INFECTIOUS PANCREATIC

NECROSIS(IPN)VISHN URAJ R.SDEPT. OF AQUATIC BIOLOGY AND FISHERIESUNIVERSITY OF KERALA

INTRODUCTION• Infectious pancreatic necrosis (IPN) is a severe viral disease of

salmonid fish. • It is caused by infectious pancreatic necrosis virus.• It is a member of the Birnaviridae family. • This disease mainly affects young salmonids, such as trout or

salmon, of less than six months, although adult fish may carry the virus without showing symptoms.

• .Clinical disease is particularly important in farmed Atlantic salmon (Salmo salar L.), rainbow trout (Oncorhynchus mykiss).

• The disease Results high mortality in fry and fingerlings, and rare in larger fish

• In 1941 this disease affecting brook trout fingerlings was described in Canada.

• The most striking symptom was catarrhal enteritis. Later, in 1955, the cause of this enteritis was found to be a virus.

• In Europe it was first noted in 1965 in France and has since spread across Europe, including the British Isles.

• Isolated in Pacific NW in 1960’s, wiped out brook trout in Oregon in 1971-73.

• In Norway it was first described in trout in 1975 and in 1985 it was found in salmon.

• In Chile it was described for the first time in 1985.

History

IPNV: general notes• Single capsid shell, icosohedral symmetry, no envelope• Contains two segments of DS-RNA• Fairly stable and resistant to chemicals (acid, ether, etc.), variable

resistance to freezing.• Remains infectious for 3 months in water

• Targets pancreas and hematopoietic tissues of kidney and spleen• Size: Only 65 nM in diam., smallest of fish viruses• IPNV has been found in a wide range of fresh water and marine

fish belonging to families other than salmonidae.

Etiology • The IPN virus is a birnavirus.• The original serotype isolated from rainbow trout fingerlings is

called VR-299. • Since then, several serotypes have been identified and, in 1995, two

serogroups, A and B, were established, each containing serotypes with different geographic origins.

• The most frequently found and virulent serotype is the Sp serotype.• The lethality of the virus depends on the strain, the species and age

of the fish.• Predisposing stress-inducing factors, such as first feeding, high

stocking density, fluctuations in water temperature, salinity and handling, are believed to favour the onset of clinical disease.

• Outbreaks can occur all year round, at water temperatures as low as 4 ° C and as high as 18 °C.

Sources of the Virus• Virus is shed via faeces, sexual fluids and probably urine• Infected transport water, contaminated nets, containers and other

equipment• Infectious virus can be transported and excreted by fish-eating

birds and mammals• Horizontally by contact through the water route and by ingestion

of infected material• Vertically (via fertilized eggs) from spawning carrier broodfish• Direct contact with secretions from clinically infected fish• Asymptomatic virus carrier fish or infected embryonated ova may

introduce the virus into healthy stocks

Clinical signs• A sharp rise in mortality is often seen (depending on the virulence

of the disease).• Other clinical signs include abdominal swelling, and

Corkscrewing/spiral/whirling swimming motion• Also show anorexia, darkening of the skin, and trailing of the

faeces from the vent. Long thin whitish faecal casts,Mild to moderate exophthalmia, Gills typically pale

• On necropsy, internal damage (viral necrosis) to the pancreas and thick mucus in the intestines often is present.

• Surviving fish should recover within one to two weeks. They act as carriers

IPN: pathology (what do we see?)

diagnosis• Post Mortal Diagnosis • Internal Gross Lesions:• No food in the gastro-intestinal tract; instead filled with mucoid

whitish material• Ascetic fluid in abdominal cavity• Pinprick haemorrhages on the viscera• Pale and enlarged liver and spleen• RT-PCR techniques and in situ hybridisation have recently been

developed and proven to be valuable diagnostic tools. • IPNV is an Aquabirnavirus the presence of which can be

confirmed by isolation in tissue culture and identification by Enzyme Linked Immuno Sorbant Assay (ELISA), antibody neutralisation or Polymerase Chain Reaction (PCR).

Management• The virus is very resistant to various and adverse environmental

conditions. • Control of the microbiological water quality is therefore a critical

point in the prevention of the disease in the hatchery• Broodstock fish need to be carefully screened using the

previously mentioned assays, to detect carriers of the virus. • Disinfection of eggs is advised as a routine practice.• Prevention during the grow-out, marine phase of the production

cycle is best achieved through injection vaccination of healthy fish at the hatchery.

• IPNV is a very robust virus and can be transmitted in fresh and salt water, on equipment, and can survive in silage waste and in the gut of birds and mammals, allowing it to be transmitted in faeces.

• Movement of equipment from infected sites should be avoided, and mortalities and other wastes should be regarded as highly infectious.

Fish severely affected by IPNV:

• Atlantic salmon* (Salmo salar)• brook trout* (Salvelinus fontinalis)• brown trout* (Salmo trutta)• danio zebrafish* (Brachydanio rerio)• rainbow trout* (Oncorhynchus mykiss)• yellowtail* (Seriola lalandi)

Other species known to be susceptible…• amago salmon (Oncorhynchus rhodurus)

Arctic char (Salvelinus alpinus)Atlantic menhadden (Brevoortia tyrannus)carangids (Carangidae)chinook salmon (Oncorhynchus tshawytscha)chum salmon (Oncorhynchus keta)cichlids (Cichlidae)coho salmon (Oncorhynchus kisutch)common scallop (Pecten maximus)cutthroat trout (Salmo clarki)cyprinids (Cyprinidae)Danube salmon (Salmo hucho)drums/croakers (Sciaenidae)eels (Anguilla spp)grayling (Thymallus thymallus)

Asymptomatic carriers...• coalfish (Pollachius virens)

common carp (Cyprinus carpio)discus fish (Symphysodon discus)goldfish (Carrasius auratus)heron (Ardea cinerea)loach (Cobitidae)minnow (Phoxinus phoxinus)noble crayfish (Astacus astacus)pike (Esox lucius)river lamprey (Lampetra fluviatalis)shore crab (Carcinus maenas)Spanish barbel (Barbus graellsi)white suckers (Catostomas commersoni)

Infectious pancreatic necrosis in Atlantic salmon.

Note swollen stomach and 'pop eye'

Source: Australian Animal Health Laboratory

...what now???

However, you can always take precautions!

THANK YOU