Perkinsus, a protistan threat to bivalve colture in the Mediterranean Basin.

In 1978, parasites resembling Perkinsus were noted in histological preparations of Venerupis decussata probably originating from the Venice Lagoon in north-east Italy. None of 200 Crassostrea gigas from this area was infected in 1976. During the winter of 1978, Perkinsus was noted in flat oysters imported from Greece in the northern Adriatic. These findings prompted an intensive search among bivalve molluscs from 1979 to 1983. During summer 1979, considerable mortality of V. decussata from the Venice Lagoon was observed: Perkinsus was prevalent in moribund individuals. High mortalities of V. aurea were also noted in this area and samples of moribund individuals had high levels of parasites, as demonstrated by culture. Infections were also detected in Ostrea edulis, Venus verrucosa and Cerastoderma edule. The parasites are tentatively identified as P. marinus.