Smith P A, Contreras J R, Larenas J J, Aguillon J C, Garces L H, Perez B, Fryer J L
Faculty of Veterinary Sciences, University of Chile, Santiago, Chile.
Dev Biol Stand. 1997;90:161-6.
Piscirickettsiosis is a septicaemic disease of salmonid fish caused by the obligated intracellular rickettsia, Piscirickettsia salmonis. This disease was first reported in 1989 in salmon cultured in sea water netpens in southern Chile where it is still a major problem causing high mortality among cultured salmonids. In recent years related agents have been reported in farmed salmonids from Ireland, Canada and Norway. Mortality, however, at these locations has been reported to be low. Because of the recent description of piscirickettsiosis and its aetiological agent, knowledge about the immune response of fish against this organism is limited. At present, there is only one paper in the literature dealing with this subject. To standardise challenge methods for testing the efficacy of vaccination, lethal dose 50% and infectivity dose 50% were determined for coho salmon (Oncorhynchus kisutch) and rainbow trout (O. mykiss) using intraperitoneal (i.p.) injections of P. salmonis. Experiments using bath challenge methods failed to reproduce the disease using rainbow trout although low levels of infection in their tissues were found. In a field trial, using formalin killed bacterins injected i.p. into pre-smolt coho salmon, the fish were naturally challenged by placing them in sea water where endemic piscirickettsiosis occurred. The results showed that some of the vaccinated fish groups experienced lower cumulative mortality than the non-vaccinated control group (X < 0.05), suggesting an immunoprotective response in these animals. A trial was also conducted with formalin-killed bacterins in rainbow trout using different antigen concentrations with and without booster injections. Fish were challenged by IP injection of P. salmonis. Vaccinated fish showed less mortality than their respective infected control. Unfortunately the challenge was not strong enough because mortality in the infected control fish was low (20%). Antibody levels measured by radio-immuno-assay increased until day 40 post vaccination. The highest levels of antibody were obtained in the sera of fish vaccinated with concentrated antigen using booster injections.
鱼类立克次氏体病是一种由专性细胞内立克次氏体——鲑鱼立克次氏体引起的鲑科鱼类败血症。该病于1989年首次在智利南部海水网箱养殖的鲑鱼中被报道，至今仍是一个主要问题，导致养殖鲑科鱼类的高死亡率。近年来，在爱尔兰、加拿大和挪威养殖的鲑科鱼类中也报告了相关病原体。然而，据报道这些地区的死亡率较低。由于鱼类立克次氏体病及其病原体的描述较新，关于鱼类对该病原体免疫反应的知识有限。目前，文献中仅有一篇论文涉及该主题。为了标准化用于测试疫苗效力的攻毒方法，通过腹腔注射鲑鱼立克次氏体，测定了银大麻哈鱼（Oncorhynchus kisutch）和虹鳟（O. mykiss）的半数致死剂量和半数感染剂量。尽管在虹鳟组织中发现了低水平感染，但使用浸浴攻毒方法的实验未能使虹鳟再现该病。在一项田间试验中，将福尔马林灭活菌苗腹腔注射入银大麻哈鱼幼鲑，通过将它们放置在发生地方性鱼类立克次氏体病的海水中使其自然感染。结果表明，一些接种疫苗的鱼群累积死亡率低于未接种疫苗的对照组（P<0.05），表明这些动物有免疫保护反应。还使用不同抗原浓度的福尔马林灭活菌苗对虹鳟进行了试验，有无加强注射。通过腹腔注射鲑鱼立克次氏体对鱼进行攻毒。接种疫苗的鱼死亡率低于各自的感染对照组。不幸的是，攻毒强度不够，因为感染对照组鱼的死亡率较低（20%）。通过放射免疫测定法测量的抗体水平在接种疫苗后第40天之前升高。使用加强注射接种浓缩抗原的鱼血清中抗体水平最高。
