Pasteurellosis in Fish

1. Presented By : Rajesh V. Chudasama
Subject
Microbial and Parasitic Diseases of Fish and Shellfish (AHM - 304)
Pasteurellosis

2. • It is a chronic to subacute systemic infectious disease of marine and
brackish water fishes caused by Photobacterium
damselae subsp. piscicida and characterized by white granulomatous
lesions in the internal organs.
• First reported from white perch in U.S.A. in 1963.
• The affected fish show prominent white granules in the kidneys and
spleen.
• Pasteurellosis is one of the most important bacterial disease among
young cultured marine fish in Japan.
Pasteurellosis

3. • Caused by Pasteurella piscicida
• Gram negative short rod
Photobacterium damselae subsp. piscicida is a Gram negative
Photobacterium damselae subsp piscicida
colonies isolated from Chaetodon semilarvatus
Causative agent :

4. • Pasteurella piscicida causes a bacteremic septicemia
that takes one of two forms.
Acute Form Chronic Form
Clinical signs :

5. Acute Form
Few clinical signs
• Small hemorrhages around the
gill covers or the base of fins in
White perch
• Abnormal skin pigmentation
• Enlarged spleen and kidney in
Sea Bass
Gills of a sea-bass suffering pasteurellosis under low magnification. Wide area of
gill epithelial tissue necrosis next to congested,inflamed tissue.

6. • Histologically there is acute necrosis of the spleen , liver,
pancrease with no inflammation.
Histological section of spleen
from gilthead seabream
showing phagocytes containing
numerous bacteria ( arrow )
• In the acute form there are few gross pathological changes. Evidence of
edema and darkening may occur in yellowtails just before death. White
perch showed only slight hemorrhages around the gill covers or bases of
the fins.

7. Chronic Form
• Striped bass shows 1-2mm miliary lesions in the kidney and spleen that
represent a chronic inflammatory response cited by bacteria.
• Multiple, white foci on spleen and kidney (imp)
The appearance of the latter lesions has led to the names tuberculosis or
pseudotuberculosis for the disease in yellow tail.
Spleen of gilthead seabream with multiple white
foci caused by P. damsela subsp. Piscicida .
• In both chronic and acute forms, Pasteurella piscicida
occurs throughout internal organs.

8. Multifocal hepatic
necrosis

9. In chronic form
• collections of necrotic lymphoid and peripheral blood cells were present in the spleen,
• focal areas of hepatocytes undergoing coagulation necrosis were apparent in the liver,
and
• there was a conspicuous lack of an inflammatory cell response.
(C). Liver shows an area of necrosis
surrounded by fibrous connective tissue and
hemorrhagic areas.
(D). Liver show severe necrosis, edema of
hepatocytes, vacuolisation and pyknotic
nucleus and damaged blood vessels.

10. • Histopathological changes were noted in naturally and
experimentally infected gilthead sea bream.
• The spleen and kidney showed circumscribed, acute necrotic
changes and infiltration, with blood cells and masses of bacteria
plugging capillaries and interstitial spaces.
• Phagocytes containing bacteria and swollen into large globules
were seen in the spleen and kidney, and it was theorized that
swollen phagocytes blocked capillary blood flow in the organs
resulting in ischemia

11. • “Pasteurellosis” is a common disease in cultured marine fish in Japan,
including
• ayu, black sea bream,
• red sea bream, red grouper,
• oval fish, yellowtail has recently caused disease in Senegalese sole
and Atlantic bluefin
• tuna In Europe and the Mediterranean, gilthead sea bream and sea
bass were diagnosed with photobacteriosis.
Susceptible species:

12. Growing sea-bass suffering from pasteurellosis.
• Congested inflamed liver and splenomegaly with plenty of
pseudotuberculi in the congested splenic parenchymacomprise the
typical necropsy findings of pasteurellosis.
• The swim bladder is usually not distended, so the majority of the dying
and dead fish sink to the bottom

13. Young yellowtails and red sea bream (Chrysophyrs
major) are more susceptible than are older fish.
Pasteurellosis of a young bream (4g) with
splenomegaly and yellowish fluid in the gut.

14. Prophylactic chemotherapy with
• sulfonamides,
• nitrofurans,
• or antibiotics have been employed successfully, but dosages have not been published
• Daily administration of antibiotics, mixed in the feed, for 10 days is usually effective to
eliminate mortalities temporarily
Treatment and control :
Sulfonamides at 200-400 mg
per kilogram of body weight per
day or chloramphenicol at 20-
40 mg per kilogram of body
weight per day, both fed for a
minimum of 6 days, are used
to control outbreaks.

15. • http://www.aun.edu.eg/developmentvet/fish%20diseases/2_8.htm
References :

16. ….Thank You….