Parasitism by the protozoan Perkinsus atlanticus favours the development of opportunistic infections

• Published in: Diseases of aquatic organisms 2001-08, Vol.46 (1), p.57-66
• Main Authors: MONTES, Juan F, DURFORT, Mercè, GARCIA-VALERO, José
• Format: Article
• Language: English
• Subjects: Animal aquaculture; Animal productions; Animals; Bacterial Infections - complications; Bacterial Infections - microbiology; Bacterial Infections - veterinary; Biological and medical sciences; Bivalvia - parasitology; Bivalvia - virology; Disease Susceptibility - veterinary; Eukaryota - physiology; Fundamental and applied biological sciences. Psychology; Gills - parasitology; Invertebrate aquaculture; Marine; Mollusca; Opportunistic Infections - microbiology; Opportunistic Infections - veterinary; Perkinsus atlanticus; Protozoan Infections, Animal - complications; Protozoan Infections, Animal - microbiology; Protozoan Infections, Animal - parasitology; Spain; Tapes semidecussatus; Virus Diseases - complications; Virus Diseases - microbiology; Virus Diseases - veterinary
• ISSN: 0177-5103; 1616-1580
• DOI: 10.3354/dao046057

It has been suggested that opportunistic pathogens could contribute to the mortality of Perkinsus atlanticus-infected clams. Examination of Tapes semidecussatus clams from the northern Mediterranean coast of Spain revealed that while 86% of the clams heavily infected with P. atlanticus were co-infected by bacteria and/or viruses, neither non-infected nor lightly P. atlanticus-infected specimens had bacterial or viral infections. The bacteria, which had a Gram-negative cell wall, were always located in the apical pole of gill epithelial cells and enclosed within membranous compartments. Bacteria-containing cells were hypertrophied and showed dysplasia with loss of cilia and microvilli. The viruses shared ultrastructural, morphologic and cytopathic characteristics of a polyomavirus. Viral particles with icosahedral symmetry were found in both the cytoplasm and the nucleus of numerous cell types. Virus-infected cells showed severe alterations, including hypertrophy, reduction of the intracellular compartments and extrusion of the nuclear envelope. Moreover, gill epithelial cells showed disorganization and swelling of the apical region, which affected the ciliary structure. Our findings show that P. atlanticus parasitism favours the development of opportunistic infections which have detrimental effects in this clam population.