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Diseases of Aquatic Organisms

    DAO prepress abstract   -  DOI:

    Susceptibility of shellfish aquaculture species in the Chesapeake Bay and Maryland Coastal Bays to Ostreid herpesvirus-1 microvariants

    M. L. Kachmar*, K. S. Reece, M. V. Agnew, H. J. Schreier, C. A. Burge

    *Corresponding author:

    ABSTRACT: The Ostreid herpesvirus 1(OsHV-1) and its microvariants cause economically devastating mass mortalities of oysters and pose a threat to the shellfish aquaculture industry globally. OsHV-1 outbreaks can cause up to 100% mortality in the Pacific oyster (Crassostrea gigas). However, OsHV-1 and its variants have a broad host range and can infect at least seven bivalve species, including bay scallops (Argopecten irradians) and eastern oysters (Crassostrea virginica). Determining the susceptibility of economically and ecologically important bivalve species to OsHV-1 is critical for improving biosecurity and disease management to protect the aquaculture industry. Surveys of eastern oysters were conducted in June-August 2021 in the Maryland portion of the Chesapeake Bay to determine the prevalence and viral load of OsHV-1 at five aquaculture farms. Using qPCR, OsHV-1 was not detected at any sites. Experiments examined the susceptibility of single stocks of eastern oysters and hard clams (Mercenaria mercenaria) to the virus and their ability to horizontally transmit it using OsHV-1 µvar SD (San Diego, California) and OsHV-1 µvar FRA (Marennes-Olreon, France). Results showed that OsHV-1 microvariants did not cause mortality or symptomatic infection in the single stocks of eastern oysters and hard clams used in these experiments using natural infection pathways. However, the eastern oyster stock, when injected with OsHV-1, did transmit the virus to naïve Pacific oysters. Further experimentation using additional stocks and lines and establishment of surveillance programs in the East and Gulf Coasts of the US is necessary to prepare for the potential spread and impact of OsHV-1 related disease.