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Haemocytic Infection Virus Disease of Oysters


Category 1 (Not Reported in Canada)

Common, generally accepted names of the organism or disease agent

Haemocytic infection virus disease (HIV).

Scientific name or taxonomic affiliation

Icosahedral DNA virus thought to be an iridovirus but affiliations with the morphologically similar viruses that cause oyster velar virus disease and gill disease in Crassostrea angulata are unknown.

Geographic distribution

France and Spain.

Host species

Crassostrea angulata and Crassostrea gigas (being cultured in France).

Impact on the host

Caused mass mortalities of C. angulata in Marenner Oleron and Brittany, France from 1970 to 1973 followed by a report of a similar type of virus infection in C. gigas in the Bay of Arcachon, France in 1977, long after the disappearance of C. angulata in that area. Most recently detected (by tissue imprints, histology and transmission electron microscopy) in 1983 and 1984 in Brittany associated with a mass mortality of C. angulata following their re-introduction for culture purposes (Mortensen et al. 2007).

Diagnostic techniques

Gross Observations: Atrophy and weakness of the adductor muscle and grayish discolouration of the viseral mass of some C. gigas (Renault and Nova 2004). However, no distinctive clinical signs were associated with the disease.

Histology: Acute inflammatory response associated with the presence of atypical haemocytes with pycnotic nuclei and round basophilic intracytoplasmic inclusion bodies (2-3  µm diameter) in the connective tissue and an increase in the number of brown cells.

Electron Microscopy: Haemocyte inclusions corresponded to virogenic stroma and the cytoplasm also contained icosahedral viral particles (380 nm diameter) with a capsid and containing an electron-opaque core. In C. gigas, virons were associated with cytoplasmic paracrystaline arrays.

Methods of control

No known methods of prevention or control. Crassostrea angulata is no longer cultured commercially and has been replaced by C. gigas which seems to be more resistant to the disease. Do not move oysters from areas with the disease (currently or historically) to areas where the disease has not been observed.


Comps, M. 1988. Epizootic diseases of oysters associated with viral infections. American Fisheries Society Special Publications 18: 23-37.

Elston, R.A. 1993. Infectious diseases of the Pacific oyster, Crassostrea gigas. Annual Review of Fish Diseases 3: 259-276.

Mortensen, S., I. Arzul, L. Miossec, C. Paillard, S. Feist, G. Stentiford, T. Renault, D. Saulnier and A. Gregory. 2007. Molluscs and crustaceans. In: Raynard, R., T. Wahli, I. Vatsos, S. Mortensen (eds.) Review of disease interactions and pathogen exchange between farmed and wild finfish and shellfish in Europe. VESO on behalf of DIPNET, Oslo. Chapter 5.3.2, pp. 325-326.

Renault, T. and B. Novoa. 2004. Viruses infecting bivalve molluscs. Aquatic Living Resources 17: 397-409.

Citation Information

Bower, S.M., McGladdery, S.E., Price, I.M. (1994): Synopsis of Infectious Diseases and Parasites of Commercially Exploited Shellfish: Haemocytic Infection Virus Disease of Oysters.

Date last revised: February 9, 2009
Comments to Susan Bower

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