Whole clam culture as a quantitative diagnostic procedure of Perkinsus atlanticus (Apicomplexa, Perkinsea) in clams Ruditapes decussatus

The protozoan parasite Perkinsus atlanticus (Azevedo, 1989) causes severe l osses among cultured clams, Ruditapes decussatus. This parasite is routinel y diagnosed by means of histology or incubation of gills in fluid thioglyco llate medium. However, in order to develop models of experimental reproduct ion of the disease, a procedure for infection intensity evaluation was requ ired. Thus, a diagnostic method has been developed, based on the culture of all clam tissues in fluid thioglycollate medium, followed by sodium hydrox ide lysis, and iodine staining of the parasites on cellulose filters. This method was compared with histology. Results suggest that histology is not s ensitive enough to detect low levels of infection. The whole-clam culture t echnique allows detection of low levels or early infection of clams by P. a tlanticus. Moreover, this method provides a quantification of infection int ensity as number of parasites per gramme wet weight tissue. (C) 1999 Elsevi er Science B.V. All rights reserved.