Ephemeral detection of Bonamia exitiosa (Haplosporida) in adult and larval European flat oysters Ostrea edulis in the Solent, United Kingdom

Luke Helmer, Chris Hauton, Tim Bean, David Bass, Ian Hendy, Eric Harris-Scott, Joanne Preston*

*Corresponding author for this work

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The haplosporidian parasite Bonamia exitiosa was detected using PCR in four adult and six larval brood samples of the European flat oyster Ostrea edulis from the Solent, UK. This represents the second reported detection of this parasite along the south coast of England. Adult oysters were collected and preserved from seabed populations or restoration broodstock cages between 2015 - 2018. The larvae within brooding adults sampled during 2017 and 2018 were also preserved. Molecular analysis of all samples was performed in 2019. The DNA of B. exitiosa was confirmed to be present within the gill tissue of one oyster within the Portsmouth wild fishery seabed population (n = 48), sampled in November 2015; the congeneric parasite Bonamia ostreae was not detected in this individual. This is the earliest record of B. exitiosa in the Solent. Concurrent presence of both B. ostreae and B. exitiosa, determined by DNA presence, was confirmed in the gill and heart tissue of three mature individuals from broodstock cages sampled in October 2017 (n = 99), two from a location on the River Hamble and one from the Camber Dock in Portsmouth Harbour. B. exitiosa was not detected in the November 2018 broodstock populations. A total of six larval broods were positive for B. exitiosa, with five also positive for B. ostreae. None of the brooding adults were positive for B. exitiosa suggesting that horizontal transmission from the surrounding environment to the brooding larvae is occurring. Further sampling of broodstock populations conducted by the Fish Health Inspectorate at the Centre for Environment, Fisheries and Aquaculture Science in June 2019 did not detect infection of O. edulis by B. exitiosa. These findings together suggest that the pathogen has not currently established in the area.
Original languageEnglish
Article number107421
Number of pages8
JournalJournal of Invertebrate Pathology
Early online date6 Jun 2020
Publication statusPublished - 1 Jul 2020


  • Oyster
  • Ostrea edulis
  • Bonamia exitiosa
  • Bonamia ostreae
  • Molecular diagnosis
  • Haplosporida


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