Abalone Viral Mortality

Category

Category 3 (Host Not in Canada)

Common, generally accepted names of the organism or disease agent

Crack-shell disease of Haliotis hannai, Haliotis diversicolor viral disease, ganglioneuritis of abalone.

Scientific name or taxonomic affiliation

Etiological agent is not fully understood but is an icosahedral virus that is a putative herpesvirus (Chang et al. 2005). Similar viral infection has been reported from mussels (Mytilus edulis) within the known distribution of diseases abalone and artificial infections achieved in the turban shell (Turbo sp.) and tegula (Tegula (=Chlorostoma) rusticum (Li et al. 2000). However, virus-like particles of about four different types have been reported from various tissues of two species of abalone (Zhengli and Handlinger 2004). The virus associated with "Abalone Viral Mortality" is not the same as the viral infections of glioma which causes Amyotrophia of Abalone in Japan.

Geographic distribution

Various culture facilities in China (including facilities in Dalian, Liaoning province along the Bohai coast line and Fujian (Dongshan Prefecture), Hainan and Guangdong provinces in the southern sea of China), Taiwan and Australia.

Host species

Haliotis discus hannai, Haliotis diversicolor (including Haliotis diversicolor aquatilis, Haliotis diversicolor supertexta and Haliotis diversicolor diversicolor), Haliotis laevigata and Haliotis rubra.

Impact on the host

Since the late winter of 1999, abalone farms in southern China have suffered heavy economic losses attributed to this virus (Nie and Wang 2004). All sizes of farmed abalone were vulnerable (Wang et al. 2004). Increased mortality rates is associated with infection and pathology was reported in the digestive tract, hepatopancreas, renal tissue, haemocytes and neural tissue. Temperatures less than 20 °C seem to be required for expression of the disease (Wang et al. 2004). The disease was experimentally transferred between abalone in which the greatest pathology associated with mortality was observed in the hepatopancreas (Song et al. 2000, Wang et al. 2004). In Taiwan, the nerve system of infected abalone was reported to be the primary target tissue (Chang et al. 2005). Vibrio alginolyticus and Vibrio parahaemolyticus may co-infect abalone which has been infected with the virus and could be co-factors for disease in H. diversicolor (Wang et al. 1999, Zhang et al. 2001a and b).

Diagnostic techniques

Gross Observations: Low activity, loss of appetite, decreased photophobia, decreased growth rate, increased secretion of mucus, contracted foot and mantle, black and hardened (stiff) foot, dead abalone present swollen hepatopancreas and digestive tract. Infection has also been associated with shell deformities including a thin shell with turned-down edge and linked respiratory holes in larval H. discus hannai (Li et al. 1998). Tanks containing diseased abalone usually filled with foam (Wang et al. 2004).

Histology: In tissue sections of the mantle, foot, gill, hepatopancreas and digestive tract stained with haematoxylin and eosin stain, the common pathological changes are: haemocyte infiltration, necrosis and disorder of the connective tissues of all infected organs and in the neurolemma of the cerebral ganglia and peripheral neural tissue; necrosis of haemocytes and epithelial cells; detachment and vacuolization of epithelial cells of the foot, mantle, hepatopancreas and gills; and hypertrophy and hyperplasia of the digestive tract epithelial cells.

Electron Microscopy: Infected cells show damage to the nuclear membrane, swelling of the mitochondria and proliferation of the endoplasmic reticulum. The virus replicates in the nucleus and maturation takes place in the cytoplasm of infected cells. The nucleocapsids (70-100 nm in diameter) occurs in the nucleus and icosahedral (hexagonal) virions (90-140 nm in diameter with a two-layer envelope (8-10 nm) and a smooth surface) are assembled in the cytoplasm.

Methods of control

No known methods of prevention or control. Infected abalone should not be transported into areas known to be free of the disease.

References

Chang, P.H., S.T. Kuo, S.H. Lai, H.S. Yang, Y.Y. Ting, C.L. Hsu and H.C. Chen. 2005. Herpes-like virus infection causing mortality of cultured abalone Haliotis diversicolor supertexta in Taiwan. Diseases of Aquatic Organisms 65: 23-27.

Li, X., B. Wang, S. Liu, M. Liu and Q. Wang. 1998. Studies on pathogeny and histopathology of "Crack Shell Disease" of Haliotis discus hanni. Journal of Fisheries of China 22: 61-66.

Li, X., B. Wang, S. Liu and J. Xu. 2000. The infection to a few kinds of shellfish inshore by a kind of virus. Journal of Dalian Fisheries University 15: 86-91.

Nie, Z. and S. Wang. 2004. The status of abalone culture in China. Journal of Shellfish Research 23: 941-945.

Song, Z., R. Ji, S. Yan, C. Chen, Y. Zhong, Y. Jiang and Z. Ni. 2000. A sphereovirus resulted in mass mortality of Haliotis diversicolor aquatilis. Journal of Fisheries of China 24: 463-466.

Wang, J., Y. Su, J. Zhang, Y. Huang, Z. Zhang, Q. Yan and D. Wang. 1999. Spring explosive epidemic disease of abalone in Dongshan District. Journal of Xiamen University (Natural Science) 38: 641-644. (In Chinese with English abstract).

Wang, J., Z. Guo, J. Feng, G. Liu, L. Xu, B. Chen and J. Pan. 2004. Virus infection in cultured abalone, Haliotis diversicolor Reeve in Guangdong Province, China. Journal of Shellfish Research 23: 1163-1168.

Zhang, Z., J. Wang, Y. Su, Q. Yan, X. Chi, H. Zhou and Y. Zhou. 2001a. Pathogeny and histopathology of the epidemic disease in Haliotis diversicolor supertexta. Journal of Xiamen University (Natural Science) 40: 949-956. (In Chinese with English abstract).

Zhang, Z., J. Wang, J. Zhang, Y. Su, Y. Huang and Q. Yan. 2001b. Bacterial diseases of Haliotis diversicolor supertexta in Dongshan, Fujian. Journal of Oceanography in Taiwan Strait 20: 193-199. (In Chinese with English abstract).

Zhengli, S. and J. Handlinger. 2004. Abalone Viral Mortality - Disease card. Developed to support the NACA/FAO/OIE regional quarterly aquatic animal disease (QAAD) reporting system in the Asia-Pacific. NACA, Bangkok, Thailand. 5 pp. (for electronic version see http://library.enaca.org/Health/DiseaseLibrary/Abalone-Disease.pdf).

Citation Information

Bower, S.M. (2007): Synopsis of Infectious Diseases and Parasites of Commercially Exploited Shellfish: Abalone viral mortality.

Date last revised: November 2007
Comments to Susan Bower

Date modified: