This document summarizes information about furunculosis, a bacterial disease that infects salmonid fish. It is caused by the bacterium Aeromonas salmonicida, which is gram-negative and non-motile. Signs of infection include hemorrhages, erosion of fins in fingerlings, and furuncles or blisters in chronically infected adults. The disease has a worldwide distribution where salmon and trout are farmed. It is transmitted through contact with infected fish or contaminated water. Control methods include disinfecting tanks and eggs and keeping water supplies free from fish.

1. Emmerich and Weibel 1894

2. CONTENTS:
 What is Furunculosis?
 What is the causal agent?
 What are the signs of infection?
 How to diagnose that disease?
 Epizootiology:
▫ Geographic and host ranges.
▫ Sources and reservoirs of infection.
▫ Modes of transmission.
▫ Incubation period.
 What are the methods of control?

3. What is Furunculosis?
• Furunculosis is a serious, septicemic*, bacterial
disease.
• Found principally in salmonid fishes.
• The common name of the disease is derived
from the presence of “blisters” or furuncules on
the surface of chronically infected* salmonids.

4. What is the causal agent?
• Bacterial species: Aeromonas salmonicida*.
•After about a 24 hour growth
period the colonies are about the
size of a pin point.
•The colonies also have a brown
pigmented color that appears after
it has been growing for 48-72
hours.

5. After Staining and Microscopic
Examination:
A gram-negative bacillus
Non-motile
Optimum growth temp: 22 and 25°C
Maximum growth temperature at 34.5°C

6. Biochemical Tests:
• It is negative for
• Indole Formation Test
• Voges-proskauer Test
• Citrate Utilization Test
• Coagulase Test
• Starch Hydrolysis
• Casein Hydrolysis
• Triglyceride Hydrolysis
• Phospholipid Hydrolysis
• Hydrogen Sulfide Production
• Citrate Utilization
• The Phenylalanine Test.
It is positive for:
Oxidase test
Lysine decarboxlase test
Methyl red test
Gelatin hydrolysis test
Catalase test.

7. What are the signs of infection?
• Fingerlings: exhibit
hemorrhages at the base of
fins and erosion of the
pectoral fins. (rare)
• In chronically infected adults,
typical “furuncules” or blisters
on the skin containing an
amorphous yellow substance
and blood may be present.

8. What are the signs of infection?
• Internal examinations
frequently reveal a bloody
fluid in the body cavity.
• Petechial hemorrhages
are commonly observed
in the body wall and
viscera.

9. How to diagnose that disease?
• Bacteriological culture.
• Biochemical testing.
• Histopathology.
• Molecular confirmation.

10. EPIZOOTIOLOGY:

11. Geographic And Host Ranges
• Epizootics have been diagnosed in numerous
cool and warmwater species
• Disease is distributed worldwide except of
Australia and south America wherever trout and
salmon and golden fish are reared.

12. SOURCES AND RESERVOIRS OF
INFECTION
• Aeromonas salmonicida is considered to be an
obligate pathogen of fish.
• It has not been found when diseased or carrier
fish are absent.
• The organism may survive for days or weeks in
water but cannot persist indefinitely in the
absence of carrier fish.

13. MODES OF TRANSMISSION
• Contact with infected or carrier fish.
• Through contaminated water.
• Contaminated clothing from one culture to
another.
• Through eggs if they are contaminated.
• It doesn’t invade the pathogen unless there are
an injury on the skin surface.
( or experimentally)

14. Incubation period:
• About 2-4 days.
• In very cold weather extend to several weeks.
• High disease infection in midsummer (July-
August )* (12C- 21C)
*New York City Weather

15. METHODS OF CONTROL
• Tanks disinfection.
• Eggs disinfection.
• Water supply kept free of fish.
• Periodically inspection

16. THERAPY
• Terramycin (oxytetracycliie) should be added.
• Sulfamerazine
• Care should be taken.

17. Source:
• http://www.glfc.org/pubs/SpecialPubs/sp83_2/pdf/chap25.pdf
• http://en.wikipedia.org/wiki/Aeromonas_salmonicida
• http://www.scotland.gov.uk/Topics/marine/Fish-
Shellfish/aquaculture/diseases/notifiableDisease/Furunculosis/Aeromonas
• Hint:
Pictures in this presentation are taken from internet websites.

18. • Thanks For listening!