Abalone viral ganglioneuritis

Published: 29 June 2021 Updated: 26 July 2024

Table of contents

What is AVG?

Abalone Viral Ganglioneuritis (AVG) disease is an infection of the herpes virus (AbHV), also known as haliotid herpesvirus 1 (HaHV-1), in abalone. AVG affects the nervous system and results in foot curling, mouth swelling, weakness, and ultimately death. It impacts Blacklip Abalone (Haliotis rubra rubra), Greenlip Abalone (H. laevigata), Brownlip Abalone (H. conicopora), and hybrids (H. rybra X H. laevigata), HaHV can be detected despite the absence of clinical disease, allowing surveillance during outbreaks and subsequent monitoring and zoning for management purposes.

AVG has been reported in both Victoria and Tasmania, with farmed and wild abalone affected in Victoria while in Tasmania, only AbHV has been found. AVG was eradicated from Victorian farms in 2006 but resurfaced in wild abalone populations along a significant stretch of coastline, in 2011. A significant outbreak occurred in wild and farmed abalone in Victoria during December 2005/January 2006, followed by a period of no cases until May 2021 when a diver working off the coast of Cape Nelson, Portland, Victoria, observed dead Blacklip Abalone that were confirmed to be infected by AVG. Enforced control measures were implemented in affected areas where infected abalone had been identified through a surveillance program.

What is the impact of AVG on the Australian Abalone industry?

AVG led to a decline in the wild-catch fishery, reducing from 1614 tonnes in 2004/05 to a low of 827 tonnes in 2010/11, in Victoria. However, there has been a subsequent recovery, with production volume reaching 1196 tonnes in 2012/13 (Corbeil et al., 2016). Natural recruitment has been observed on reefs previously affected by AVG. Following AVG outbreaks, HaHV was successfully eradicated from farms through complete destocking and thorough decontamination of the facilities. Subsequently, these facilities were restocked with abalone without the recurrence of AVG.

What was done in the past to solve the AVG issue?

There is currently no treatment available for AVG. Diseased abalone and infectious waste serve as the primary sources of HaHV in the environment, posing the greatest risk for spreading the infection. The virus can be transmitted through water contaminated by infected abalone or their products, such as offal, shells, or mucus, as well as fishing equipment that has been in contact with infected abalone or their habitat.

To minimise the spread of AVG from infected areas, quarantine zones, including infected, restricted, control and free areas, are established along with the implementation and enforcement of movement restrictions, such as bans and limitations. Since HaHV is transmitted through the water column and other vectors, controlling its spread in natural systems is highly challenging. Therefore, disease management focuses on containment, control, zoning, and enforcement measures. Eradication of HaHV has been achieved through destocking, decontamination, and fallowing procedures in semi-closed abalone farms and closed live holding facilities.

FRDC’s role

The FRDC has supported abalone fishers and farmers to better understand the epidemiology of HaHV, develop diagnostic tests, determine the recovery of abalone stocks, develop biosecurity plans, understand immune response to HaHV, and investigate the genetic response of wild abalone populations.

References

Anon. Department of Agriculture. 2014. Disease strategy: Abalone viral ganglioneuritis (Version 1.0). In: Australian Aquatic Veterinary Emergency Plan (AQUAVETPLAN), Australian Government Department of Agriculture, Canberra, ACT. 52pp.

Corbeil, S., Williams, L. M., Cowley, J.A., Moody, N. J. G., Crane, M. 2016. Aquatic Animal Health Subprogram: Determination of susceptibility of various abalone species and populations to the various known AbHV genotypes. FRDC project 2013-001. 36 pp.