Abalone viral ganglioneuritis

Signs of disease

Important: animals with disease may show one or more of the signs below, but disease may still be present in the absence of any signs.

Disease signs at the farm level or in the wild

• high mortality up to 90 per cent
• an abundance of clean (empty) shell on substrate due to predation of moribund and dead abalone

Disease signs at the tank or pond level

• inability to adhere to substrate
• progressive mortality

Clinical signs of disease in an infected animal

• death without prior apparent clinical signs
• swollen and protruding mouth parts
• protrusion of the radula
• reduced activity of the pedal muscle
• edges of the foot curl inwards, leading to exposure of clean shiny shell
• inability to right self once placed upside down

Disease agent

Abalone viral ganglioneuritis (AVG) is caused by a herpes-like virus.

Host range

Molluscs known to be susceptible to abalone viral ganglioneuritis:

• blacklip abalone* (Haliotis rubra)
• greenlip abalone* (Haliotis laevigata)

* naturally susceptible (other species have been shown to be experimentally susceptible)

Presence in Australia

Abalone viral ganglioneuritis has been officially reported from Victoria and Tasmania.

Epidemiology

• Affects the nervous system of abalone.
• Affects all ages of abalone.
• Transmission appears to be horizontal where direct contact between infected abalone or abalone product (offal, mucus or shell) and healthy abalone is the most likely vector of transmission.
• Mortality occurs within 14 days from onset of clinical signs but can occur as rapidly as 4 days after infection.

Differential diagnosis

The differential diagnostic table and the list of similar diseases appearing at the bottom of each disease page refer only to the diseases covered by this field guide. Gross signs observed might well be representative of a wider range of diseases not included here. Therefore, these diagnostic aids should not be read as a guide to a definitive diagnosis, but rather as a tool to help identify the listed diseases that most closely account for the gross signs.

Similar diseases

Abalone viral mortality

Further images

Sample collection

Because of uncertainty in differentiating diseases using only gross signs, and because some aquatic animal disease agents might pose a risk to humans, you should not try to collect samples unless you have been trained. Instead, you should phone your state or territory hotline number and report your observations. If samples have to be collected, the agency taking the call will advise you on what you need to do. Local or district fisheries/veterinary authorities could advise you on sampling.

Emergency disease hotline

For your state or territory emergency disease hotline number, see who to contact if you suspect a disease.

Further reading

www.dpi.vic.gov.au/abalonedisease

www.vada.com.au/Virus/Virus.htm

The only procedure available for a diagnosis of abalone viral ganglioneuritis is by histology.