cell density following infection was seen in the most resistant fish. After administration of immuno-suppressants, this decrease in mucous cell density was inhibited in the Scottish salmon but not in the Baltic salmon. Thus, there seems to be a relationship between the fishes' ability to discard mucous cells and the ability to resist infections with Gyrodactylus salaris. Although the Lule salmon seems more susceptible to infection compared to previous reports on the Neva salmon, the results support the notion that Baltic salmon strains are generally more resistant than East Atlantic salmon.
各种鲑科鱼类对1957年马尔姆贝格发现的皮肤寄生单殖吸虫——鲑三代虫感染的易感性存在显著差异。挪威和苏格兰的鲑鱼品系对感染极为敏感，而波罗的海鲑鱼品种，如涅瓦河品系（俄罗斯原产）和因达尔河（瑞典原产）鲑鱼，则被认为具有相对抗性。然而，许多其他波罗的海品系的情况仍不为人知。本研究报告了来自瑞典吕勒河的波罗的海鲑鱼的易感性。结果表明，该品系易受感染，但程度低于苏格兰鲑鱼。进一步研究表明，注射免疫抑制剂（地塞米松）能极大地促进鲑三代虫在苏格兰鲑鱼上的种群增长，但对波罗的海鲑鱼则无此作用。不同品系的鳍上黏液细胞密度存在差异，且观察到，与未感染的鱼相比，感染8周后的鱼黏液细胞密度普遍呈下降趋势。感染后黏液细胞密度下降最大的是抗性最强的鱼。施用免疫抑制剂后，苏格兰鲑鱼黏液细胞密度的下降受到抑制，而波罗的海鲑鱼则没有。因此，鱼类丢弃黏液细胞的能力与抵抗鲑三代虫感染的能力之间似乎存在某种关系。尽管与之前关于涅瓦河鲑鱼的报道相比，吕勒河鲑鱼似乎更容易感染，但研究结果支持了波罗的海鲑鱼品系总体上比东大西洋鲑鱼更具抗性的观点。
