Infected animals show gross signs of mantle regression, gaping, oedema and abscesses in the mantle. Yellow-green pustules were also observed on the inner surface of the shell. The agent causing this disease has yet to be identified, however, it is highly infectious. Low salinity seems to retard the disease.
Bower et al., 1994, Synopsis of infectious diseases and parasites of commercially exploited shellfish, Annual review of fish diseases, Vol. 4, 1-199.