title: Retrospective analysis of antibiotic treatments against piscirickettsiosis in farmed Atlantic salmon Salmo salar in Chile.
abstract: Piscirickettsiosis is the most prevalent salt-water infectious disease in farmed salmonids in Chile. Antimicrobials are used to treat this disease; however, there is growing concern about the poor response to therapeutants on some fish farms. The objective of this study was to assess whether factors such as type of antibiotic used, average fish weight, temperature at the beginning of the treatment, and mortality at the time of treatment administration affect the probability of treatment failure against piscirickettsiosis. Pen-level treatment and production information for the first treatment event from 2014 pens on 118 farms was used in a logistic mixed model to assess treatment failure. We defined a failed treatment as when the average mortality 3 wk after the treatment was above 0.1%. Farm and company were included in the model as random effects. We found that the antibiotic product, mortality level before the treatment, and fish weight at the start of the treatment all had a significant effect on treatment outcome. Our results suggest that antibiotic treatment success is higher if the treatment is administered when mortality associated with piscirickettsiosis is relatively low. We discuss the effect of weight on treatment success and its potential relationships with husbandry practices and drug pharmacokinetics.
authors.affiliation: Atlantic Veterinary College, University of Prince Edward Island, 550 University Avenue, Charlottetown, Prince Edward Island, Canada C1A 4P3.
authors.forename: Derek
authors.initials: D
authors.lastname: Price
authors.forename: Henrik
authors.initials: H
authors.lastname: Stryhn
authors.forename: Javier
authors.initials: J
authors.lastname: Sánchez
authors.forename: Rolando
authors.initials: R
authors.lastname: Ibarra
authors.forename: Alfredo
authors.initials: A
authors.lastname: Tello
authors.forename: Sophie
authors.initials: S
authors.lastname: St-Hilaire
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000627:therapeutic use*; D002677:Chile / Q000453:epidemiology; D005393:Fish Diseases / Q000188:drug therapy / Q000453:epidemiology / Q000382:microbiology*; D044225:Piscirickettsiaceae Infections / Q000188:drug therapy / Q000453:epidemiology / Q000662:veterinary*; D020317:Salmo salar
chemical_list: D000900:Anti-Bacterial Agents