The prevalence of abalone herpesvirus in two Haliotis species in South China during 2002-2013

Abalones (Haliotis spp.) are economically important seafoods. However, the appearance of lethal diseases since 1999, such as those caused by low-temperature viruses, have led to the near collapse of the aquaculture industry of small abalone (H. diversicolor) in southern China. The abalone herpesvirus (AbHV) is one of these suspected low-temperature viral pathogens, but the absence of epidemic data of AbHV in abalone species in China has hampered in-depth studies of AbHV and the identification of the pathogen(s) causing abalone viral disease(s). Here, we performed the first epidemiological study on AbHV in China, using quantitative PCR. The first batch of abalone individuals (n = 1082) was collected monthly from April 2012 to October 2013 at seven sites along the coast of the South China Sea. Analyses revealed the presence of AbHV in cultured abalone in China, with a detection rate of 27.73%. Most individuals were healthy and showed a viral DNA load below 10(3) copies per ng host DNA. No effect of the culture method (artificial pond culture or open sea raft culture), shell length, or host species (H. diversicolor and H. discus hannai) on the viral load was detected. In the second batch of samples (n = 500), collected between 2002 and 2012, AbHV was detected at a detection rate of 29.20%. Ultra-high viral DNA loads (10(5) to 10(7) copies/ng host DNA) were detected in the diseased abalone samples. Artificial infection results confirmed the pathogenicity of AbHV to H. diversicolor, suggesting that AbHV is probably the pathogen responsible for the abalone low-temperature viral disease. These findings will benefit the abalone aquaculture industry, as it provides data that can be used to improve the control of viral diseases, and facilitate further AbHV-related studies.