The research team has just published new observations about the behaviour of OsHV-1 in Australia. The article appeared in the July 2013 issue of the international scientific journal Diseases of Aquatic Organisms (please see link below). The team proposed an hypothesis that the virus is transmitted in nature attached to tiny particles, probably in the plankton. This theory explains much of what has been observed during natural outbreaks in Woolooware Bay NSW over several years. Intensive field research is now required to prove this idea. It is vital that the natural transmission mechanisms of OsHV-1 are better understood because this knowledge can be applied to devise ways to reduce exposure of farmed oysters to the virus, thereby helping to mitigate economic loss.
Paul-Pont I, Dhand NK and Whittington RJ (2013). Spatial distribution of mortality in Pacific oysters Crassostrea gigas: reflection on mechanisms of OsHV-1 transmission. Diseases of Aquatic Organisms Volume 105, pages 127-138.
Summary: The ostreid herpesvirus OsHV-1 has the potential to devastate Pacific oyster Crassostrea gigas culture in Australia as it has done in many other countries, highlighting the need for a better understanding of disease expression and transmission. The aim of this study was to assess the spatial distribution of OsHV-1-associated mortalities in one of only two infected areas in Australia, Woolooware Bay (Botany Bay, New South Wales). In October 2011, healthy sentinel Pacific oysters were placed in 3 different locations at 3 different tidal levels, and OsHV-1 associated mortalities were closely monitored over 7 mo. The outbreak started in November 2011, and the disease remained active until April 2012. Three major mortality events were detected. Rather than being a propagating epizootic, it appeared that most oysters were infected from a common environmental source. The distribution of OsHV-1-associated mortalities was spatially clustered, highly variable and clearly dependent on the age of oysters and their position in the water column. Non-random distribution of mortalities at macro scale (sites several km apart) and micro scale (within rearing trays), and vertical clustering patterns in the water column are discussed in regard to factors known to influence mechanism of disease transmission in aquatic environments (hydro – dynamics, physical disturbances, host density/distribution, and variations of environmental parameters). A new hypothesis proposing that OsHV-1 may be carried through water by particles, possibly plankton, is also suggested to explain the patchy distribution of mortalities in Woolooware Bay.
To access the article directly on the DAO website, click here.