Marine Institute

Possible case of Bonamia Ostrea in Lough Foyle Oysters

June 7, 2005

The Marine Institute is investigating a potential case of Bonamia ostrea in a wild oyster bed in Lough Foyle. Bonamia ostrea is a microscopic single-celled parasite that affects flat oysters (Ostrea edulis) and has no impact either on other shellfish or on human health. While it does not affect the taste or edibility of the oyster in any way and poses no health risk to oyster consumers, it can result in mortalities in the affected oyster stocks.

This is the first possible isolation of the parasite in Lough Foyle. It was identified through the Marine Institute's routine monitoring programme when 13 out of 30 oysters sampled were identified as suspect positive for the parasite.  Slides have been sent to the Community Reference Laboratory (CRL) in France for confirmation. To date, they have confirmed the presence of a suspect organism. A further sample was taken from Lough Foyle and processed on the 2/6/05. Additional tissue was taken for confirmatory analysis this will be sent to the CRL today. This will allow the CRL to make a definitive identification and results are expected the week commencing the 13th June 2005.

Bonamia ostreae has a wide geographic distribution taking in sectors of both the east and west coasts of the USA, continental Europe and many parts of the English and Irish coastlines. Bonamia ostrea was first isolated in Ireland in 1987 and since then it has been isolated in a number of oyster beds around the coast. Currently, six Irish bays have been identified as being positive for Bonamia ostrea.

The only known method of natural disease transmission is oyster to oyster via the introduction of infected oysters to a previously uninfected area.  It is possible to transmit Bonamiosis experimentally in the laboratory by co-habitation and also by the inoculation of the purified parasite (Culloty et al, 1990). There is currently no known treatment. In order to prevent infected stocks being mixed with healthy stock, movement of shellfish species susceptible to Bonamia from affected bays to areas that are free from the parasite is prohibited.  All movements of shellfish within Ireland are strictly controlled by the Department of Communications, Energy and Natural Resources. 

The Marine Institute will be working with the relevant authorities in Northern Ireland to carry out an epidemiological study to ascertain how the disease may have entered Lough Foyle.

ENDS.