Inter-Research > DAO > v34 > n3 > p187-192  
Diseases of Aquatic Organisms

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DAO 34:187-192 (1998)  -  doi:10.3354/dao034187

Soft shell clams Mya arenaria with disseminated neoplasia demonstrate reverse transcriptase activity

M. L. House1,*, C. H. Kim2, P. W. Reno1

1Fish Disease Laboratory, Coastal Oregon Marine Experiment Station, Hatfield Marine Science Center, Oregon State University, Newport, Oregon 97365, USA
2Department of Microbiology, Oregon State University, Corvallis, Oregon 99331-3804, USA
*Present address: Western Fisheries Research Center, United States Geological Survey, 6505 NE 65th St., Seattle, Washington 98115, USA. E-mail:

ABSTRACT: Disseminated neoplasia (DN), a proliferative cell disorder of the circulatory system of bivalves, was first reported in oysters in 1969. Since that time, the disease has been determined to be transmissible through water-borne exposure, but the etiological agent has not been unequivocally identified. In order to determine if a viral agent, possibly a retrovirus, could be the causative agent of DN, transmission experiments were performed, using both a cell-free filtrate and a sucrose gradient-purified preparation of a cell-free filtrate of DN positive materials. Additionally, a PCR-enhanced reverse transcriptase assay was used to determine if reverse transcriptase was present in tissues or hemolymph from DN positive soft shell clams Mya arenaria. DN was transmitted to healthy clams by injection with whole DN cells, but not with cell-free filtrates prepared from either tissues from DN positive clams, or DN cells. The cell-free preparations from DN-positive tissues and hemolymph having high levels of DN cells in circulation exhibited positive reactions in the PCR-enhanced reverse transcriptase assay. Cell-free preparations of hemolymph from clams having low levels of DN (<0.1% of cells abnormal), hemocytes from normal soft shell clams, and normal soft shell clam tissues did not produce a positive reaction in the PCR enhanced reverse transcriptase assay.

KEY WORDS: Soft shell clam · Mya arenaria · Disseminated neoplasia · Reverse transcriptase activity

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