Oyster diseases Bonamia ostreae, Bonamia exitiosa och Marteilia refringens
Marteilia refringens, Bonamia ostreae and Bonamia exitiosa are parasites that causes disease to European oyster (Ostrea edulis). Infection with M. refringens, B. ostreae and B. exitiosa are listed as category C disease. The diseases have never been detected on oysters in Sweden.
Sweden has a unique coastline. Along the coast around Sweden there is a clear salinity gradient, from almost completely fresh water in the northern Gulf of Bothnia via brackish water in the Baltic Sea to close to oceanic water with high salinity in the Skagerrak. Due to the variation in salinity European oysters can only be found on the west coast. The European oyster is the only susceptible species in Sweden to M. refringens, B. ostreae and B. exitiosa.
There are no imports of oysters from other countries for release in Swedish waters. Sampling of oysters takes place in accordance with the national monitoring plan.
Aquaculture establishments in Sweden receive regular animal health visits. Results from sampling are reported further down this page.
Infection with M. refringens, B. ostreae and B. exitiosa is notifiable. More information about notification obligations and the EU's listed diseases can be found at:
Infection with Bonamia ostreae and Bonamia exitiosa
Infection with B. ostreae and B. exitiosa has never been detected in Sweden.
European oyster (Ostrea edulis) is the only susceptible species in Sweden.
For more information:
- Bonamios hos ostron (sva.se) – in Swedish
- Bonamia sp. – EURL for Molluscs Diseases (eurl-mollusc.eu)
- Bonamia exitiosa: Appendix IX (woah.org)
- Bonamia ostreae: Appendix IX (woah.org)
Infection with Marteilia refringens
There are two types of Marteilia refringens: type M which is most often found in mussels and type O which is most often found in oysters. In the past, these two types have been seen as one species. However, research has recently concluded that these two types of M. refringens are two different species. Type M is in some contexts called Marteilia pararefringens.
European oyster (Ostrea edulis) is the only susceptible species in Sweden. M. refringens has never been detected on oysters in Sweden. M. refringens has been detected on blue mussel. The last time M. refringens was detected on blue mussel was in 2015. Blue mussel (Mytilus edulis) is not listed as a susceptible species for M. refringens.
- Marteilios hos ostron och blåmussla (sva.se)
- Marteilia refringens – EURL for Molluscs Diseases (eurl-mollusc.eu)
- Marteilia refringens: Appendix IX (woah.org)
Results from oyster sampling 2010–2022
The Swedish Veterinary Agency (SVA) has sampled European oysters (Ostrea edulis) on the west coast of Sweden since 2010. Below are summaries of SVA's investigation of Marteilia refringens, Bonamia ostreae and Bonamia exitiosa on European oysters.
Bonamia ostreae
Year | Number of molluscs in the sample | Diagnostic | Number of samples with positive results | Number of sampling points in the wild | Number of sampling points at establishment |
|---|---|---|---|---|---|
2010 | 90 | Histopathology | 0 | 3 | 0 |
2011 | 90 | 30 Histopathology and PCR 60 only histopathology | 0 | 1 | 2 |
2012 | 150 | Histopathology and PCR | 0 | 4 | 1 |
2013 | 150 | Histopathology and PCR | 0 | 3 | 2 |
2014 | 150 | Histopathology and PCR | 0 | 4 | 1 |
2015 | 120 | Histopathology and PCR | 0 | 2 | 2 |
2016 | 30 | Histopathology and PCR | 0 | 1 | 0 |
2017 | 150 | Histopathology and PCR | 0 | 2 | 3 |
2018 | 150 | Histopathology and PCR | 0 | 2 | 3 |
2019 | 150 | Histopathology and PCR | 0 | 2 | 3 |
2020 | 150 | Histopathology and PCR | 0 | 1 | 4 |
2021 | 150 | Histopathology and PCR | 0 | 5 | 0 |
2022 | 150 | Histopathology and PCR | 0 | 1 | 4 |
Bonamia exitosa
Year | Number of molluscs in the sample | Diagnostic | Number of samples with positive results | Number of sampling points in the wild | Number of sampling points at establishment |
|---|---|---|---|---|---|
2010 | 90 | Histopathology | 0 | 3 | 0 |
2011 | 90 | Histopathology | 0 | 1 | 2 |
2012 | 150 | Histopathology | 0 | 4 | 1 |
2013 | 150 | Histopathology | 0 | 3 | 2 |
2014 | 150 | Histopathology | 0 | 4 | 1 |
2015 | 120 | Histopathology | 0 | 2 | 2 |
2016 | 30 | Histopathology | 0 | 1 | 0 |
2017 | 150 | Histopathology | 0 | 2 | 3 |
2018 | 150 | Histopathology and PCR | 0 | 2 | 3 |
2019 | 150 | Histopathology and PCR | 0 | 2 | 3 |
2020 | 150 | Histopathology and PCR | 0 | 1 | 4 |
2021 | 150 | Histopathology and PCR | 0 | 5 | 0 |
2022 | 150 | Histopathology and PCR | 0 | 1 | 4 |
Marteilia refringens
Year | Number of molluscs in the sample | Diagnostic | Number of samples with positive results | Number of sampling points in the wild | Number of sampling points at establishment |
|---|---|---|---|---|---|
2010 | 90 | Histopathology and PCR | 0 | 3 | 0 |
2011 | 90 | 60 histopathology and PCR, | 0 | 1 | 2 |
2012 | 150 | Histopathology and PCR | 0 | 4 | 1 |
2013 | 150 | Histopathology and PCR | 0 | 3 | 2 |
2014 | 150 | Histopathology and PCR | 0 | 4 | 1 |
2015 | 120 | Histopathology and PCR | 0 | 2 | 2 |
2016 | 30 | Histopathology and PCR | 0 | 1 | 0 |
2017 | 150 | Histopathology and PCR | 0 | 2 | 3 |
2018 | 150 | Histopathology and PCR | 0 | 2 | 3 |
2019 | 150 | Histopathology and PCR | 0 | 2 | 3 |
2020 | 150 | Histopathology and PCR | 0 | 1 | 4 |
2021 | 150 | Histopathology and PCR | 0 | 5 | 0 |
2022 | 150 | Histopathology and PCR | 0 | 1 | 4 |
Legislation
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Revision date: 2024-03-22