Aphanomyces astaci



Conservation status

Not Assessed

Native status


First reported in the wild



Invasive species - risk of High Impact

Irish status


Introduction pathways - 1

Transport Contaminant

Introduction pathways subclass - 1

Parasites on animals

Introduction pathways - 2

Transport Stowaway

Introduction pathways subclass - 2

Angling/fishing equipment

Invasive score


NAPRA Ireland risk assessed


Species Biology


Presence of the disease is generally identified by the presence of black (melanised) spots on crayfish but microscopic (Cerenius et al., 1992) or increasingly DNA techniques are used to confirm identification (Schrimpf et al., 2013). Anphanomyces astaci is a pseudofungus consisting of vegetative hyphae 7-9µm in width.


Causes widespread mortality in native crayfish species and has resulted in virtual extermination of all 5 native crayfish species in Europe with only relict populations surviving (Alderman, 2009). Loss of crayfish from Irish lakes are likely to result in changes in the macroinvertebrate community and an increase in the growth of dominant aquatic macrophytes (plant species large enough to be seen with the naked eye) (Matthews & Reynolds, 1992), however these impacts are likely to be exacerbated by the presence of non-native freshwater species that were not present in Ireland in 1992.


Inland surface waters


Releases tiny spores 9-11µm in diameter and are relatively few, 15-30 per sporangium (Alderman & Polglase, 1986). While optimal temperatures for sporangial formation and discharge lie between 16 and 24°C, it may occur at temperatures as low as 4°C (Alderman & Polglase, 1986).

Pathway and vector description

Originally introduced into Europe with North American crayfish species (Orconectes limosus spiny cheek, Pacifastacus leniusculus signal & Procambarus clarkii red swamp) in the 19th century (Alderman, 2009). The likely source of the 2015 introduction is unknown but thought to be from contaminated wet equipment, incorrectly decontaminated after being used in affected waters in Britain or Europe or by the introduction of non-native crayfish species (DAHG, 2015).

Mechanism of impact


Broad environment


Habitat description

All non-native North American freshwater crayfish can act as hosts for this disease (Alderman, 2009).

Species group


Native region

North America


World distribution(GBIF)

Irish distribution

Occasionally present

Crayfish plague was  confirmed from the River Bruskey in Co. Cavan in 2015 where it has been causing crayfish kills since then but is expected to die-out from the river when the last White-clawed crayfish are dead. Crayfish plague was confirmed from the River Suir between Clonmel and Carrick-on-Shannon, Co. Tipperary and from the River Deel near Rathkeale, Co. Limerick in 2017. All three river systems are being monitored for spread of the plague. See:

Crayfish plague was first diagnosed in Westmeath in Irish stocks of White-clawed crayfish from  a midlands limestone lake and crayfish farm in October, 1987  (Matthew & Reynolds, 1992).

If introduced on non-native crayfish the species can be considered established in Ireland but if introduced with contaminated equipment there is the potential for containment as spores only remain viable in water for approximately 6-9 days after death of an infected crayfish (Matthews & Reynolds, 1990).

Native distribution

Originally native to North America it has been introduced into Europe and Turkey (Alderman, 2009).

Temporal change

Date of first record category


Fifty year date category


Records submitted to Data Centre in 2022

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How can you help

Report any sightings of dead or diseased crayfish to the National Biodiversity Data Centre or Inland Fisheries Ireland. Practice good biosecurity by disinfecting and thoroughly drying any boating, fishing, angling or other equipment that has been used in British or continental European waters.

Further information

Delivering Alien Invasive Species In Europe (DAISIE) project list the crayfish plague as one of the 100 Worst Invaders in Europe. The Invasive Species Specialist Group (ISSG) of the SSC (Species Survival Commission) of the IUCN (International Union for Conservation Nature) consider the crayfish plague one of its 100 Worst Invaders globally.



Alderman, D. J., & Polglase, J. L. (1986). Aphanomyces astaci: isolation and culture. Journal of Fish Diseases, 9(5), 367-379.

Cerenius, L., Rufelt, S., & Söderhäll, K. (1992). Effects of Ampropylfos (RS)-1-aminopropylphosphonic acid) on zoospore formation, repeated zoospore emergence and oospore formation in Aphanomyces spp. Pesticide science, 36(3), 189-194.

Department of Arts, Heritage and the Gaeltacht (2015). Investigation underway into cause of Crayfish Plague on River Bruskey, near Ballinagh, Co Cavan. Press release prepared by Inland Fisheries Ireland, NPWS & NBDC.

Matthews, M., & Reynolds, J. D. (1990). Laboratory investigations of the pathogenicity of Aphanomyces astaci for Irish freshwater crayfish. Hydrobiologia, 203(3), 121-126.

Matthews, M., & Reynolds, J. D. (1992). Ecological impact of crayfish plague in Ireland. Hydrobiologia, 234(1), 1-6.

Schrimpf, A., Chucholl, C., Schmidt, T., & Schulz, R. (2013). Crayfish plague agent detected in populations of the invasive North American crayfish Orconectes immunis (Hagen, 1870) in the Rhine River, Germany. Aquatic Invasions, 8(1), 103-109.

DAISIE Factsheet 

 CABI - Datasheet

Global Invasive Species Database

Additional comments

Detailed description of biology, reproduction and culture of A. astaci in Alderman & Polglase (1986).