Pathogenicity of Vibrio tapetis, the etiological agent of brown ring disease in clams

Diseases of Aquatic Organisms

Christine Paillard¹  Susan E. Ford¹  Bassem Allam¹ 

关键词: Bivalve;    Bacteria;    Mortality;    Disease progression;    Immunofluorescence;    Enzyme-linked immunosorbent assay;   

DOI  :  10.3354/dao048221

学科分类：生物科学（综合）

来源: Inter-Research

【 摘 要 】

ABSTRACT: Brown ring disease (BRD) causes high mortalities in the introduced Manila clam Ruditapes philippinarum cultured in western Europe. The etiological agent of BRD, Vibrio tapetis, adheres to and disrupts the production of theperiostracal lamina, causing the anomalous deposition of periostracum around the inner shell. Because the primary sign of BRD is found outside the soft tissues, the processes leading to death are not as obvious as those for internal pathogens. This studywas designed to evaluate the pathogenicity of V. tapetis, in an attempt to help explain the mechanisms of mortality. We found high mortalities (up to 100%) for clams following the inoculation of V. tapetis into the extrapallial space(between mantle and inner shell) or the posterior adductor muscle of healthy R. philippinarum. Microscopy and immunological detection methods showed that the pathogen was rapidly eliminated from tissues and hemolymph of animals that survived theinoculation. In clams that died, the bacteria were found to have proliferated, resulting in severe tissue disruption. Bacteria were able to penetrate into tissues from the extrapallial space through the external epithelium of the mantle. In contrast, nomortalities were observed following injection of V. tapetis in the native European clam Ruditapes decussatus, which is resistant to BRD. This clam rapidly eliminated the bacterium from hemolymph and soft tissues. Clam mortality associatedwith BRD in the field is likely to result from the penetration of V. tapetis into the clam¹s extrapallial space through the disrupted periostracal lamina and from there into the soft tissues through the irritated mantle epithelium. Some bacteriaalso penetrate through the digestive epithelia. In either case, bacteria proliferate rapidly in the soft tissues, causing severe damage and subsequent death.

【 授权许可】

Unknown