Juvenile Wels Catfish under Experimental Conditions

We have limited knowledge about the course of the European catfish virus (ECV) infection in different age groups of wels catfish (Silurus glanis). The results of this study demonstrate that an ECV strain isolated from the brown bullhead (Ameiurus nebulosus) in Hungary could cause devastating losses among juvenile wels catfish. Furthermore, the age-related mortality rate following ECV infection was investigated in three virus challenge experiments at two different virus dosages. Eight-week-old (ca. 3 g), ten-week-old (ca. 8 g), and sixteen-week-old (ca. 55 g) catfish were infected with ECV at 21°C. In the youngest age group, 96% (at a 10[sup.6] TCID[sub.50] /mL dosage) and 100% (at 10[sup.5] TCID[sub.50] /mL) mortality rates were observed, while these rates were reduced to 56% and 68% in the ten-week-old groups, respectively. The mortality was significantly higher in the virus-exposed groups than in the control ones. In the sixteen-week-old group, 23% mortality was detected at a 10[sup.5] TCID[sub.50] /mL concentration of ECV. Here, a significant difference was not found between the exposed and control groups. The performed experiments show that different age groups of wels catfish may have various susceptibility to ECV. These findings draw attention to the importance of the prevention of/protection against virus infections in juvenile (up to 3-month-old) wels catfish in aquaculture.