Synopsis of Infectious Diseases and Parasites of Commercially Exploited Shellfish

This document was derived from Bower, S.M., McGladdery, S.E., Price, I.M. (1994). Synopsis of infectious diseases and parasites of commercially exploited shellfish. Annual Review of Fish Diseases 4: 1-199 and subsequently updated.

On this page

• Abstract
• Introduction
  • Definitions of Category
  • Organization of Summaries
  • References for the Introduction
• Table of Contents
  • Diseases and Pathogens of Molluscan Shellfish
    • Oysters
    • Mussels
    • Clams & Cockles
    • Scallops
    • Abalone
  • Diseases and Pathogens of Echinoderms
    • Sea Urchins
    • Sea Stars
  • Diseases and Pathogens of Crustacea
    • Lobsters
    • Shrimp & Prawns
    • Crabs
    • Crayfish

Introduction

The rapidly increasing development of shellfish aquaculture around the world, along with an expanding market demand for fresh (live) shellfish, have escalated the need for vigilance against the spread of shellfish diseases. The risks associated with uncontrolled transfer and introduction of live aquatic organisms have long been recognised (ICES 1988), especially for finfish species which are regularly transferred from one location to another. In the last 10-20 years the frequency of shellfish transfers has also increased, due, in part, to the development of hatchery-based seed production and remote setting, as well as to increasing use of non-indigenous species in aquaculture. Concomitant with this increase in transfer has been the spread of significant shellfish diseases around the world, such as Bonamia ostreae of flat (= European, edible or Belone) oysters, Ostrea edulis from North America to France and subsequently throughout most of the Atlantic coast of Europe (Sindermann 1991).

Recognition of the correlation between shellfish transfers and disease-spread has been reflected by global development of regulations or guidelines to control live imports of shellfish (mainly molluscs and shrimps) (Sindermann 1986, ICES 1988, Anon. 1991, Brock 1992, Carey 1992, Carlton 1992, Smith 1992). In Canada, this led to the development of the National Aquatic Animal Health Program that is co-delivered by the Canadian Food Inspection Agency (legislative and regulatory lead) and Fisheries and Oceans Canada (diagnostic testing and research).

In order to have: 1) a strong scientific reference base upon which to justify the Regulations for shellfish, 2) classify the disease agents according to a level of concern, and 3) develop appropriate sampling protocols, an extensive list of shellfish diseases was compiled. Drawing upon the primary literature and other information that is often not readily available (i.e., research laboratory reports, government technical reports, and personal communications with colleagues) a comprehensive, worldwide synopsis on shellfish diseases of commercially important molluscs, echinoderms and crustaceans was developed. This synopsis was designed to be a source of basic information, including key references to pertinent literature, which could be used as part of the decision-making process in regard to concerns relevant to shellfish health issues. Also, it was created to be inclusive by incorporating shellfish species both present in and absent from Canadian waters. However, it is not the aim of this synopsis to review all of the details of each of the infectious agents nor does it include organisms described from shellfish of little or no current economic value. We refer readers to the key references listed after each summary and to volumes edited by Kinne (1983, 1990) and Sparks (1985) (see References) for an in depth review of the literature on shellfish including those that are not commercially exploited. Nevertheless, we have endeavoured to cover most organisms (pathogenic and non-pathogenic) of commercially important shellfish species in as broad a scope as possible.

This synopsis is arranged with each disease/parasite summary on its own page such that it is accessible as a single unit. All summary pages are listed in the Table of Contents and grouped firstly by shellfish host type (e.g., oysters), and within that, the parasites and pathogens are arranged according to their Category status in Canada (see Definitions of Category). Within each Category grouping, the summary pages are arranged by type (i.e. all viruses are together, as are all bacteria etc.). Thus, in the Table of Contents, known infectious diseases and parasites of oysters are listed in the subsection "Oysters" of the section entitled "Diseases and Pathogens of Mollusca". The other subsections included in the "Diseases and Pathogens of Mollusca" are: Mussels, Clams & Cockles, Scallops, and Abalone. Likewise, the "Diseases and Pathogens of Echinoderms" section includes subsections Sea Urchins and Sea Stars. The subsections of "Diseases and Pathogens of Crustacea" are Lobsters, Shrimp & Prawns, Crabs, and Crayfish. Each of these subsections encompasses infectious diseases known to affect that group. Each disease/parasite summary page is accessible via the Table of Contents and the organization pattern used in summary pages is described on a separate page (see Organization of Summaries).

Definitions of Category

Each disease agent of shellfish has been assigned to a Category with respect to current shellfish health conditions in Canada. The Category was assigned according to the following definitions:

Category 1

Agents of infectious diseases which have not been detected in Canada, but the shellfish host species of which are found in Canada. Because these diseases can have serious impact on shellfish stocks, the disease agents responsible must be kept out of Canada.

Category 2

Agents of infectious diseases which have a limited geographic distribution within Canada. Because these diseases can have serious impact on shellfish health, these agents must be prevented from spreading to regions or provinces where they are not known to occur. Importation of shellfish between regions or provinces must be guided by the principle that the importation will not result in the introduction of a disease agent not already known to occur in the receiving region or province.

Category 3

Agents of infectious diseases whose host species do not presently occur in Canada. When similar agents are listed for host species already present in Canadian waters, these agents are not assumed to be identical to those present in the non-indigenous hosts. Therefore, if a host for a Category 3 disease agent is discovered in or becomes introduced into Canada, the disease agent automatically will be moved to Category 1 status.

Category 4

Agents of infectious diseases which have negligible or questionable significance in Canada because:

1. they cause no significant pathology or
2. the pathological condition is related to husbandry

Detection of a Category 4 disease agent does not imply restriction on importation into Canada or on movement within Canada.

Organization of Summaries

The summary of each infectious disease agent, parasite, or a group of closely related infectious organisms, is organized into nine sections:

1. Category (with respect to current health conditions in Canada)
2. Common, generally accepted names of the organism or disease agent
3. Scientific name or taxonomic affiliation
4. Geographic distribution
5. Host species
6. Impact on the host
7. Diagnostic techniques
8. Methods of control
9. References

When two or more species of closely related infectious agents or parasites within one summary have different geographic distributions, host species, impact on the host(s), diagnostic technique and/or methods of control, applicable sections within that summary were subdivided into a, b, and c. Thus, all similarly lettered subsections within a summary pertain to the same organism(s).

Diagnostic techniques are presented in the following order: Gross Observations, Squash Preparations, Wet Mounts, Whole Mounts, Smears, Histocytology, Tissue Imprints, Histology, Electron Microscopy, Immunological Assay, DNA Probes, Culture, Bioassay,and Digestion. Occasionally, a category called Further Research is included if current research activities are directed towards the development of improved techniques. If techniques are either not applicable to, or not described for, the organism under discussion, no data are provided. Appropriate illustrations for most organisms can often be found in one or more of the key references listed.

References for the Introduction

• Anon. 1991. National Report for Canada: 1990-91 on Introduction and Transfer of Marine Organisms. Submitted to ICES Working Group on Introductions and Transfers of Marine Organisms, Helsinki, Finland, June 5-7, 1991, 12pp.
• Brock, J.A. 1992. Procedural requirements for marine species introductions into and out of Hawaii. pp. 51-53. In De Voe, R. [ed.]. Proceedings of the Conference & Workshop: Introductions & Transfers of Marine Species - Achieving A Balance Between Economic Development and Resource Protection. South Carolina Sea Grant Consortium, October 30 - November 2, 1991. Hilton Head Island, South Carolina.
• Carey, T.G. 1992. Federal and provincial policies for marine species introductions and transfers in Atlantic Canada. pp. 43-46. In De Voe, R. [ed.]. Proceedings of the Conference & Workshop: Introductions & Transfers of Marine Species - Achieving A Balance Between Economic Development and Resource Protection. South Carolina Sea Grant Consortium, October 30 - November 2, 1991. Hilton Head Island, South Carolina.
• Carlton, J.T. 1992. An international perspective on species introductions: The ICES Protocol. pp. 31-33. In De Voe, R. [ed.]. Proceedings of the Conference & Workshop: Introductions & Transfers of Marine Species - Achieving A Balance Between Economic Development and Resource Protection. South Carolina Sea Grant Consortium, October 30 - November 2, 1991. Hilton Head Island, South Carolina.
• ICES 1988. Codes of Practice and Manual of Procedures for Consideration of the Introductions and Transfers of Marine and Freshwater Organisms. Cooperative Research Report 159. G.E.Turner [ed.]. [Prepared jointly with the EIFAC Working Partyon Introductions (EIFAC publication as EIFAC Occasional Paper No. 23, 44 pp., 1988)].
• Kinne, O. [ed.]. 1983. Diseases of Marine Animals. Volume II: Introduction, Bivalvia to Scaphopoda. Biologische Anstalt Helgoland, Hamburg. 571 p.
• Kinne, O. [ed.]. 1990. Diseases of Marine Animals. Volume III: Introduction, Cephalopoda, Annelida, Crustacea, Chaetognatha, Echinodermata, Urochordata. Biologische Anstalt Helgoland, Hamburg. 696 p.
• Sindermann, C.J. 1986. Strategies for reducing risks from introductions of aquatic organisms: a marine perspective. Fisheries 11(2): 10-15.
• Sindermann, C.J. 1991. Case histories of effects of transfers and introductions on marine resources: Introduction. Journal de Conseil d’Exploration de la Mer 47: 377-378.
• Smith, T.I.J. 1992. (Moderator) International, national and regional strategies for managing marine species introductions and transfers. In De Voe, R. [ed.]. Proceedings of the Conference & Workshop: Introductions & Transfers of Marine Species - Achieving A Balance Between Economic Development and Resource Protection. South Carolina Sea Grant Consortium, October 30 - November 2, 1991. Hilton Head Island, South Carolina.
• Sparks, A.K. 1985. Synopsis of Invertebrate Pathology Exclusive of Insects. Elsevier Science Publishing Co., Amsterdam. 423 p.

Additional references pertaining to Introduction:

• Andrews, J.D. 1980. A review of introductions of exotic oysters and biological planning for new importations. Marine Fisheries Review, December 1980: 1-11.
• Bachère, E., E. Mialhe, D. Noël, V. Boulo, A.Morvan and J. Rodriguez. 1995. Knowledge and research prospects in marine mollusc and crustacean immunology. Aquaculture 132: 17-32.
• Kern, F.G. 1994. Research strategies and protocols established for international molluscan shellfish introductions. Proceedings of the Conference & Workshop, Nonindigenous Estuarine & Marine Organisms (NEMO). Seattle, Washington, April 1993. NOAA, U.S. Department of Commerce. pp. 85-92.
• Reddington, J. 1995. Advanced diagnosis: you can't wage war if you don't know your enemy. Bulletin of the Aquaculture Association of Canada 95-2(2): 17-19.

Date last revised: June 2001

Citation Information

Bower, S.M. (2010): Synopsis of Infectious Diseases and Parasites of Commercially Exploited Shellfish.

Date last revised: March 2010

Bower, S.M., McGladdery, S.E. (2014): Synopsis of Infectious Diseases and Parasites of Commercially Exploited Shellfish: Abstract.

Date last revised: November 2014