OsHV-1 survey in sea water and Crassostrea gigas tissues in two areas using different culturing systems

Póster.-- 113th Annual Meeting National Shellfisheries Association, Virtual Conference, March 22 – 25, 2021The incidence of OsHV-1 is highly associated with sea water temperature being 16ºC the threshold for disease development and oyster mortality. Culturing methods also influence the disease progression as higher density of animals and direct contact favour viral transmissions. In order to minimize the impact of the disease in culturing areas, it is also important to know the specific oceanographic and environmental conditions which could facilitate disease management strategies. One stock of oysters was split in two groups and settled in two culturing sites where massive mortalities were previously detected. In one site oysters were grown in trestles and in the other, on rope rafts. Oyster tissues and sea water were collected regularly over a two-month period. 200 ml of sea water were filtered through 40, 10, 5, 1.2 and 0.22 ¿m. Oyster mortality and sea water temperature were also recorded. OsHV-1 was detected by standard PCR and quantitative PCR in mantle oyster tissues and 1.2 µm and 0.22 µm filters. One peak of abnormal mortality associated with a rapid increase in sea water temperature was observed in oysters grown in trestles. Prevalence of infection increased to 57% and quantification of viral load in sea water reached a maximum value of 4.5x10E4 viral DNA copies/µl before the mortality episode. However, no abnormal mortalities were observed in rope rafts although sea water temperature was constantly over 16ºC and prevalence of infection reached 40%.N