Causative agent: Ranavirus — epizootic haematopoietic necrosis virus (EHNV), an iridovirus
Epizootic Haematopoietic Necrosis (EHN) is a disease unique in the global context: it was first discovered in Australia and is caused by a ranavirus that is endemic in some Australian fish populations while being highly lethal to others. The disease holds the distinction of being the first iridovirus described in fish, and it poses an ongoing threat to Australian aquaculture, particularly rainbow trout farms and native fish populations such as Murray cod. In aquarium settings, EHN is a concern for keepers of native Australian fish — the redfin perch (English perch) acts as a reservoir host and can spread EHN to other species without always showing severe symptoms itself. Young fish and naive populations suffer the highest mortality. EHN is a notifiable disease in Australia, and any suspected outbreak must be reported to the Department of Agriculture, Fisheries and Forestry. Hobbyists keeping native Australian fish should source stock from reputable, disease-certified suppliers.
Symptoms
- •Haemorrhages on skin and fins
- •swollen abdomen
- •pale or mottled liver visible post-mortem
- •lethargy
- •loss of balance
- •mass mortality particularly in young fish
Treatment
- •No effective treatment — NOTIFIABLE disease in Australia. Euthanise affected fish. Disinfect all equipment and water. Report to DAFF.
Australian Medications
- •No treatment available — report to Australian DAFF
Commonly Affected Fish
- •Redfin perch (English perch), rainbow trout, and other native Australian fish including Murray cod
Important Notes
ENDEMIC AND NOTIFIABLE IN AUSTRALIA — first iridovirus discovered in fish. Redfin perch can carry and spread without dying. Report to DAFF.