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Update on Crayfish Plague in Ireland

21 Aug 2019

DNA analysis by the Fish Health Unit at the Marine Institute has confirmed the presence of crayfish plague in the following locations so far in 2019:

  • River Nore in Kilkenny City, Co. Kilkenny
  • River Maigue near Adare in Co. Limerick
  • River Clare near Claregalway in Co. Galway (based on testing of water samples taken in 2018)
  • River Slate near Rathangan in Co. Kildare

Further analyses are ongoing to establish if there may be any link between these and previous outbreaks of Crayfish plague.

Previous Outbreaks

Map of Crayfish Plague infected river catchments 20-08-2019. Click the map to download a full resolution version (3.3MB .pdf)

The first confirmed outbreak of crayfish plague occurred in 2015 in the Bruskey River, a tributary of the Erne. Subsequently in 2017, multiple outbreaks were confirmed, initially in the River Suir, then the River Deel, the River Barrow and also the Lorrha River in Co. Tipperary. A further three outbreaks were detected in 2018 in the Al River at Athlone; the Blackwater near Aughentaine, Co. Tyrone; and the River Barrow, upstream of the previous detection point in the same river from 2017.

Genotyping analysis by OIE reference laboratories in the UK and in Finland have shown there are at least 3 different genotypes of Aphanomyces astaci present in Ireland thus far. This genetic diversity of A. astaci suggests there have been at least 3 separate introductions of the disease into the country. This has highlighted an urgent need for a better understanding of the possible sources of the disease, its routes of transmission, and its current spread.

Further information on Crayfish Plague, including maps of the affected catchments, can be found on the Biodiversity Data Centre website here:

Biosecurity Measures

The spores of A. astaci can survive for several weeks and can be transported on damp equipment, boats, or machinery to other river and lake systems. Any site within an affected catchment should be considered high risk.

Anyone involved in activities in any watercourse should observe the ‘Check, Clean and Dry’ protocol once they leave the river and before visiting any waterway again.

This includes community and local authority clean-up groups, survey work as well as anglers and all recreational water uses. All wet gear (boats, clothing and equipment) should be checked for any silt or mud, plant material or animals before being thoroughly cleaned and finally dried. Disinfectant or hot water should be used to clean all equipment and this should be followed by a minimum 48 hour drying period (preferably longer up to a week).

The drying period is especially important as the infectious spores are destroyed by desiccation. Care should be taken with boats to ensure water is removed from the inside. The crayfish plague organism can be carried on wet equipment to new sites and spread to other unaffected populations in Ireland.

The apparent spread of Crayfish Plague in Ireland over the last few years highlights the need to observe the ‘Check, Clean and Dry’ protocol as matter of routine for all users of waterways in Ireland.


National Crayfish Plague Surveillance Programme

In an effort to assess the prevalence of Aphanomyces astaci nationally and investigate the potential presence of non-native crayfish species which may have introduced the pathogen into Ireland; the National Crayfish Plague Surveillance Programme, jointly funded by National Parks & Wildlife Service (NPWS) & Marine Institute, was established in 2018.

This surveillance programme uses the latest environmental (e)DNA methodologies to detect the presence of Aphanomyces astaci in water from selected sample points in all catchments/sub-catchments where white-clawed crayfish are known to be present (34 areas in total).

The first phase of sampling for the surveillance programme ran from August 2018 until December 2018 to coincide with the crayfish moulting/reproduction season. Sample collection involves collecting water samples from 6 sampling sites on each of the 34 catchments. Water samples are then filtered on site and these filters are frozen for subsequent analysis using eDNA technology.

Further details on the National Crayfish Plague Surveillance Programme can be requested from