Efficacy of phage therapy to prevent mortality during the vibriosis of brine shrimp

Phage therapy is an alternative to control bacterial pathogens in aquaculture. The extensive use is apparently feasible, however it is necessary to know its potential limitations arising from the particular characteristics of the aquatic environment in terms of the dynamics of bacterial infections, in particular because under some circumstances, the direct release of phages is the unique alternative to apply the treatment to the cultures. In the present study the efficacy of phage therapy was evaluated under gnotobiotic conditions during the induced vibriosis of Artemia franciscana. Axenic brine shrimp nauplii were infected with Vibrio parahaemolyticus and treated with phage therapy, the effect of the reduction in the phage dose and the effect of delay treatment were evaluated. The vibriosis was successfully prevented by phage therapy; a single dosage of vpms1 phage was effective to eliminate the adverse effects of V. parahaemolyticus in brine shrimp (P<0.001) and their efficacy was not affected by the reduction in the dosage, even at a multiplicity of infection of 0.45. However, its beneficial effects were compromised during the infection progress; when the application of phages was delayed, phage therapy was ineffective to control the mortality induced by V. parahaemolyticus. In conclusion, under the evaluated conditions the phage therapy was effective to prevent vibriosis in brine shrimp, however, in advanced infections their ability to control the vibriosis is limited.