Effect of water temperature on mortality of Pacific oysters Crassostrea gigas associated with microvariant ostreid herpesvirus 1 (OsHV-1 µVar)

Abstract

The ostreid herpesvirus 1 microvariant (OsHV-1 µVar) causes mass mortality of Pacific oysters Crassostrea gigas. Water temperature can directly influence the incidence of disease or correlate with seasonal changes in the environment and oyster physiology that modify the susceptibility of the oysters to disease. The effect of water temperature was evaluated in controlled laboratory conditions by intramuscular injection of OsHV-1 µVar after acclimation of 8 mo old spat and 17 mo old adult oysters at 4 different temperatures (14, 18, 22 and 26°C). Mortality was 84 and 77% at 26 and 22°C, respectively, compared to 23% at 18°C and nil at 14°C. There was a statistically significant interaction between the dose of OsHV-1 µVar and water temperature. At 18°C, mortality occurred exclusively at a dose of 10 6 OsHV-1 µVar genome copies per oyster whereas at the higher temperatures, oysters challenged with 10 3 copies per oyster also died. Mortality did not occur at 14°C and OsHV-1 µVar was detected in tissues of only 1% of the oysters after 14 d. When accounting for temperature and dose, spat (8 mo) were 2.7 times more likely to die than adults (17 mo). Our study confirms a direct effect of water temperature on infection and disease caused by OsHV-1 µVar. We identified a threshold water temperature of between 14 and 18°C below which productive infection does not occur and the requirement for a higher dose of OsHV-1 µVar to initiate infection at 18°C than at 22°C. These results have implications for predicting and managing disease outbreaks caused by OsHV-1 µVar.

Suspended culture evaluation of Pacific oysterCrassostrea gigasin a tropical estuary

“…In temperate zones, on the other hand, high temperatures, particularly in summer events, can adversely affect growth and survival due to stress and susceptibility to diseases (Kantzow, Hick, Becker, & Whittington, ). Similarly, in subtropical areas (north coast of the Pacific coast of Mexico), it has been observed that increasing temperature in summer inhibits growth of shell as well as soft tissue in C. gigas producing physiological stress (Castillo‐Duran, Chavez‐Villalba, Arreola‐Lizarraga, & Barraza‐Guardado, ; Chávez‐Villalba, Arreola‐Lizárraga, Burrola‐Sánchez, & Hoyos‐Chairez, ).…”

A literature review as an aid to identify strategies for mitigating ostreid herpesvirus 1 in Crassostrea gigas hatchery and nursery systems

“…De Kantzow et al . () also showed the direct effect of water temperature on infection and disease by removing the field variables using laboratory challenge with OsHV‐1 μVar and they indicated that infection did not take place below a threshold temperature of 14–18°C.…”

“…), which was supported by De Kantzow et al . () who showed in laboratory experiments that 8‐month‐old spat were 2.7 times more likely to die after challenge with OsHV‐1 μVar than 17‐month‐old adults.…”

The complex interactions of Ostreid herpesvirus 1, Vibrio bacteria, environment and host factors in mass mortality outbreaks of Crassostrea gigas

“…De Kantzow et al . () exposed spat and adult oysters to OsHV‐1 μVar at different temperatures (14, 18, 22 and 26°C) and found direct influence of water temperatures on oyster mortalities caused by OsHV‐1 μVar exposure. Indeed, no mortality was recorded at 14°C and mortalities at 18, 22 and 26°C were 23, 77 and 84%, respectively.…”