1. Bacterial Diseases 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

2. Yersinia ruckeri Enteric Redmouth Disease (ERM)
“Hagerman Redmouth” primarily RBT
Rucker - First reported in 1958 in Hagerman Valley. Named in 1978 Yersinia ruckeri

3. Host Range and Vectors
North American outbreaks – possibly due to carrier fish or contaminated eggs from Idaho
Sources - imported baitfish, ornamentals, bird feces, etc.

4. Clinical Signs ERM Chronic:
Reddening in mouth and under operculum, and internally throughout peritoneum, intestine, and fat of the body

5. Y. ruckeri Obligate parasite Generally occurs 13° - 15°C
Acute, sub acute, chronic forms

6. Yersinia ruckeri Non-spore forming, straight rod Motile with flagella
No pigment, grows slowly at 8 and 35.

7. Carrier State Intestinal shedding of organism
Stress conditions, carriers transmitted Y.r. to healthy fish but unstressed fish did not

8. Virulence of Y.r.
Strain typing has been done widely (Hagerman – Type I)

9. Treatment and control Vaccines:
First were Ross and Klontz JFRBC 22: 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.

10. 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

11. Host Range and Vectors
Serious infections in salmonids worldwide - distributed widely across NA continent
Has been linked to viral pathogens such as IHNV

12. Host Range and Vectors Free-living examples exist
Resident salmonids likely carriers

13. Clinical Signs CWD
Externally: rough appearance of skin and necrosis of fins
May see open ulcerations on skin
External or septicemic

14. Clinical Signs CWD Internally: Erratic/spiral swimming
Development of deformities and/or nervous disorders

15. Transmission Natural reservoirs uncertain
Mortalities increase when IHN involved
Number one concern in Hagerman Valley

16. Diagnosis of CWD From clinical signs and necropsy Gram negative, Rods
Gliding motility
Growth best on low nutrient media

17. Treatment and control
Extra-label use of antibiotics for control – somewhat effective (but resistance a potential problem)
Vaccines

18. 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)

19. Clinical signs
Acute - Adult, sub-adult, darken, stop feeding, hemorrhage base fins, internal hemorrhages
Fingerlings - dark, dying

20. Clinical signs
Chronic, focal dermal necrosis – BOILS
Acute septicemia

21. Transmission Horizontal Dead fish/fecal material
Mucus - asymptomatic carriers
Sediments and associated biota

22. Presumptive Diagnosis
Morphology, Stain, non-motile
Non spore-forming rod (1 x 2 µm)
Pigment forming non-motile

23. Treatment and control Antibiotics: Resistance can be a problem
Vaccines:

24. Bacterial/environmental Gill Disease (Flavobacterium branchiophilum)
Gill infections primarily in juvenile fish
F. branchiophilum dominant bacterial species
Found throughout North America and other countries

25. 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

26. 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

27. Bacterial Kidney Disease Renibacterium salmoninarum
Initially described in Atlantic salmon (Scotland 1930)
Hatchery and wild salmonids
Global maybe except Australia, NZ ?

28. 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.

29. Diagnosis Gram Positive Fish Pathogen 0.5 X 1 µm pairs or short chains
Requires L-cystein
Serum or blood enhances growth
Slow growing d
Survives inside phagocytic cells
FAT/ELISA
Clinical signs/exam

30. Control/treatment Erythromycin (injection of adults)
Reduce loads and transmission
In feed
Expensive and not approved for food fish
No vaccines available
Avoid infection

31. 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)