Pathogenicity and mechanism of bacterial, viral & fungal diseases of finfish & shellfish

Pathogenicity-

Definition- The term refers to pathogen’s characteristic ability to gain access to susceptible tissue, becomes established proliferate, avoid host defense mechanism, cause injury and disease to the host.

BACTERIAL DISEASES

1.      Piscine turberculosis

2.      Bacterial hemorrhagic septicemia (cyprinids)

3.      Red pest

4.      Red spot

5.      Vibriosis or pike pest

6.      Furunculosis

7.      Bacterial tail rot

8.      Columnaris disease

9.      Peduncle disease

10.  Bacterial gill disease

Bacterial kidney disease

11.  Ulcer disease

   Piscine tuberculosis:-

ü  Causative agent- Mycobacterium piscium, M. marinum, M. salmoniphilum .

ü  Morphology- gram +ve, non motile, acid-fast rod, length- 2 to 12 micron, optium growth temperature-25⁰ C, highest lethal temp- 37⁰C.

ü  Symptoms-

ü  internal emaciation/ hollow belly

ü  Loss of weight

ü  Loss of appetite

ü  Loss of colour & paleness

ü  Scale defect, fin rot

ü  Mandible deformity

ü  Exophthalmos/ falling out of the eyes

ü  Nodule formation in the internal organs.

ü  Prevention- aquarium hygiene

ü   Water level maintenance- 5 liter per fish.

ü  Avoid mixed tank

ü  Treatment –

ü       0.01% kanamycin in feed is effective.

Bacterial hemorrhagic septicemia-

Ø  Causative agent- Aeromonas liquefaciens

Ø  Morphology- gram –ve, asporogenous, monotrichous rod, length- 0.4 to 0.5*0.9 microns, highest lethal temperature- 50⁰C, OGT- 22⁰C.

Ø  Symptoms-

Ø  Typical dropsy

Ø  Ulceration

Ø  Prevention- hygienic fish farm operations.

Treatent- streptomycin and chloromycetin 

Red pest disease- freshwater eel
·         Causative agent- aeromonas liquefaciens
·         Symptoms-
·         Red blotches
·         White blotches in skin
·         Ulceration
·         Swimming defect
·         Prevention- low stocking density
·         Treatment- chloromycetin therapy
 

Red spot disease- (north sea salmon, cyprinids, perch)

v  Causative agent- Pseudomonas fluorescens

v  Symptoms-

v  Round, oval whitish blotches

v  Loss of scales

v  Muscular necrosis on head

v  Ulceration at the base of fin

Prevention- low stocking density