Novel atypical Aeromonas salmonicida bath challenge model for juvenile ballan wrasse (Labrus bergylta, Ascanius)

Citation

Papadopoulou A, Garvey K, Hill T, Ramirez‐Paredes JG, Monaghan SJ, Baily JL, Davie A, Katsiadaki I, Verner‐Jeffreys D, Wallis T, Migaud H & Adams A (2021) Novel atypical Aeromonas salmonicida bath challenge model for juvenile ballan wrasse (Labrus bergylta, Ascanius). Journal of Fish Diseases, 44 (6), pp. 823-835. https://doi.org/10.1111/jfd.13312

Abstract
Atypical Aeromonas salmonicida (aAs) is currently one of the most routinely recovered bacterial pathogens isolated during disease outbreaks in farmed cleaner fish, ballan wrasse (Labrus bergylta, Ascanius). Vibrionaceae family bacteria have also been isolated from ballan wrasse in Scotland. This study determined the infectivity, pathogenicity and virulence of aAs and Vibrionaceae isolates in juvenile farmed ballan wrasse (n = 50; approx. 2 g) using a bath challenge, and fish were monitored for a period of 16 days. Atypical As caused significant mortalities in contrast to Vibrionaceae isolates. Notably, differential virulence was observed between two aAs vapA type V strains at similar challenge doses. Diseased fish exhibited a systemic infection where aAs was detected in all analysed tissues (liver, spleen and kidney) by PCR and qPCR. Macroscopically, moribund and survivor fish exhibited hepatomegaly and splenomegaly. In moribund and surviving fish, histopathology showed granulomatous hepatitis with eosinophilic granular cells surrounding bacterial colonies and endocarditis along with splenic histiocytosis. This is the first report of a successful aAs bath challenge model for juvenile ballan wrasse which provides an important tool for future studies on vaccine efficacy and immunocompetence.

Keywords
atypical Aeromonas salmonicida; bath challenge; eosinophilic granular cells; gross pathology; systemic disease

Journal
Journal of Fish Diseases: Volume 44, Issue 6

• Papadopoulou Et Al 2020 Bath Challenge Model Against AAs Final Complete