Skin‐injured Zebrafish,Danio rerio,are more Susceptible to Vibrio anguillarum Infection

Vibrio anguillarum, which is part of normal microflora on fish, is the causative agent of vibriosis in aquaculture. It is speculated that V. anguillarum does not affect the host in most situations, but can cause a severe disease once the host is compromised. In the study reported herein, skin‐injured and intestine‐injured zebrafish, Danio rerio, were established as a model to mimic the natural infection caused by V. anguillarum when fish suffered an injury to a mucosal surface. Our results showed the lethal dose to 50% of the population (LD₅₀) of skin‐injured zebrafish was 6.8 × 10³ colony‐forming unit (CFU)/mL, which was much lower than intestine‐injured zebrafish (1.9 × 10⁶ CFU/mL) or non‐injured zebrafish (5.5 × 10⁶ CFU/mL). With the quantitative polymerase chain reaction and immunohistochemical analysis, we found that V. anguillarum proliferated rapidly in the skin and muscle after the bacteria entered into the host via the skin injury. The bacteria were subsequently transported to the immune organs and then caused a systemic infection in the fish. However, mortality of skin‐injured zebrafish significantly decreased if the fish were allowed to heal. These results indicate that minimizing injury to the mucosal surfaces of fish, especially the skin, will reduce infections caused by V. anguillarum.