Notes on the identification and collection of the diseased abalone specimens:

Abalone Viral Ganglioneuritis (AVG) is a herpes like virus (in appearance)  which attacks the ganglion nerve in the abalone.   AVG replicates in the ganglion nerve and impairs the function of the nervous system of the abalone.   The affected abalone are  unable to move about or hold on.   They find it impossible to feed or maintain being attached to their home site rocks.   The abalone then fall off and are eaten by predators or  die and rot on the bottom.  

The "brain" of the abalone is located in the head region near the mouth and the nerves run back along the foot muscle towards the tail and outwards to the sides of the foot. The effect of the virus results in the abalone losing control of its foot muscle and causes both curling of the edges of the foot and protrusion of the mouth as shown in the attached photos.

Clinically, there is anorexia, a curled footpad (paresis) and a swollen/prolapsed mouth with a protruding radula.    Histological changes are restricted to the nervous system, where there is distinctive infiltration of ganglia and nerves with moderate to high numbers of haemocytes, producing a necrotising ganglioneuritis.    A herpes-like virus was observed by electron microscopy, and transmission studies have confirmed its infectivity.    These findings were consistent with those in a report of herpes-like virus infection of cultured abalone in Taiwan in 2003.

Contacts:

1. Disease Watch Hotline
   Ph. 1800 675 888
2. Fish Reporting Hotline
   13FISH ( 13 3474 )
3. VADA Ph. 0418 292 004

Abalone infected by Ganglioneuritis Virus.

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Signs to look for:

For the diver the signs of a recent infection to look for are:

• New clean and shiny abalone shells on the seabed
• Moribund abalone, meat still intact, but with the abalone making no attempt to turn over
• On passing your hand over an abalone you would normally expect them to clamp firmly onto the rock. With infected abalone you can go back over these animals and pull them off the rocks relatively easily.
• Easy chipping of abalone off the rocks.
• Infected stock is likely to be found in patches

Identifying Ganglioneuritis in Abalone:

• For the diver and the deckhand to identify the stock as being infected, firstly examine the response of the abalone. In infected stock, very little extension of the foot is seen.
• The edges of the foot tend to curl inwards (this seems to get less as the abalone get larger
• The most obvious sign is the protrusion of the mouth.