EVIDENCES FOR RETROVIRAL ETIOLOGY OF THE DISSEMINATED NEOPLASIA IN COCKLES (CERASTODERMA EDULE)

Epizootic outbreaks of disseminated neoplasia have been reported in association with massive mortalities of various bivalve species. In cockles, this pathological condition was described in Ireland and France. In Galicia (NW Spain), from 1997 different populations affected by this pathology have been detected. Transmission electron microscopy allowed the visualization of virus-like particles in neoplastic cells, which resemble a retrovirus-like agent. In order to confirm this hypothesis, two different approaches were employed. On one hand, we used a commercial kit for detection and quantification of retrotranscriptase (RT) activity, based on the use of bromo-deoxyuridine triphosphate (BrdUTP) and a BrdU binding antibody conjugated to alkaline phosphatase. On the other hand, we developed a product-enhanced RT assay, using RNA of hepatitis A virus as template for cDNA synthesis mediated by the RT present in the cockle samples and a further PCR amplification of this cDNA. These two assays showed respectively positive RT activity in 90.9 and 81.8% of samples from cockles displaying disseminated neoplasia as determined by light microscopy, whereas negative results were observed in control samples. These results strongly support the hypothesis of retroviral etiology for this pathological condition.