Environmental factor(s) and animal vector(s) associated with atypical Aeromonas hydrophila abundance and dissemination among channel catfish ponds

Abstract

Fish‐eating birds prey and scavenge on catfish ponds with outbreaks of an emergent, atypical Aeromonas hydrophila (AAH) and may play a critical role in the pond‐to‐pond spread of AAH. The objectives of this study were to: (a) determine if great egrets that consumed AAH‐infected fish shed enough AAH in their feces to cause a disease outbreak and (b) determine the environmental factor(s) and animal vector(s) associated with epidemic AAH dissemination. Three experimental catfish ponds within an aviary facility were stocked with naïve channel catfish fingerlings. Individually housed egrets were fed catfish fingerlings injected with AAH (treatment, Ponds 1 and 3) or uninfected catfish (control, Pond 2) and then placed in their ponds. Ponds 1 and 2 had no detectable fish mortality, whereas in Pond 3, mortality occurred on Days 15–29. Beginning on Day 15, AAH was recovered from fish, pond water, chironomids, aquatic invertebrates, snails, and mud from Pond 3. Egrets can transfer viable AAH between ponds, resulting in AAH colonization of invertebrates and fish mortality. This information is critical to understand the risk factors and epidemiology associated with the spread of AAH between catfish ponds and farms to develop best management practices for ponds before and after an AAH mortality event.