Type E botulism in salmonids and conditions contributing to outbreaks

Clostrìdìum botulinum - A cause of fish mortality

“…Ο χρωματισμός των ψαριών γίνεται σκοΰρος. 6 Οι ιστολογικές τομές των εσωτερικών οργάνων δεν εμ φανίζουν καμία αλλοίωση. Οι μικροβιολογικές και παρα-σιτολογικές εξετάσεις είναι αρνητικές.…”

“…Οι μικροβιολογικές και παρα-σιτολογικές εξετάσεις είναι αρνητικές. 6 Η επιβεβαίωση της διάγνωσης μπορεί να γίνει με το συνδυασμό ενοφθαλμι-σμοΰ σε πειραματόζωα και την ευαισθησία της τοξίνης στις υψηλές θερμοκρασίες. 7 Η τελική διάγνωση προκΰπτει μετά από απομόνωση του μικροβίου και ταυτοποίηση της τοξί νης.…”

The pathology associated with visceral toxicosis of catfish

“…As botulism is reported to produce gut stasis in mammals, 8,10 it was hypothesized that this was due to constipation often associated with animal and human botulism. 3 This lesion is not seen in channel catfish with VTC. In VTC-affected channel catfish, the gastrointestinal tract gross lesions include intestinal intussusceptions and gastric eversion into the mouth.…”

“…In studies to replicate botulism in coho salmon (Oncorhynchus kisutch), live fish developed the toxicosis and died after cannibalizing dead fish, which had their intestinal tracts inoculated with BoNT/E spores (presumably leading to sporulation and toxin formation), while those fed feed laced with BoNT/E spores did not develop the toxicosis. 3 Likewise in catfish ponds, fish may become affected after consuming toxic decomposing fish from the bottom of the pond. Anoxic conditions at the bottom of the pond allow for growth of anaerobic bacteria such as C. botulinum on the dead fish.…”

“…13 Botulism caused by C. botulinum neurotoxin type E (BoNT/E) in cultured salmonids has been reported in the United States, Britain, and Denmark. 2,3,7 In Europe, the disease was originally referred to as "bankruptcy disease" because of its devastating effects. Since the recognition of VTC as a disease entity in the late 1990s, it has occurred annually with variable prevalence (Khoo, L, Gaunt P, Mauel M: 2008, 2007 Aquatic Diagnostic Laboratory Summary Report.…”