Infectious hematopoietic necrosis virus (IHNV) and Flavobacterium psychrophilum are major pathogens of farmed rainbow trout. Improved control strategies are desired but the influence of on-farm environmental factors that lead to disease outbreaks remain poorly understood. Water reuse is an important environmental factor affecting disease. Prior studies have established a replicated outdoor-tank system capable of varying the exposure to reuse water by controlling water flow from commercial trout production raceways. The goal of this research was to evaluate the effect of constant or pulsed reuse water exposure on survival, pathogen prevalence, and pathogen load. Herein, we compared two commercial lines of rainbow trout, Clear Springs Food (CSF) and Troutex (Tx) that were either vaccinated against IHNV with a DNA vaccine or sham vaccinated. Over a 27-day experimental period in constant reuse water, all fish from both lines and treatments, died while mortality in control fish in spring water was <1%. Water reuse exposure, genetic line, vaccination, and the interaction between genetic line and water exposure affected survival (P<0.05). Compared to all other water sources, fish exposed to constant reuse water had 46- to 710-fold greater risk of death (P<0.0001). Tx fish had a 2.7-fold greater risk of death compared to CSF fish in constant reuse water (P ≤ 0.001), while risk of death did not differ in spring water (P=0.98). Sham-vaccinated fish had 2.1-fold greater risk of death compared to vaccinated fish (P=0.02). Both IHNV prevalence and load were lower in vaccinated fish compared to sham-vaccinated fish, and unexpectedly, F. psychrophilum load associated with fin/gill tissues from live-sampled fish was lower in vaccinated fish compared to sham-vaccinated fish. As a result, up to forty-five percent of unvaccinated fish were naturally co-infected with F. psychrophilum and IHNV and the coinfected fish exhibited the highest IHNV loads. Under laboratory challenge conditions, co-infection with F. psychrophilum and IHNV overwhelmed IHNV vaccine-induced protection. In summary, we demonstrate that exposure to reuse water or multi-pathogen challenge can initiate complex disease dynamics that can overwhelm both vaccination and host genetic resistance.

传染性造血坏死病毒 (IHNV) 和 嗜冷黄杆菌是养殖虹鳟鱼的主要病原体。需要改进控制策略，但导致疾病爆发的农场环境因素的影响仍然知之甚少。水回用是影响疾病的重要环境因素。先前的研究已经建立了一个复制的室外水箱系统，能够通过控制来自商业鳟鱼生产水道的水流来改变再利用水的暴露。本研究的目的是评估恒定或脉冲再利用水暴露对存活率、病原体流行率和病原体负荷的影响。在此，我们比较了虹鳟鱼的两个商业品系 Clear Springs Food (CSF) 和 Troutex (Tx)，它们要么用 DNA 疫苗接种了 IHNV，要么接种了假疫苗。在持续回用水的 27 天实验期内，来自线和处理的所有鱼都死亡，而泉水中对照鱼的死亡率<1%。水再利用暴露、遗传系、疫苗接种以及遗传系和水暴露之间的相互作用影响了存活率。磷<0.05）。与所有其他水源相比，暴露在不断重复使用的水中的鱼的死亡风险要高 46 到 710 倍（磷<0.0001)。与 CSF 鱼相比，在不断回用的水中，Tx 鱼的死亡风险高 2.7 倍（≤ 0.001），而泉水的死亡风险没有差异（磷=0.98）。与接种疫苗的鱼相比，接种假疫苗的鱼的死亡风险高 2.1 倍（磷=0.02）。与假疫苗接种的鱼相比，接种疫苗的鱼的 IHNV 流行率和载量均较低，而且出乎意料的是，嗜冷菌与假疫苗接种的鱼相比，接种疫苗的鱼与活体采样鱼的鳍/鳃组织相关的负荷较低。结果，多达 45% 的未接种疫苗的鱼自然同时感染了嗜冷菌IHNV 和共感染的鱼表现出最高的 IHNV 负荷。在实验室挑战条件下，与嗜冷菌和 IHNV 压倒了 IHNV 疫苗诱导的保护。总之，我们证明暴露于再利用水或多病原体挑战可以引发复杂的疾病动态，这可以压倒疫苗接种和宿主遗传抗性。