Abalone viral ganglioneuritis in Tasmania

Date: July 31, 2011

By Brett Herbert, Aquatic Animal Health Program, Australian Government Department of Agriculture, Fisheries and Forestry


The virus causing abalone viral ganglioneuritis (AVG) was isolated from abalone in farms and in the wild in Victoria in late 2005. The outbreak of AVG in Victoria has not spread further along the coast in the past year, and abalone farms in Victoria have been free of the disease since 2006 after decontamination of infected farms.

In 2008 and 2009, AVG was detected in Tasmania in processing plants where wild abalone are brought and held in large tanks before processing or live export. These two outbreaks were controlled and contained, and the facilities successfully decontaminated. In late December 2010, abalone at a processing facility in Tasmania displayed signs of AVG, and control measures were immediately implemented by the Tasmanian Department of Primary Industries, Parks, Water and Environment (DPIPWE). In mid-January 2011, AVG was confirmed in a second processing plant and an abalone farm. Abalone held in three other processors were found to have AVG virus present in the absence of clinical disease.

Laboratory testing incorporating both histopathology and PCR occurred at both the DPIPWE laboratories at Mount Pleasant and the Australian Animal Health Laboratory of the Commonwealth Scientific and Industrial Research Organisation. Histopathology detects disease-related changes in neural tissues, whereas PCR detects the pathogen, which, in some cases, may be present without pathology.

Quarantine restrictions were imposed on infected properties, including stopping discharge of effluent into the surrounding marine environment (except after disinfection and approval for release), and the cessation of the movement of abalone to and from the premises (except in accordance with DPIPWE biosecurity orders). A state disease control headquarters was established to oversee the response, including removal of all abalone, decontamination of the infected farm and the tracing of potential sources of the outbreak. There is a possibility that some wild
abalone from Tasmanian waters may carry the virus and that it expresses itself when abalone are stressed. This hypothesis is being investigated by the Tasmanian authorities.

All restrictions have now been lifted on all premises involved in this outbreak. Industry-wide biosecurity measures are being developed to reduce the risk AVG poses to the farmed and wild-capture sectors. There is no human health risk associated with consuming or handling abalone infected with this virus. The response to this most recent AVG outbreak followed the DPIPWE emergency animal disease response plan. A draft disease strategy management manual for the abalone industry has been prepared and is currently under review.

Pacific oyster mortality syndrome
A syndrome caused high mortalities in farmed and feral Pacific oysters in parts of the Georges River and Botany Bay in New South Wales in late 2010. In early 2011, the disease was detected in feral Pacific oysters in the Parramatta River. High mortalities of Pacific oysters have occurred overseas, but have not been reported in Australia previously. This disease has not affected Sydney rock oysters.

The New South Wales Department of Primary Industries is managing the incident locally and has placed movement restrictions on the affected areas in Botany Bay and the Georges River to manage the risk of disease spread. The Aquatic Consultative Committee on Emergency Animal Diseases has been convened to monitor developments and to assist New South Wales in its management of the situation. The states with Pacific oyster industries (New South Wales, South Australia and Tasmania) are participating in a national surveillance program to determine the distribution of the virus in Australia. The states involved, the Australian Government Department of Agriculture, Fisheries and Forestry, and the Australian Animal Health Laboratory are contributing to this program.

NOTE: We recommend the following URLs for someinteresting information:www.dpiw.tas.gov.au/inter.nsf/WebPages/SCAN-75F423  and www.vada.com.au/Virus/Virus.htm There are plenty more if you search under "ABALONE VIRAL GANGLIONEURITIS"

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