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Pathogens, parasites and diseases of pearl oysters Pinctada maxima in Northern Australian waters

Humphrey, J., Connell, M., Norton, J., Jones, B.ORCID: 0000-0002-0773-2007, Barton, M., Shelly, C. and Creeper, J. (1999) Pathogens, parasites and diseases of pearl oysters Pinctada maxima in Northern Australian waters. SPC Pearl Oyster Information Bulletin (13). p. 32.


A health survey, based primarily on gross and histopathological examinations of pearl oysters Pinctada maxima, was undertaken between 1994 and 1997 from Queensland, Northern and Western Australia. The study included 4767 mature animals with no history of disease from wild harvest and pearl culture farms, together with batches of spat for interstate movement and cases of diseased mature and juvenile oysters.

The study was undertaken to improve knowledge on diseases confronting the pearl oyster industry, to facilitate regional and national quarantine, to enhance diagnostic capabilities and to identify pathogenic agents for further investigation. The study established the occurrence, prevalence and distribution of a taxonomically diverse range of microbial, protozoan and metazoan agents associated with pearl oysters and evaluated the pathogenic significance of these agents. Over 57% of the mature oysters were normal and free from infectious agents, whilst many carried agents not considered significant pathogens.

Pathogenic or potentially pathogenic agents identified in apparently normal P. maxima included a papovalike virus of the palp, viral-like inclusion bodies in the digestive gland epithelium, rickettsiales-like agents in the digestive gland and gill, enigmatic protozoan-like bodies in the digestive gland, metazoa including copepods in the digestive gland, a copepod Anthessius pinctadae in the oesophagus and a Haplosporidian sp. in the digestive gland. Bivalve molluscs, sponges and polychaetes commonly invaded the shell matrix. Vibrio sp., the enigmatic protozoan-like agent and sub-optimal environmental conditions were associated with mortalities in mature and juvenile oysters. Differences in regional occurrence were evident with some agents, providing a basis for implementation of quarantine.

Normal histological criteria for P. maxima were established and host responses to injury described, providing a basis on which the normal structure of the pearl oyster may be differentiated from the structure altered by disease.

The study indicates that Australian P. maxima are relatively free of serious pathogens. At the same time, a need exists to clarify the taxonomic status and establish the pathogenic significance of a number of the agents recorded. The study provides baseline data on the occurrence and prevalence of potential pathogens and provides a basis for the diagnosis of infectious and non-infectious diseases of P. maxima.

Item Type: Journal Article
Publisher: Secretariat of the Pacific Community
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