Papova-Like Virus Infection of Pearl Oysters


Category 3 (Host Not in Canada)

Common, generally accepted names of the organism or disease agent

Papova-like virus of golden-lipped pearl oysters.

Scientific name or taxonomic affiliation

Virus-like particles with characteristics of the Papovaviridae.

Geographic distribution

Torres Strait in northern Australia.

Host species

Pinctada maxima. Other bivalves including Crassostrea virginica and Mya arenaria were reported to be infected by papova-like viruses.

Impact on the host

Infection was observed in the labial palps of 2 out of 50 adult P. maxima during a routine histological examination of samples fished from western Torres Strait region. It is not known if infection causes disease among wild stocks. However, it is possible that this apparent virus may become more pathogenic to P. maxima under intensive culture conditions or cross-infect other hosts and produce virulent disease (Norton et al. 1993). This disease has similarities to viral gametocytic hypertrophy in C. virginica and the papova-like viral infection in the gill epithelium of M. arenaria (Farley 1976, Norton et al. 1993).

Diagnostic techniques

Histology: Lesions in the ciliated columnar epithelium of the inner surfaces of the labial palps consisted of massive hypertrophy of the epithelial cells and their nuclei. There was little or no cytoplasm visible in affected cell and no evidence of a haemocytic response. Affected nuclei were up to seven time larger in diameter than the nuclei of normal epithelial cells. The nuclear chromatin was emarginated and the central area of the affected nuclei contained an amorphous mass of eosinophilic material (with haematoxylin and eosin stain) that was Feulgen-positive. In many cases the central mass (called an inclusion) was separated from the peripheral nuclear chromatin by a clear zone.

Electron Microscopy: Non-enveloped icosahedral virus-like particles (about 60 nm in diameter) in the central mass of hypertrophied nuclei.

Methods of control

No known methods of prevention or control.


Elston, R. 1997. Special topic review: bivalve mollusc viruses. World Journal of Microbiology and Biotechnology 13: 393-403.

Farley, C.A. 1976. Proliferative disorders in bivalve mollusks. Marine Fisheries Review 38 (10): 30-33.

Farley, C.A. 1978. Viruses and viruslike lesions in marine molluscs. Marine Fisheries Review 40 (10): 18-20.

Harshbarger, J.C., S.V. Otto and S.C. Chang 1977 (1979). Proliferative disorders in Crassostrea virginica and Mya arenaria from the Chesapeake Bay and intranuclear virus-like inclusions in Mya arenaria with germinomas from a Maine oil spill site. Haliotis 8: 243-248.

Norton, J.H., M.A. Shepherd and H.C. Prior. 1993. Papovavirus-like infection of the golden-lipped pearl oyster, Pinctada maxima, from the Torres Strait, Australia. Journal of Invertebrate Pathology 62: 198-200.

Citation Information

Bower, S.M. (1997): Synopsis of Infectious Diseases and Parasites of Commercially Exploited Shellfish: Papova-Like Virus Infection of Pearl Oysters.

Date last revised: February 2010
Comments to Susan Bower

Date modified: