Lymphoidal Parvo-like Virus Disease of Penaeid Shrimp

Category

Category 3 (Host Not in Canada)

Common, generally accepted names of the organism or disease agent

Lymphoidal parvo-like virus disease, LPVD, Lymphoidal parvovirus-like particles.

Scientific name or taxonomic affiliation

Lymphoidal parvo-like virus or LPV consists of intranuclear particles, 18-20 nm in diameter, sometimes in paracrystalline arrays and are associated with inclusion bodies.

Geographic distribution

Observed only in Australia. However, it is likely the LPV occurs elsewhere in the Indo-Pacific or southeast Asia.

Host species

Australian penaeids: Penaeus monodon, Penaeus merguiensis, Penaeus esculentus and hybrid P. monodon X P. esculentus.

Impact on the host

Associated with moribund wild spawners of P. merguiensis but also was observed in samples from apparently healthy culture stocks of all species listed above. However, infection caused hypertrophy, multinucleate giant cell formation and cytopthology in the lymphoid (Oka) organ.

Diagnostic techniques

Histology: Occurrence of multinucleate giant cells with mild hypertrophy of the nuclei, margination and rarefication of the chromatin, more basophilic cytoplasm and an increase in the cytoplasm to nuclear ratio within the Oka organ. Concurrently, basophilic material (possibly due to cell death and nuclear distruction) accumulation near normal lymphoidal cells. Areas of lymphoidal change were usually multifocal, discrete and bounded by a few connective tissue cells and a few elongated fibrocytes thereby producing spheroids. As the infection progresses, these spheroids or lymphoidal lobes fill with cellular debris and become encapsulated by fibrocytes. Rarely, unique eosinophilic to basophilic distinctly spherical inclusion bodies were observed in cells of the lymphoid organ, hematopoietic organs and connective tissue of other organs. LPV intranuclear inclusions are somewhat similar to IHHNV intranuclear inclusions but can be distinguished from them by being distinctly spherical in morphology, whereas IHHNV inclusions are highly irregular in shape and often contain darkly basophilic chromatin processes.

Electron Micrcoscopy: Only useful on lymphoid organ tissues with a high prevalence of LPV-type intranulcear inclusions. Paracystalline arrays of viral-like particles (18 - 20 nm in diameter) occur on the edge of the large electron-dense intranucleau inclusion.

Methods of control

No known method of prevention or control.

References

Lightner, D.V. (ed.). 1996. A Handbook of Shrimp Pathology and Diagnostic Procedures for Disease of Cultured Penaeid Shrimp. World Aquaculture Society, Baton Rouge.

Owens, L., S. DeBeer and J. Smith. 1991. Lymphoidal parvovirus-like particles in Australian penaeid prawns. Diseases of Aquatic Organisms 11: 129-134.

Citation Information

Bower, S.M. (1996): Synopsis of Infectious Diseases and Parasites of Commercially Exploited Shellfish: Lymphoidal Parvo-like Virus Disease of Penaeid Shrimp.

Date last revised: Fall 1996
Comments to Susan Bower

Date modified: