Mycobacteriosis or fish tuberculosis

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MYCOBACTERIOSIS OR FISH TUBERCULOSIS PHIBI PHILIP N BFT1326 AQUACLINICS

Transcript of Mycobacteriosis or fish tuberculosis

Page 1: Mycobacteriosis or fish tuberculosis

MYCOBACTERIOSIS OR FISH TUBERCULOSIS

PHIBI PHILIP NBFT1326

AQUACLINICS

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MYCOBACTERIUM SPP.• Gram – positive, aerobic.• Acid – fast bacteria & hence won’t stain well (mycolic acid).• Non-motile.• 1.5–2.0 × 0.25–0.35 μm in size. • M. marinum, M. fortuitum, and M. chelonae.• They are found worldwide in bodies of fresh water, brackish

water and salt water.• They produce pale-cream to yellow/orange colonies on solid

Source: Wikipedia

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ENVIRONMENTAL CONDITIONS FAVOURING MYCOBACTERIA

• Low levels of dissolved oxygen. • Low pH (4-6).• High organic loads.• Warm water (27°C-38C°).

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Source: Noha fish disease diagnosis book

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CLINICAL SIGNS OF MYCOBACTERIOSIS:• Slow progression of the disease - younger fish infected with

Mycobacteriosis - no external signs.• Nonhealing, shallow to deep skin ulcers.• Hyperpigmentation.• Corneal ulcers.• Pale coloration.• Emaciation.• White nodules on viscera.Source: Noga fish disease

diagnosis book

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CONT…• Internally, 1 – 4 mm white nodules may be present on

the viscera, especially hypertrophic kidney or spleen.• When the nodules develop in the organs, edema

(excess fluid accumulation) may develop, as well as peritonitis (inflammation of the body cavity).

Source: Noga fish disease diagnosis book

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EPIDEMIOLOGY Host range:

• Virtually all freshwater and marine aquarium fish are probably susceptible, especially members of the freshwater families anabantidae, characidae, and cyprinidae. Almost 150 species of fish have been affected.

• It has recently become a serious problem in laboratory research facilities that maintain medaka/Japanese killifish (Oryzias

latipes) and zebrafish (Danio rerio).

• Mycobacteriosis has also recently become a serious problem in several species of cultured food fish such as European sea bass (Dicentrarchus labrax), Tilapia sps, and striped bass (Morone

saxatilis) especially in intensive culture systems.

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TRANSMISSION

• Shedding of bacteria from infected skin ulcers, as well as the intestine, is the major source of contagion.• Ingestion is probably the major source of infection

including fish that have recently eaten dead tank mates. • The bacteria can survive for 2 years in the environment. • Transovarian transmission has been demonstrated in

some fish, such as platy but does not occur in salmonids.

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TRANSMISSION – A CASE• Another possible concern in terms of novel host – endemic pathogens

might be much more pathogenic to exotic fish that are imported into a region for culture - An exotic fish species may be inherently more susceptible to an endemic pathogen that it has not previously encountered in nature - the exotic host may act as a major reservoir for that pathogen - amplification of that pathogen’s abundance in the environment - epidemic disease in native populations.

• This has been suspected to be one possible reason for the epidemic prevalence of Mycobacteriosis in native red sea fish species after the introduction of the European sea bass for aquaculture.

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HUMAN HEALTH CONCERNS• Although transmission from infected fish to humans is

rare, it is important to be aware of the potential occurrence• Mycobacterium spp. that cause disease in fish

occasionally cause a skin infection in people that is referred to as “fish handler's disease" or "fish tank granuloma”.

Source: Google images

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HISTOPATHOLOGY

• Chronic inflammatory response with epithelioid macrophages surrounding the bacteria. • Lesions often have necrotic centres and may have

melanomacrophages or melanocytes. • Bacteria are typically located in the centre of the

inflammatory focus.

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DIAGNOSIS• Presence of large numbers of granulomas in wet mounts especially

spleen and kidney.

• Isolation on middlebrook 7H10 agar allows definitive diagnosis by biochemical identification, as well as determination of the species involved.

• Mixed infections involving up to several mycobacterium species have been observed in some cases and the relative importance of each species to the clinical signs and disease is usually not entirely clear.

Source: Noga fish disease diagnosis book

Source: Noga fish disease diagnosis book

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TREATMENT

• This disease is insidious and difficult to eradicate. Even freezing does not kill bacteria in carcasses.• In one study, erythromycin, rifampicin, or streptomycin was

effective against experimental infections. • Kanamycin is effective in reducing clinical disease (no

eradication).• Disinfection is the best method (sodium hypochlorite, lysol,

50% ethanol, sodium chlorite).

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TREATMENT

• Although there are no vaccines commercially available against fish pathogenic Mycobacteria, it is recognised that there is a cell-mediated response in fish, i.e. in Rainbow trout.• A DNA vaccine involving the AG85A gene encoding for one of

the major secreted fibronectin binding proteins of M. marinum

and cloned in a eukaryotic expression vector stimulated a protective (120 days after vaccination) humoral immune response.

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REFERENCES

• EDWARD J NOGA. 2010. FISH DISEASE, DIAGNOSE & TREATMENT (II EDITION ). WILEY-BLACKWELL. 226-227.

• RUTH FRANCIS-FLOYD & ROY YANONG. 2012. MYCOBACTERIOSIS IN FISH. UNIVERSITY OF FLORIDA, IFAS.

• BRIAN AUSTIN & DAWN A. AUSTIN. 2012. BACTERIAL FISH PATHOGENS: DISEASE OF FARMED AND WILD FISH (V EDITION). SPRINGER. 122-126.

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