We discovered that the water temperature prior to exposure to OsHV-1 and during the initial virus replication is an important determinant of the outcome of infection in C. gigas, either survival or death. An increase in water temperature after non-lethal viral replication at 18 °C did not lead to death. This information can be used to develop an industrial strategy to protect oysters.
de Kantzow MC, Whittington RJ and Hick PM (2019). Different in vivo growth of ostreid herpesvirus 1 at 18 °C and 22 °C alters mortality of Pacific oysters (Crassostrea gigas). Archives of Virology 164:3035–3043. https://doi.org/10.1007/s00705-019-04427-2
Summary: Seasonally recurrent outbreaks of mass mortality in Pacific oysters (Crassostrea gigas) caused by microvariant genotypes of ostreid herpesvirus 1 (OsHV-1) occur in Europe, New Zealand and Australia. The incubation period for OsHV-1 under experimental conditions is 48-72 hours and depends on water temperature, as does the mortality. An in vivo growth curve for OsHV-1 was determined by quantifying OsHV-1 DNA at 10 time points between 2 and 72 hours after exposure to OsHV-1. The peak replication rate was the same at 18 °C and 22 °C; however, there was a longer period of amplification leading to a higher peak concentration at 22 °C (2.34 x 10^7 copies/mg at 18 hours) compared to 18 °C (1.38 x 10^5 copies/mg at 12 hours). The peak viral concentration preceded mortality by 72 hours and 20 hours at 18 °C and 22 °C, respectively. Cumulative mortality to day 14 was 45.9% at 22 °C compared to 0.3% at 18 °C. The prevalence of OsHV-1 infection after 14 days at 18 °C was 33.3%. No mortality from OsHV-1 occurred when the water temperature in tanks of oysters challenged at 18 °C was increased to 22 °C for 14 days. The influence of water temperature prior to exposure to OsHV-1 and during the initial virus replication is an important determinant of the outcome of infection in C. gigas.
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