Enteromyxum leei is a myxozoan histozoic parasite that infects the intestine of several teleost fish species. In gilthead sea bream (Sparus aurata), it provokes a chronic disease, entailing anorexia, delayed growth, reduced marketability and mortality. Direct fish-to-fish transmission, relevant in aquaculture conditions, has been demonstrated for E. leei via effluent, cohabitation, and oral and anal routes. However, the minimum time of exposure for infection has not been established, nor the possible effect on the fish immune response. Two effluent trials were performed at different temperatures (high: average of 25.6°C; and low: constant at 18°C), different times of exposure to the effluent (1, 3, 5 and 7 weeks) and different population densities. The results showed that 1 week was enough to infect 100% of fish at high temperature and 58.3% at low temperature. High temperature not only increased the prevalence of infection in posterior intestine, but also induced a higher production of specific antibodies, limiting the progression of the infection along the intestine. Longer time of exposure to the parasite and higher fish densities facilitated E. leei infection. These results show that effective diagnosis, lowering animal density and removal of infected fish are key aspects to manage this disease in aquaculture facilities.

中文翻译：

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水温，接触时间和种群密度是雷氏肠杆菌鱼对鱼实验传播的关键参数。

Enteromyxum leei是一种粘虫动物的原虫，可感染几种硬骨鱼的肠道。在金头鲷（Sparus aurata）中，它诱发了一种慢性疾病，导致厌食，生长迟缓，可销售性和死亡率降低。在水产养殖条件下，直接的鱼到鱼传播已通过废水，同居以及口服和肛门途径证明与大肠埃希氏菌有关。但是，尚未确定感染的最短接触时间，也未确定对鱼类免疫反应的影响。在不同的温度（最高：平均25.6°C；最低：恒定在18°C），暴露于污水的不同时间（1、3、5和7周）和不同的人口密度下进行了两项污水试验。结果显示1周足以在高温58下感染100％的鱼。低温下为3％。高温不仅增加了后肠感染的发生率，而且还诱导了更高的特异性抗体产生，从而限制了沿肠感染的进程。更长的时间接触寄生虫和更高的鱼类密度促进了大肠杆菌的感染。这些结果表明，有效的诊断，降低动物密度和去除受感染的鱼是在水产养殖设施中管理该病的关键方面。