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Bacterial Diseases 1 2 3 4 5 6 Enteric redmouth - ERM (Yersinia ruckeri) Furunculosis (Aeromonas salmonicida) Coldwater disease – CWD (Flavobacterium psychrophilum) Bacterial gill disease (Flavobacterium branchiophila) Bacterial kidney disease (Renibacterium salmoninarum) Strawberry disease Yersinia ruckeri • Enteric Redmouth Disease (ERM) • “Hagerman Redmouth” primarily RBT • Rucker - First reported in 1958 in Hagerman Valley. Named in 1978 Yersinia ruckeri Host Range and Vectors • • North American outbreaks – possibly due to carrier fish or contaminated eggs from Idaho • • Sources - imported baitfish, ornamentals, bird feces, etc. Clinical Signs ERM • • Chronic: • Reddening in mouth and under operculum, and internally throughout peritoneum, intestine, and fat of the body Y. ruckeri • Obligate parasite • Generally occurs 13° - 15°C • Acute, sub acute, chronic forms Yersinia ruckeri • • Non-spore forming, straight rod • Motile with flagella • No pigment, grows slowly at 8 and 35. • Carrier State • • Intestinal shedding of organism • Stress conditions, carriers transmitted Y.r. to healthy fish but unstressed fish did not • Virulence of Y.r. • Strain typing has been done widely (Hagerman – Type I) • • Treatment and control Vaccines: • First were Ross and Klontz 1965. JFRBC 22:713-719. phenol killed (in feed) • First commercial fish vaccine: licensed by USDA in 1976 (formalin-killed whole cells) • Single most effective management tool for control of mortality due to ERM. Coldwater Disease Flavobacterium psychrophilium • Bacterial cold-water disease - CWD • First observed in Leetown WV in rainbow (peduncle disease) • Next in 1948 in Washington - lesions near tail, and on dorsum Host Range and Vectors • Serious infections in salmonids worldwide - distributed widely across NA continent • Has been linked to viral pathogens such as IHNV Host Range and Vectors • Free-living examples exist • • Resident salmonids likely carriers Clinical Signs CWD • Externally: rough appearance of skin and necrosis of fins • • May see open ulcerations on skin • External or septicemic Clinical Signs CWD • Internally: • Erratic/spiral swimming • Development of deformities and/or nervous disorders Transmission • Natural reservoirs uncertain • • Mortalities increase when IHN involved • Number one concern in Hagerman Valley Diagnosis of CWD • • • • • From clinical signs and necropsy Gram negative, Rods Gliding motility Growth best on low nutrient media Treatment and control • Extra-label use of antibiotics for control – somewhat effective (but resistance a potential problem) – • • Vaccines Furunculosis • • One of the oldest known bacterial fish pathogens • Mostly associated with salmonids, but other fish can be infected • Obligate pathogen (fish to fish transmission) Clinical signs • Acute - Adult, sub-adult, darken, stop feeding, hemorrhage base fins, internal hemorrhages • • Fingerlings - dark, dying Clinical signs • Chronic, focal dermal necrosis – BOILS • Acute septicemia • • Transmission • Horizontal • Dead fish/fecal material • Mucus - asymptomatic carriers • Sediments and associated biota Presumptive Diagnosis • Morphology, Stain, non-motile • • Non spore-forming rod (1 x 2 µm) • Pigment forming non-motile Treatment and control Antibiotics: • • Resistance can be a problem Vaccines: • Bacterial/environmental Gill Disease (Flavobacterium branchiophilum) • Gill infections primarily in juvenile fish • F. branchiophilum dominant bacterial species • Found throughout North America and other countries Clinical signs BGD • Flared gills, lethargy, swim high in water column • Gill lamellae fused/clubbed (poor oxygen transport) • Debris and bacteria present • Usually associated with poor environmental conditions or parasitic infestation Diagnosis/control Diagnosis: • Usually based on clinical signs (obvious) • Test for specific bacteria Control: • Improve environmental conditions (increase DO) • Treat fish (various chemicals), 1-5% NaCl may be method of choice Bacterial Kidney Disease Renibacterium salmoninarum • Initially described in Atlantic salmon (Scotland 1930) • Hatchery and wild salmonids • Global maybe except Australia, NZ ? Clinical signs • Systemic infection slowly progressive • • Acute and chronic forms • External: exophthalmia, blood filled blisters on skin, pale gills, etc. • Internal: multifocal grey-white nodules on kidney and other organs, cloudy fluid in body Cavity, cystic cavities in skeletal muscle, etc. Diagnosis • • • • • • • • Gram Positive Fish Pathogen 0.5 X 1 µm pairs or short chains Requires L-cystein Serum or blood enhances growth Slow growing - 20 - 60 d Survives inside phagocytic cells FAT/ELISA Clinical signs/exam Control/treatment •Erythromycin (injection of adults) • Reduce loads and transmission In feed • • Expensive and not approved for food fish • No vaccines available • Avoid infection Disease of unknown etiology • Strawberry disease – Symptoms • Reddened raised inflammation on skin • Morbidity 10-15% • Market size fish affected – Cause • Bacterial (?) • Allergic reaction (?) – Treatment • Antibiotics (withdrawal period)