Amyotrophia of Abalone

Category

Category 3 (Host Not in Canada)

Common, generally accepted names of the organism or disease agent

Amyotrophia, Epizootic fatal wasting disease.

Scientific name or taxonomic affiliation

Etiological agent is unknown. However, virus-like particles were observed in the cytoplasm of cells near the nerve trunk of diseased Haliotis discus discus examined with an electron microscope (Otsu and Sasaki 1997). Virus-like particles of similar size and retrovirus-like morphology were also isolated from diseased H. discus discus in primary cultures of abalone haemocytes but the isolates from the primary culture of abalone haemocytes did not reproduce the disease (Nakatsugawa et al 1999). Glioma and tumor-like lesions have also been associated with virus-like particles in the nervous tissues of cultured juvenile Haliotis (=Nordotis) discus in Japan (Nagatsugawa et al. 1988, Harada et al. 1993).

Geographic distribution

Various culture facilities throughout western Japan.

Host species

First observed in cultured juvenile Haliotis discus discus in the early 1980s. Initially Haliotis discus hannai was thought to be resistant to the disease. However, when the major species for seed production was changed to H. discus hannai, this species was also found to be vulnerable to amyotrophia (Nakatsugawa et al. 1999).

Impact on the host

Abalone with amyotrophia develop muscle atrophy in the mantle and foot which impedes feeding and adhesion to the substrate, followed by impaired shell growth and mortality. Epizootic mass mortalities attributable to this disease have been observed in juvenile abalone during seed production and subsequent nursery stages at several facilities in Japan. Disease usually occurs among juvenile abalone reared at 18 to 20 °C. Amyotrophia could be experimentally transmitted between abalone with a filtrate (0.22 µm membrane filter) from diseased H. discus discus, (Nakatsugawa et al 1999)

Diagnostic techniques

Gross Observations: Muscle atrophy in the mantle and foot which impedes feeding and adhesion to the substrate, followed by impaired shell growth and mortality.

Histology: Moribund and dead abalone have many tumours and muscle atrophy near the nerve trunk of the pedal ganglia and their transverse commissures. The nuclei of tumour cells were contracted and the centres of some tumours were necrotic (Nakatsugawa et al 1999). No pathogens were detected during histopathological examinations.

Electron Microscopy: Virus-like particles (about 100 nm in diameter) were observed in the cytoplasm of cells near the nerve trunk of diseased H. discus discus (Otsu and Sasaki 1997).

Culture: Virus-like particles about 100 nm in diameter and retrovirus-like morphology were isolated from diseased H. discus discus in primary cultures of abalone haemocytes but these isolates did not reproduce the disease in challenged susceptible abalone (Nakatsugawa et al 1999).

Methods of control

No known methods of prevention or control. To avoid the risk of introducing this pathogen to other culture facilities or natural stocks, only animals certified to be free of infection should be considered for transplantation from areas where the disease occurs. In addition, imported animals must be held in quarantine and assayed for cryptic or subclinical infections prior to release into the new environment.

References

Bower, S.M. 2000. Infectious diseases of abalone (Haliotis spp.) and risks associated with transplantation. In: Campbell, A. (Editor), Workshop on Rebuilding Abalone Stocks in British Columbia. Canadian Special Publication of Fisheries and Aquatic Sciences 130: 111-122.

Harada, T., N. Okazaki, Y. Otoishi, Y. Hayakawa and S.S. Kubota. 1993. Tumors in Nervous tissues of abalones, Nordotis discus. Journal of Invertebrate Pathology 62: 257-261.

Nakatsugawa, T., K. Hatai and S.S. Kubota. 1988. Histopathological findings on cultured juvenile abalone, Nordotis discus, with muscular atrophy. Fish Pathology (Tokyo) 23: 203-204. (In Japanese)

Nakatsugawa, T., T. Nagai, K. Hiya, T. Nishizawa and K. Muroga. 1999. A virus isolated from juvenile Japanese black abalone Nordotis discus discus affected with amyotrophia. Diseases of Aquatic Organisms 36: 159-161.

Otsu, R. and K. Sasaki. 1997. Virus-like particles detected from juvenile abalones (Nordotis discus discus) reared with an epizootic fatal wasting disease. Journal of Invertebrate Pathology 70: 167-168.

Citation Information

Bower, S.M. (2001): Synopsis of Infectious Diseases and Parasites of Commercially Exploited Shellfish: Amyotrophia of Abalone.

Date last revised: January 2001
Comments to Susan Bower

Date modified: