Institute of Aquaculture, University of Stirling, Stirling FK9 4LA, UK.
Vet Parasitol. 2012 May 25;186(3-4):237-44. doi: 10.1016/j.vetpar.2011.11.022. Epub 2011 Nov 12.
Ichthyophthirius multifiliis Fouquet, 1876 infections on intensively reared fish stocks can increase rapidly, which if left unmanaged, can result in the heavy loss of stock. The present study explores the efficacy of long duration, low dose (1, 2 and 5 mg L(-1)) treatments of bronopol (marketed as Pyceze™, Novartis Ltd.) in reducing the number of trophonts establishing on juvenile Oncorhynchus mykiss held under small scale culture conditions. The effect of bronopol on the colonisation success of infective theronts was also investigated by adding 2 mg L(-1) bronopol to the water prior and during the infection process. The number of parasites surviving on fish treated this way was compared to groups of fish that only received treatment after infection had occurred. The effect of bronopol on exiting trophonts throughout their external development to the point of theront release was also assessed through the delivery of 1 mg L(-1), 2 mg L(-1) and 5 mg L(-1) bronopol for up to 27 days consecutively (days 9-36 post-infection). The trial showed that a nominal dose of 2 mg L(-1) bronopol administered prior to infection significantly reduced the number of theronts surviving in the water column at the time of the initial challenge by 35-40% (P<0.05). Similarly, doses of 2 and 5 mg L(-1) bronopol administered as the first wave of mature I. multifiliis trophonts exited fish (i.e. day 11 onwards) to develop externally, reduced the number of trophonts establishing on fish as the second cycle of infection by 52-83%. Continuous application of 2 and 5 mg L(-1) bronopol throughout the second and third cycles of I. multifiliis infection gave further reductions of between 90 and 98%. The number of trophonts on the fish in the control tanks and those treated with 1 mg L(-1) and the 2 mg L(-1) dose at the time of initial infection, by comparison, were observed to increase with successive cycles of infection. From these small scale tank trials, this study demonstrates that the strategic, long duration, low dose delivery of drugs like bronopol can significantly reduce the number of trophonts establishing on fish suggesting the potential of this drug at managing I. multifiliis infections.
嗜碘泡虫（Ichthyophthirius multifiliis Fouquet，1876）感染集约化养殖鱼类的数量可能会迅速增加，如果不加管理，会导致大量鱼类死亡。本研究探索了使用长持续时间、低剂量（1、2 和 5mg/L）的溴硝醇（以 PycezeTM 的名义销售，诺华公司）处理幼年虹鳟鱼，以减少在小规模养殖条件下定居的滋养体数量的效果。通过在感染过程中向水中添加 2mg/L 的溴硝醇，研究了溴硝醇对传染性游仆虫定植成功的影响。与仅在感染发生后接受治疗的鱼类相比，比较了用这种方法处理的鱼类中存活寄生虫的数量。通过连续 27 天（感染后第 9-36 天）给予 1mg/L、2mg/L 和 5mg/L 的溴硝醇，评估了溴硝醇对整个外部发育过程中现存滋养体到释放游仆虫阶段的影响。试验表明，在感染前给予 2mg/L 的名义剂量溴硝醇可使初始挑战时水中存活的游仆虫数量减少 35-40%（P<0.05）。同样，2mg/L 和 5mg/L 的溴硝醇剂量作为第一批成熟的嗜碘泡虫滋养体从鱼体中逸出进行外部发育时，可使第二轮感染中定居在鱼体上的滋养体数量减少 52-83%。在第二和第三轮感染期间持续应用 2mg/L 和 5mg/L 的溴硝醇可进一步减少 90-98%。与感染初始时用 1mg/L 和 2mg/L 剂量处理的对照组相比，在控制箱中的鱼和用 1mg/L 和 2mg/L 剂量处理的鱼上的滋养体数量随着感染的连续循环而增加。从小规模水箱试验来看，本研究表明，战略性地、长时间、低剂量地使用溴硝醇等药物可以显著减少定居在鱼体上的滋养体数量，这表明该药物在管理嗜碘泡虫感染方面具有潜力。
