Reducing the impact of HaHV-1 in Australian abalone: The role of age and immune priming

Abalone (Haliotis sp.) are marine organisms of significant ecological and economic importance. However, disease outbreaks, particularly caused by Haliotid herpesvirus (HaHV-1), pose a major threat to the global aquaculture industry. HaHV-1 causes Abalone Viral Ganglioneuritis (AVG) and has led to significant economic losses due to mass mortality in farmed and wild abalone in regions such as China, Taiwan, and Australia. The current study investigated the effect of age on the susceptibility of Australian hybrid abalone to HaHV-1 and the potential of immune priming as a strategy to protect abalone from HaHV-1 infection. Using a co-housed immersion challenge model, we found that abalone less than one year of age were significantly less susceptible to HaHV-1 infection and exhibit less pronounced clinical signs of HaHV-1 infection when compared to adults. Additionally, immune priming adult abalone with poly(I:C) prior to viral challenge provided protection against HaHV-1 when compared to abalone primed with a bacterial antigen, Flagellin-A and unprimed controls. We also determined that the use of pedal swabs is a less invasive method for confirming positive HaHV-1 infections, but not for determining comparative viral loads. These findings are pivotal in developing preventative strategies against HaHV-1 in aquaculture and highlight the need for further research on immune priming and age-related susceptibility in abalone.