EVALUATION OF ABALONE VIRAL GANGLIONEURITIS RESISTANCE AMONG WILD ABALONE POPULATIONS ALONG THE VICTORIAN COAST OF AUSTRALIA

Between May 2006 and February 2010, abalone viral ganglioneuritis caused by abalone herpes virus (AbHV) spread along the coast of Victoria, Australia, and devastated wild abalone populations, causing high mortality (up to 90% in some areas). However, some abalone from the affected populations survived the epizootic and thus may be naturally resistant to the disease. To test this hypothesis, abalone (Haliotis rubra) from 5 reefs within the geographical range for AVG were collected and tested for resistance to infection and disease. Thus, mature survivors (abalone similar to 160 mm in length) and juvenile "new recruits" (abalone similar to 70 mm in length) were exposed to the virus using an experimental infectivity model to determine the presence of any potential resistance to the virus. Exposure to AbHV was performed by immersion using 3 serial viral dilutions to ensure that abalone were exposed to at least 1 viral concentration that would provide a morbidity dose of intermediate level. Results indicated that morbidity curves for the wild abalone groups (both mature and juvenile) were similar to those of the susceptible, naive, farmed hybrid (Haliotis laevigata X Haliotis rubra) abalone (positive control) groups. Histological lesions typical of abalone viral ganglioneuritis, and viral DNA, were detected in moribund, challenged abalone, confirming AbHV as the causative disease agent. Results suggest that the surviving wild abalone are not resistant to AbHV and were probably not exposed to pathogenic doses of the virus during the initial outbreak that commenced in 2006.