Infectious diseases of fishes in the

MDB, including EUS

Stuart J. Rowland

and

Craig A. Boys

Outline of talk

• Introduction • Disease research • Common/important diseases • Fungal diseases • EUS

– the disease – Australia, MDB – June 2010 – conclusions and recommendations

• Observation and collections in the field • Zoonoses

Diseases do cause mortalities of native fish !!

Dead silver perch on a farm - winter sap

Dead Murray cod in Lake Mulwala September 1980 – chilodonellosis

Broad categories of diseases

• Infectious diseases – infectious agents or pathogens – protozoans – fungi – bacteria – viruses – worms

• Non-infectious diseases – environmental factors – low DO – high and low pH – high ammonia, hydrogen sulphide

Diseases in the MDB

• Few reports in native fish in the wild • EHN and GUD in exotic species

– Richard Whittington – GUD in SP

• Well know in aquaculture

– SP – MC – Rowland, Callinan and Ingram

Disease research – aquaculture • Inland Fisheries Research Station/Narrandera Fisheries

Centre – research into hatchery production; since 1978 – MC, TC, GP, SP – hatchery industry (1982/83)

• Grafton Aquaculture Centre – SP – 1990 - 2010

• Snobs Creek – MC, TC, MP – 1980 – 2010

• Native fish aquaculture industry – inland species (SP, MC, GP) – 500 tonnes annually – > 3 million fingerlings – $6.5 million

Disease publications

Type of organism Pathogen Disease Comment

Protozoan Ichthyophthirius multifiliis

Chilodonella hexasticha

Trichodina sp.

Ichthyobodo necator

Tetrahymena sp.

Coccidia sp.

Ichthyophthiriosis (white

spot, ich)

Chilodonellosis

Trichodinosis

Ichthyobodosis

Tetrahymenosis

Coccidiosis

Common; acute

Common; acute

Common; chronic

Not common; potentially acute

Rare

Rare

Myxosporidian Henneguya sp. Uncommon

Ecto-commensal

ciliate Ambiphyra sp. Rare

Monogenean Lepidotrema bidyana

Gyrodactylus sp. Gill flukes

Gill flukes Common; chronic

Rare

Copepod Ergasilus sp.

Lernaea sp. Ergasilus

Anchor worm Rare

Uncommon eastern drainage; may be

common in parts of western drainage

where carp in water supply

Fungus (mold) Saprolegnia parasitica

Aphanomyces invadans

Fungus

Winter saprolegniosis

Epizootic ulcerative

syndrome

Ubiquitous pathogen

Acute on some farms

Eastern drainage only; not common;

notifiable disease

Bacteria Flexibacter columnaris

Flexibacter, Aeromonas, Pseudomonas

Aeromonas salmonicida nova

Streptococcis iniae

Mycobacterium spp.

Aeromonas hydrophila and other spp.

Chlamydia-like bacteria

Columnaris

Tail rot, fin rot

Goldfish ulcer disease

Streptococcosis

Mycobacteriosis

Aeromonad dermatitis

Epitheliocystis

Bacterial diseases are uncommon in

silver perch culture

Virus Epizootic Haematopoietic Necrosis

Virus (EHNV)

Epizootic haematopoietic

necrosis (EHN) Not recorded naturally in silver

perch

Infectious diseases and pathogens of silver perch

Common diseases and pathogens

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Protoz

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Monoge

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Type of pathogen

Ocu

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Farms

Acute diseases – ich and chilodonellosis (GAC – 20 years)

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IchChilo

Common/important diseases Protozoan diseases

• Ichthyophthiriosis – Ich, white spot

• Freshwater fish world-wide

– MC, SP

• Ichthyophthirius multifiliis

– ciliate protozoan

• Acute disease – can cause 100% mortality within days

• Some natural immunity

Life cycle of Ichthyophthirius multifiliis

Temperature dependent: 10°C 20 days 12° - 15°C 13 – 14 days 20° - 25°C 3 – 7 days

Ichthyophthiriosis

Chilodonellosis

• Chilodonella hexasticha – ciliate protozoan – oval shape – 50 – 70 µm – cyst stage

• Common • Acute

– rapid, high mortality – SP, MC, herring

Anchor worm – Lernaea sp.

• Copepod – life cycle – temperature-dependent

• Female infestive – modified head – under skin

• Effects – lesions – infections – reduced growth – loss of condition – inhibits reproduction – morbidity – mortality

Other pathogens tapeworm round worm Ergasilus (copepod)

Henneguya (myxosporidian) Gill fluke (monogenean trematode)

Bacterial and viral diseases

• No viral diseases recorded – wild or fish farms – SP 100% mort EHN in lab

• Bacterial diseases (< 3%) – columnaris – fin rot (tail rot) – streptococcosis – mycobacteriosis – Aeromonad dermatitis – goldfish ulcer disease – epitheliocystis

columnaris

tail rot

GUD

Bacterial diseases

• External lesions – red spots; ulcers

• Internal lesions – in organs

• Exophthalmia – pop-eye

• Fluid in body cavity • Pathology and bacteriology

Aquatic fungi

• Molds – saprophytic – feed on dead matter

• Ubiquitous • Reproduction

– complex, variable – spores

Fungal hyphae and spores

Fungus on Murray cod eggs

Fungus on tail

Fungal diseases • Ubiquitous • All/most species freshwater fish

– warmwater and coldwater

• Saprolegnia parasitica

• Primary and secondary pathogens

– invade and damage skin

• Causative factors

– physical damage – parasites – stress – crowding – immune suppression

Winter saprolegniosis (silver perch, bony herring, catfish)

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Morts

Rapid drop in temp in winter: 6ºC in 10 days (day 1 – 21st May)

Total mortality silver perch

Winter saprolegniosis

Winter sap – predisposing factors

• Low water temperatures (< 15ºC) • Rapid decline (4º - 6ºC in 5 – 10 days) • Suppression of immune system • Ecto-parasites • Handling damage and stress

– partial harvests

• Poor water quality – high organic load – high ammonia – low DO – poor circulation in ponds

Epizootic ulcerative syndrome (EUS)

• Ulcerative disease – freshwater and estuarine fish

• Fungus – Aphanomyces invadans

• Invasive, rapidly spreading • Spores

– infect, germinate – grow in muscle - outwards – dermal lesions and ulcers

• Reportable disease • Australia, Asia, Africa, USA • Over 100 species

– high mortalities – varying susceptibility – carp and tilapia resistant

EUS - Australia

• First reported 1972 – Bundaberg disease – sea mullet

• Spread south 1980s – Clarence and Richmond systems – regular outbreaks – mullet, bream, whiting, flathead

• Eastern, coastal drainages – Bundaberg to Hawkesbury – Northern Territory, Western Australia

• Not MDB – prior to 2008

• Silver perch – farms in eastern drainage – severe in fingerlings

EUS - MDB

• 2008 (May) • Bony herring • Darling River (Bourke)

Outbreak of ulcerative disease – June 2010 • Barwon-Darling • 200 km • 30 locations • 5 species (14) • Prevalence

– 10%

a) b)

c) d)

e) f)

a) b)

c) d)

e) f)

bony herring (16%)

golden perch (8%)

Murray cod (5%)

spangled perch (21%)

common carp (1%)

EUS diagnosed

• Gross appearance of lesions and ulcers – EUS-distinctive – characteristic stages of progression

• Histopathology – penetrating fungal hyphae – thick-walled, non-septate – granulomas (healing, repair)

• Polymerase chain reaction (PCR) – DNA; species-specific for Aphanomyces invadans

EUS – a new disease in MDB??

• No clinical evidence – prior to 2008

• Large number of hosts – herring, GP, MC, spangled perch, carp

• Large area (200 km) • Severe ulceration in each species • Individual fish with numerous and large lesions

and ulcers

Environmental factors – flow and temp

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2008 sample 2010 sample

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2008 sample 2010 sample

Environmental factors

• 2010 outbreak – followed high flows – low temps (< 15°C) – pH (7.3 – 8.7) – DO (4.2 – 10.6)

• Other EUS outbreaks linked to: – heavy rainfall, high flows – low pH (< 6), high pH (> 9) – low DO – declining alkalinity, conductivity

• Presence of the pathogen A. invadans

Low temperatures (< 16°C) in warmwater fishes

• Immune suppression • Reduced mucus production • Enable fungi to act as primary pathogen • Winter saprolegniosis

– SP – herring – eel-tail catfish – channel catfish (USA)

Introduction of pathogens

• Spread of diseases a world-wide problem • GUD

– 1974 Japan to Australia – goldfish farms to wild

• Anchor worm (Lernaea sp.) – carp to native fish – throughout MDB

• SP, MC, GP – cultured in eastern drainage – translocation to MDB?

Conclusions and recommendations

• EUS in the MDB – an invasive disease that will spread

• Surveillance, reporting and diagnosis – determine distribution, identify hosts, susceptibility

• No translocation of fish from eastern drainages – ceased in NSW

• Restrict movement of fish – out of Barwon-Darling – aquaculture broodfish, research

• Disinfect equipment used in B-D • Implement NSW HQAP

Observations in the field moribund fish

abnormal behaviour, e.g. flashing

dead fish

lesions and ulcers

Signs – what disease is it ???

Collection of samples in the field

• Microscopic examination • Collection for histopathology, bacteriology • Moribund fish

– best for disease diagnosis – some parasites leave dead fish – contamination by bacteria

• Live/moribund – plastic bags (heavy duty) or bins – oxygen and water; sealed – keep live – chilled on ice in esky – cut out gills and/or section of skin/muscle

• Formalin (10% buffered) – excised tissues or whole fish – plastic containers – label and data

Submission of samples

Jeffrey Go Veterinary Laboratory EMAI Camden, NSW Fish pathologists Vic., Qld

Zoonoses

• Diseases transmitted to humans – immunosuppressed, elderly, children

• Spine punctures; open wounds; ingestion • Bacterial pathogens most common

– Mycobacterium, Aeromonas, Streptococcus, Vibrio

• Symptoms – skin inflammation, infection, swelling, stiffness, necrosis,

septicaemia, arthritis

• Precautions and actions – wear gloves – take care handling diseased fish – seek medical attention

THANK YOU

Native Fish Forum 2010 Canberra

15 – 16 September 2010