Environmental factors and the infectious disease caused by the protozoan parasite, Perkinsus marinus, in eastern oysters (Crassostrea virginica)

Temperature and salinity are two important factors limiting the distributio n and abundance of Perkinsus marinus, a protozoan parasite of Eastern oyste rs (Crassostrea virginica). Results of laboratory studies ale consistent wi th field observations and clearly demonstrate that P. marinus susceptibilit y and disease advancement are positively correlated with temperature, salin ity and in situ number of infective cells. Laboratory findings also suggest that environmental degradation may enhance the epizootic, although disease caused by P. marinus in oysters is known to be predominantly exacerbated b y elevated temperature and salinity. Oysters cellular defence mechanisms ap pear ineffective in defence against P. marinus. Also, pollutant esposure ca used no significant effects on defence-related activities measured in oyste rs.