VPP 322: Aquatic Animal Diseases, Health Care and Management (1+1)

BACTERIAL DISEASES

• Bacterial fish diseases and infection are very common in fish. The key to successful treatment of bacterial disease is early, accurate diagnosis and treatment. If treatment is delayed it can lead to substantial losses. There are two types of pathogenic bacteria namely
  • Primary or obligate pathogens
  • Opportunistic pathogens

Primary or obligate pathogens

• These are not part of the normal aquatic flora and are capable of causing disease in healthy individuals, eg. Aeromonas salmonicida.

Opportunistic pathogens

• These are normally free-living, either in the water or on the fish, but becomes pathogenic under certain circumstances. Many of these are saprophytes, normally living on dead organic matter such as plant and animal remains or faeces, e.g., Aeromonas hydrophila and Pseudomonas spp. In general, most of the bacterial diseases that affect fishes are caused by opportunistic bacteria. Some of the common bacterial diseases are:

Bacterial disease	Causative agent	Symptoms
Columnaris	Flavobacterium columnare	Brown to yellowish brown lesion (sores) on their gills, skin, and/or fins. Characteristic lesion produced by columnaris is a pale white band (often persists as whitish plaques) encircling the body, often referred to as saddle back.
Edwardsiellosis	Edwardsiella tarda	Red cutaneous lesions located dorso-ventrally on the body Abscesses resulting in loss of pigmentation with a large amount of necrotized tissue.
Mycobacteriosis	Acid-fast bacteria of the genus Mycobacterium Mycobacterium fortuitum and Mycobacterium marinum	Anorexia, emaciation and loss of equilibrium, inflammation of the skin, exophthalmia, ascites, and open lesions, and ulceration characterize tuberculosis. Internally, grey-white granulomas develop in the liver, kidney, spleen, heart and muscles. Skin discolourations on one side of head or body
Motile aeromonad septicemia (MAS)	Aeromonas hydrophila	Manifested by several clinical signs like ulceration, exophthalmia, abdominal distention etc.
Tail rot and fin rot	Various bacteria such as Aeromonas, Pseudomonas and Mycobacterium	Fin rot and tail rot leads to the destruction of the fins especially the caudal fin. This is usually caused due to poor environmental conditions, poor nutrition and stress.
Vibriosis	Vibrio anguillarum	Red spots on the ventral and lateral areas of the fishes. Swollen dark skin lesions releasing blood exudate. In acute epizootics, the infected fish die without showing any clinical signs
Vibriosis of shell fish	Vibrio spp.	High mortalities in post-larvae, young juveniles Moribund shrimp appear hypoxic and often come to the pond surface or edge. Presence of luminescence in tanks
Necrotizing Hepatopancreatitis	Proteobacteria (alpha) group	Reduced feed intake, empty gut, anorexia, poor length: weight ratios, pallid hepatopancreas, reduced lipid droplets, melanization of tubules
Furunculosis	Aeromonas salmonicidae	Hemorrhages at the base of fins and erosion of the pectoral fins Bloody or hemorrhagic vents and petechial hemorrhages Furuncles or blisters all over the body of the fish
Enteric red mouth disease	Yersinina ruckeri	Septicemia with exophthalmus, ascites, hemorrhage and ulceration of the jaw, gills and operculum, swelling of the kidneys
Flavobacteriosis	Flavobacterium spp.	This disease is a cause of concern to primarily hobbyist and producers of ornamental fish (Mollie granuloma, Mollie madness, Mollie popeye). Infected fish are usually emaciated and pale. Multifocal white nodules are observed in the visceral organs, the retina and choroid and the brain.
Streptococcosis	Streptococcus iniae	Acute fulminating septicemia, haemorrhage of the fins, skin, and serosal surfaces, granulomas or granulomatous inflammation are evident in the liver, kidney, and brain (meningoencephalitis).
Rainbow trout fry anemia	Cytophaga psychrophila	Fish develop abdominal distention, exophthalmus, increased pigmentation, lethargy, loss of balance, pale gills, and occasional cutaneous ulcers and necrosis of tail fins. Splenomegaly and hepatomegaly are common with multifocal necrosis of the liver spleen and kidney.
Bacterial kidney disease	Renibacterium salmoninarum	Exophthalmus, skin darkening, and hemorrhage at the base of the fins. Cutaneous vesicles and ulcers may develop in mature trout "spawning rash". The large swollen kidney and spleen have numerous white nodules visible in the parenchyma Numerous granulomas (containing gram positive bacteria) are observed in the kidney and may be also present in the spleen, heart and liver
Epitheliocystis	Chlamydia sp.	Clinically infected fish may be asymptomatic or show respiratory distress or excessive mucus secretions. Multiple white cysts are observed on the gill lamella and skin.

 

Fish infected with mycobacteriosis	Fish infected with Aeromonas sp

Bacterial infection in marine fish	Reddening of mouth in catfish	Bacterial ulcer

 

 More details on microbiological procedures ....http://www.youtube.com/watch?v=Et1v8EQP10U&feature=related