Perkinsosis in molluscs: A review

Free access article

Issue		Aquat. Living Resour. Volume 17, Number 4, October-December 2004 Bivalve Diseases


Page(s)		411 - 432
DOI		10.1051/alr:2004050

Aquat. Living Resour. 17 (2004) 411-432
DOI: 10.1051/alr:2004050

Antonio Villalba¹, Kimberly S. Reece², M. Camino Ordás³, Sandra M. Casas¹ and Antonio Figueras³

¹ Centro de Investigaciones Marinas, Consellería de Pesca e Asuntos Marítimos, Xunta de Galicia, Aptdo. 13, 36620 Vilanova de Arousa, Spain
² Virginia Institute of Marine Science, The College of William and Mary, Gloucester Point VA 23062, USA
³ Instituto de Investigaciones Marinas, CSIC, Eduardo Cabello 6, 36208 Vigo, Spain

Abstract
The genus Perkinsus includes protistan parasites infecting marine molluscs throughout the world, some of which are associated with mass mortalities. Life cycle involves vegetative proliferation within the host, by which a cell named trophozoite undergoes successive bipartitioning. Other stages have been observed in vitro or in vivo, depending on the species: hypnospore, zoosporangium and zoospore. Molecular taxonomy supports a close affinity between dinoflagellates and Perkinsus spp. Six species of Perkinsus are currently considered valid: P. marinus, P. olseni, P. qugwadi, P. chesapeaki, P. andrewsi and P. mediterraneus. Histology and, above all, incubation of host tissues in Ray's fluid thioglycollate medium (RFTM) are classic diagnostic methods. In addition, more sensitive and quicker molecular diagnostic techniques based on either immunoassays or PCR have been developed for Perkinsus spp. Epizootiological studies have shown a marked influence of water temperature and salinity on P. marinus infection in oysters Crassostrea virginica, thus determining parasite geographical range and temporal disease dynamics (seasonality). In vitro cultures have been established for four Perkinsus spp. Immune response to infection varies depending on host and involves phagocytosis or encapsulation of the parasite cells by host haemocytes. A polypeptide is secreted by clam Tapes philippinarum haemocytes that could kill the parasite. In vitro cultured P. marinus cells secrete proteases that are likely involved in degradation of host tissues. P. marinus can suppress the toxic oxygen radicals produced by host haemocytes. In addition to host death, sublethal effects caused by Perkinsus spp. (reduction of fecundity, growth, and condition) may have significant ecological and economic implications. Various strategies have been assayed to mitigate the consequences of P. marinus epizootics on the oyster industry: modifications of management/culture procedures, selective breeding to obtain resistant oyster strains, and the use of triploid oysters and allochthonous oyster species. Some chemotherapeutants have been proved to inhibit or kill parasite cells in vitro.

Key words: Perkinsus / Bivalve molluscs / Taxonomy / Epizootiology / In vitro culture / Host-parasite interaction / Prophylaxis

Corresponding author: villalba@cimacoron.org

© EDP Sciences, IFREMER, IRD 2004

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