Pseudomonas Septicaemia

 

Definition:

It is an acute septicemic bacterial disease, affects the most species of fishes caused by Pseudomonas species. The disease is characterized by septicemic picture and high mortality in acute case, but ascites in chronic cases.

 

Causative agent:

1.     Pseudomonas fluorescens are recognized as one of the causal agent of bacterial haemorrhagic septicemia of fish.

2.     Pseudomonas anguilliseptica is the causal agent of red spot disease especially in Japanese eel.

Pseudomonas species are non-spore-forming, gram negative rod-shaped bacteria, all are motile usually one polar flagellum but some species may have three polar flagella. Many of them produce diffusable pigments which fluoresnce under ultraviolet. Most are cytochrome oxidase positive. The optimum temperature for growth is 20 to 25úC. Most of the strains will grow to 4úC but not at 41úC. These organisms grow well on the most common laboratory media.

 

Predisposing factors:

1.     Physical stresses such as excesses of pH.

2.     Injuries or damage to skin or scales.

3.     Reduced dissolved oxygen.

4.     Presence of toxic substance in the water.

5.     Overcrowding of the fishes in farm.

6.     Malnutrition.

7.     Heavy infestation with parasites.

 

Susceptible species:

All species of fishes are susceptible to pseudomonas infection under stress conditions.

 

Mode of transmission:

The pathogen enters the host either through the oral route or through broken or abraded skin Damaged gills are also act as route of infection. Carrier fishes may play a role in spreading of the disease.

 

Clinical signs:

There usually find erythema at the base of fins in the mouth under the lower jaw and around the anus. Small peticheal haemorrhages may develop in the peritoneum. The liver may be pale and haemorrhagic. Kidney may be soft and liquefying. In chronic cases fibrinous peritonitis is seen together with ascitis. This has been described in cyprinid fishes.

 

Diagnosis:

1.     Case history.

2.     Clinical signs and P.M.

3.     Isolation and identification of the causative agent.

 

Treatment and control:

1.     The predisposing factors must be removed.

2.     Drug sensitivity test using a bacterial isolates to determine the drug, which may be value for treatment.

3.     Good management of the fish farm.

4.     External disinfection reduces spreading of the disease.