Disease data

Bonamiosis

Previously listed diseases
Molluscs
Protozoan disease; Haplosporidia; Bonamia spp.

Summary from the online OIE Diagnostic Manual

Bonamiosis here refers only to the diseases in oysters caused by Bonamia ostreae in the Northern Hemisphere, and by Bonamia exitiosus and Mikrocytos roughleyi in the Southern Hemisphere. If detected outside the known range of Mikrocytos roughleyi and Bonamia spp., electron microscopy or DNA-based assays, when available, must be used to identify and distinguish the detected organism from other microcell species (Bonamia ostreae, Bonamia exitiosus , Mikrocytos mackini and M. roughleyi). The presence of these pathogens in any bivalve should be regarded as potentially serious and the OIE Reference Laboratory should be consulted.

Bonamiosis is caused by the haplosporidians Bonamia ostreae, B. exitiosus and Mikrocytos roughleyi( 3-5, 8, 11, 17, 21 ) . Bonamiosis is also known as microcell disease, haemocyte disease of flat oysters (B. ostreae), haemocyte disease of dredge oysters (Bonamia exitiosus) or winter mortality (Mikrocytos roughleyi).

Bonamia ostreae occurs naturally in Ostrea edulis and O. conchaphila (= O. lurida), and can infect O. puelchana, O. angasi and Ostrea chilensis (= Tiostrea chilensis, T. lutaria) when moved into endemic zones ( 12, 13, 20 ) . Bonamia exitiosus occurs in O. angasi, O. denselammellosa and T. chilensis( 8 ) . Species of Ostrea and Tiostrea and other ostreids (Crassostrea rivularis = C. arakensis)( 6 ) should be considered to be potentially susceptible to Bonamia spp. Mikrocytos roughleyi infects the Sydney rock oyster Saccostrea glomerata (commercialis).

The geographical distribution of B. exitiosus is: New Zealand ( around South Island and lower North Island )( 9 ) and Australia ( Western Australia, Victoria and Tasmania ) . Bonamia ostreae has been reported from France, Ireland, Italy, the Netherlands, Spain, the United Kingdom ( excluding Scotland ) , and the United States of America ( California, Maine and Washington State )( 2, 10, 18, 19, 22, 23 ) , but is now thought to be absent from Denmark. Mikrocytos roughleyi occurs in New South Wales, Australia.

Bonamiosis is a lethal infection of the haemocytes of flat oysters, sometimes accompanied by yellow discoloration and extensive lesions on the gills and mantle ( 21 ) . However, most of the infected oysters appear normal. Lesions occur in the connective tissue of the gills, mantle, and digestive gland. These intrahaemocytic protistans quickly become systemic with overwhelming numbers of parasites coinciding with the death of the oysters. In highly susceptible hosts, bonamiosis is a lethal infection of the haemocytes. Some evidence suggests that the pathology caused by Bonamia spp. depends on which host species and population is infected. For example, B. exitiosus in oysters from Tasmania were highly epitheliotropic and associated with focal abscesses in some populations without evidence of systemic spread. Mikrocytos roughleyi is associated with focal abcess-type lesions in the gill, connective and gonadal tissues and alimentary tract ( 11 ) . It induces a systemic intracellular infection in the haemocytes ( but never in the connective tissue cells ) .

Bonamia spp. may occur throughout the year, but prevalence and intensity of infection tend to increase during the warm season ( 7, 12, 15 ) . There is a seasonal variation in infection by B. ostreae with the highest prevalence occurring in September in the Northern Hemisphere. In the Southern Hemisphere, B. exitiosus shows the highest prevalence from January to April with the parasite being barely detectable in September and October. The prepatent period for B. ostreae and B. exitiosus is usually 3-4 months but can be up to 5 months. In the Southern Hemisphere, the disease caused by M. roughleyi is associated with low temperatures and high salinities. It can kill up to 70% of mature Sydney rock oysters in their third winter before marketing, and has a prepatent period of 2.5 months ( 11 ) .

Bonamiosis can be transmitted experimentally by cohabitation or inoculation ( 14 ) .

Examination of stained tissue sections and tissue imprints of susceptible organs are the recommended methods for screening ( 1, 24 ) . For diagnosis, the recommended guidelines for sampling are those stated in Chapter 1.1.4 and Chapter I.2. of this Aquatic Manual . However, the disease may be not detectable by the usual methods during the first 5 months of infection.

Countries affected

Country Year Status View Records
Australia 2005 Reported present in specific zones View Records
Canada 2005 Reported present in specific zones View Records
France 2005 Reported present in specific zones View Records
Ireland 2005 Reported present in specific zones View Records
Italy 2003 Reported present or known to be present View Records
Kuwait 2003 Year of last reported occurrence View Records
Morocco 2005 Reported present or known to be present View Records
Netherlands 2005 Reported present or known to be present View Records
New Zealand 2005 Reported present in specific zones View Records
Spain 2005 Reported present in specific zones View Records
UK/ Great Britain 2005 Reported present in specific zones View Records
United Kingdom 2006 Reported present or known to be present View Records
United States of America 2005 Serological evidence and/or isolation of causative agent, no clinical disease View Records

Species affected

Species Disease occurence Abstract
Crassostrea ariakensis Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases (3rd edition).
Crassostrea ariakensis Natural occurrence World Animal Health in 1998. Part 1. Reports on the animal health status and disease control methods.
Ostrea angasi Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases (3rd edition).
Ostrea angasi Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases 2003 (4th edition).
Ostrea chilensis Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases (3rd edition).
Ostrea denselammellosa Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases (3rd edition).
Ostrea denselammellosa Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases 2003 (4th edition).
Ostrea edulis Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases (3rd edition).
Ostrea edulis Natural occurrence World Animal Health in 1997. Part 1. Reports on the animal health status and disease control methods.
Ostrea edulis Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases 2003 (4th edition).
Ostrea lurida ( = O. conchaphila) Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases (3rd edition).
Ostrea lurida ( = O. conchaphila) Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases 2003 (4th edition).
Ostrea puelchana Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases (3rd edition).
Saccostrea ( =Crassostrea ) commercialis Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases 2003 (4th edition).
Tiostrea chilensis ( = T. lutaria ) Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases 2003 (4th edition).

Countries affected

Country Year Status View Records
Australia 2005 Reported present in specific zones View Records
Canada 2005 Reported present in specific zones View Records
France 2005 Reported present in specific zones View Records
Ireland 2005 Reported present in specific zones View Records
Italy 2003 Reported present or known to be present View Records
Kuwait 2003 Year of last reported occurrence View Records
Morocco 2005 Reported present or known to be present View Records
Netherlands 2005 Reported present or known to be present View Records
New Zealand 2005 Reported present in specific zones View Records
Spain 2005 Reported present in specific zones View Records
UK/ Great Britain 2005 Reported present in specific zones View Records
United Kingdom 2006 Reported present or known to be present View Records
United States of America 2005 Serological evidence and/or isolation of causative agent, no clinical disease View Records

Species affected

Species Disease occurence Abstract
Crassostrea ariakensis Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases (3rd edition).
Crassostrea ariakensis Natural occurrence World Animal Health in 1998. Part 1. Reports on the animal health status and disease control methods.
Ostrea angasi Natural occurrence Ostrea angasi acclimatization to French coasts.
Ostrea angasi Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases (3rd edition).
Ostrea angasi Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases 2003 (4th edition).
Ostrea chilensis Experimental demonstration Results of the acclimatization experiments of Ostrea chilensis on the Brittany coasts.
Ostrea chilensis Natural occurrence The annual pattern of infection by Bonamia sp. in New Zealand flat oysters, Tiostrea chilensis.
Ostrea chilensis Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases (3rd edition).
Ostrea denselammellosa Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases (3rd edition).
Ostrea denselammellosa Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases 2003 (4th edition).
Ostrea edulis Experimental demonstration Experimental contamination of Ostrea edulis Linne by Bonamia ostreae (Pichot et al., 1979) in Crach River (Morbihan).
Ostrea edulis Natural occurrence Bonamiasis: a model study of diseases in marine molluscs.
Ostrea edulis Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases (3rd edition).
Ostrea edulis Natural occurrence World Animal Health in 1997. Part 1. Reports on the animal health status and disease control methods.
Ostrea edulis Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases 2003 (4th edition).
Ostrea edulis Natural occurrence Research on Bonamia ostreae gen. n., sp. n., a new parasite of the flat oyster Ostrea edulis L.
Ostrea edulis Unknown Bonamia ostreae present in flat oysters (Ostrea edulis) does not infect mussels (Mytilus galloprovincialis).
Ostrea lurida ( = O. conchaphila) Natural occurrence Synopsis of infectious disease and parasites of commercially exploited shellfish.
Ostrea lurida ( = O. conchaphila) Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases (3rd edition).
Ostrea lurida ( = O. conchaphila) Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases 2003 (4th edition).
Ostrea puelchana Experimental demonstration Testing of the Argentina oyster, Ostrea puelchana, in several French oyster farming sites.
Ostrea puelchana Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases (3rd edition).
Saccostrea ( =Crassostrea ) commercialis Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases 2003 (4th edition).
Tiostrea chilensis ( = T. lutaria ) Experimental demonstration Bonamia ostreae infecting Ostrea lutaria in the U.K.
Tiostrea chilensis ( = T. lutaria ) Natural occurrence OIE Diagnostic Manual for Aquatic Animal Diseases 2003 (4th edition).