Development of a waterborne challenge model forFlavobacterium psychrophilum

Abstract

Flavobacterium psychrophilum is the causative agent of bacterial coldwater disease and can cause significant mortality in salmonid aquaculture. To better evaluate disease prevention or treatment methods for F. psychrophilum in the laboratory, a waterborne challenge model that mimics a natural outbreak is needed. Here we report on the development of a waterborne challenge model for F. psychrophilum in which we incorporated variables that may influence challenge success: specifically, scarification prior to bacterial exposure and culture of F. psychrophilum under iron-limited culture conditions to potentially increase the probability of establishing disease. Additionally, two F. psychrophilum strains, CSF 259-93 and THC 02-90, were used in this model to test whether there were virulence differences between strains. Mortality was significantly higher in scarred fish than unscarred fish (81.5 vs. 19.4%), supporting the hypothesis that disruptions in the dermal layer enhance mortality in F. psychrophilum waterborne challenges. Although mortality differences were not significant between iron-replete and iron-limited treatments, mortality was high overall (> 30%). There was a significant difference in mortality between CSF 259-93 and THC 02-90 treatments, although both strains caused high mortality in injection challenges. In conclusion, this waterborne challenge model can be used to evaluate potential disease prevention and treatment methods.

Assessment of cross‐protection to heterologous strains of Flavobacterium psychrophilum following vaccination with a live‐attenuated coldwater disease immersion vaccine

“…Further investigation of these mucosal responses may elucidate contributions toward B.17-ILM vaccine efficacy from this arm of the immune system. Although some recent studies have employed immersion-based F. psychrophilum challenges, there still remain some refinements with ensuring appropriate challenge periods and technique to mimic natural infectivity Long, Fehringer, LaFrentz, Call, & Cain, 2014).…”

“…Further investigation of these mucosal responses may elucidate contributions toward B.17‐ILM vaccine efficacy from this arm of the immune system. Although some recent studies have employed immersion‐based F. psychrophilum challenges, there still remain some refinements with ensuring appropriate challenge periods and technique to mimic natural infectivity (Hoare, Ngo, Bartie, & Adams, ; Long, Fehringer, LaFrentz, Call, & Cain, ). This study has incorporated a standardized and reproducible IM‐injection model that may not directly stimulate mucosal immune structures without the incorporation of immersion‐based exposure, but provides a strong systemic IgM response.…”

Overcoming the challenges of phage therapy for industrial aquaculture: A review

“…Vibriosis is responsible for important economic losses in shrimp farms and farmers lack means of defense since antibiotics are losing their killing potential and vaccines cannot be applied which probably explains the importance of vibriophage research shown on Fig. 2 (Chatterjee and Haldar, 2012). The second most targeted bacterial genus is Flavobacterium, namely F. psychrophilum which infects salmonids and is not treated by vaccines either and F. columnare which infects tilapia, salmonids, eels and catfishes (Long et al, 2014;Declercq et al, 2013). The three least research-targeted species are Aeromonas spp which infects salmonids, Pseudomonas spp targeting ayu and Lactococcus spp mainly infecting trout, tilapia and yellowtail (Fernández-Álvarez et al, 2016;Nishimori et al, 2000;Austin and Austin, 2007).…”

Polyphasic characterization reveals the presence of novel fish-associated Chryseobacterium spp. in the Great Lakes of North America

“…However, experimental infections via more natural routes of exposure (e.g. immersion) with some fishpathogenic members of the family Flavobacteriaceae were, until very recently, notoriously difficult to induce (Long et al 2014), whereas IP challenges had proven to be reproducible (Madsen & Dalsgaard 1999). Nevertheless, histopathological changes were Dis Aquat Org 113: 113-125, 2015 induced in fish that were challenged with 10 4 cfu, thereby indicating that isolate T28 is capable of negatively impacting the health of an infected host without necessarily killing it.…”