college of fisheries, Agartala

1. Bacterial Cold Water Disease
in Fish
PRESENTEDBY-
Ritesh chandravanshi
M.F.Sc. Iyr. I sem.
AQC02/17

2. Introduction
The disease typically occurs at temperatures below 13⁰C,
and is most serious and prevalent below 10⁰C.
This disease is not zoonotic.
Transmission is mainly horizontal, but vertical
transmission can also occur.
It is caused by Flavobacterium psychrophilum.
F. psychrophilum is a filamentous, gram negative, and rod
shaped bacterial pathogen.

3. Histroy
The first description of BCWD in fingerling of
rainbow trout, attributed to Davis (1947).
BCWD was described in coho salmon by Borg
(1960), who isolated and named the organism
Cytophaga psychrophila.
It was subsequently reclassified, as
Flavobacterium psychrophilum, by Bernardet et
al. (1996).

4. Synonyms of BCWD
 Rainbow Trout Fry Syndrome (RTFS)
 Peduncle disease
 Cytophaga psychrophila
 Flexibacter psychrophilus
 Low temperature disease
 Bacterial fry anemia
 Tail-rot
 Systemic myxobacteriosis

5. Geographical range and species
susceptibility
 North America, United States, Western Canada, Japan, Europe,
United Kingdom, Australia.
 Salmon and Trout are the most frequently affected.
 Susceptible fish include: Brook trout, rainbow trout, brown trout,
lake trout, coho salmon, chum salmon, Atlantic salmon.
 Non- salmonid species such as Eels, Carp, Tench and Crucian carp.

6. Clinical signs
 Clinical sign of BCWD vary with size and age of fishes.
 The caudal peduncle appears whitish and the skin becomes necrotic.
 Fin and operculum hemorrhages.
 Exophthalmia, gill hemorrhages and anemia.
 Internally, Petechial hemorrhages may be present on the liver,
kidney, adipose tissue, heart, swim bladder.
 In RTFS infected sac fry, the yolk membrane become eroded.

7. Infected fishes

8. Diagnosis
 For clinical isolation and confirmed identification, the same tissues
should be streaked for single colony isolation on Cytophaga or
Tryptose Yeast Extract Agar supplemented with 5% fetal calf serum
and incubated for 7 to 10 days at 15 to 20 ⁰C.
 Typical colonies are small (0.5 to 2.0 mm dia.), mucoid, smooth,
round, convex, and entire and are easily recognized by their distinct
yellow to orange color.
 Identity of the isolate should be confirmed by plate agglutination
method.

9. Prevention, Treatment and Control
There are currently no licensed vaccines available for
the prevention of F. psychrophilum.
The most common treatments for BCWD is a
combination of one-hour flush treatments using
copper sulfate, Chloramine-T or quaternary
ammonium disinfectant such a Hyamine .
While feeding a diet medicated with Terramycin™ @
150 mg/kg of feed for 12-15 days.

10. Regulatory Status
BCWD is not generally considered to be a
disease of concern by regulatory authorities,
It is not listed by the O.I.E. Currently,
There are no accepted or validated protocols for
surveillance, inspection or certification of fish.

11. References
Roberts,R.J.(1981).The Bacteriology of Teleosts. Fish Pathology
8:302-304.
Plumb, J.A. and Hanson, L.A. Health Maintenance and Principal
Microbial Diseases of Cultured Fishes 3:375-380
Cipriano, R.C. et at. (1996). Epizootiological study of bacterial cold-
water disease in pacific salmon and further characterization of the
etiologic agent, Flexibacter psychrophila. Journal of Aquatic Animal
Health 8:28-36.