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Crayfish plague
Sporangia and hyphae
Scientific classification
Domain:	Eukaryota
Clade:	Diaphoretickes
Clade:	SAR
Clade:	Stramenopiles
Phylum:	Oomycota
Order:	Saprolegniales
Family:	Leptolegniaceae
Genus:	Aphanomyces
Species:	A. astaci
Binomial name
Aphanomyces astaci Schikora, 1906

Crayfish plague (Aphanomyces astaci) is a water mold that infects crayfish, most notably the European Astacus which dies within a few weeks of being infected. When experimentally tested, species from Australia, New Guinea and Japan were also found to be susceptible to the infection.

Morphology

Crayfish plague invades tissue with hyphae. The hyphae develop sporangia that release amoeboid primary spores, which develop into flagellated secondary zoospores after encystment. The secondary zoospores have two flagella each and can repeatedly encyst before finally reaching a host, attaching and germinating.

History

Crayfish plague first arrived in Europe in Italy in 1859, either with imported crayfish from North America, or in ballast water discharge. After its original introduction in Italy in 1860, it spread quickly through Europe and was discovered in Sweden in 1907, in Spain in 1972, in Norway in 1971, in Great Britain in 1981, in Turkey in 1984 and in Ireland in 1987.

In 1959, to bolster dwindling stocks of native crayfish, the signal crayfish was introduced to Sweden. The signal crayfish was known to be resistant, and it was not recognised at that time that it was a carrier of the disease. In 2015, after 150 years of contact, no resistance had been discovered in native European crayfish. But during later years, some populations that apparently have achieved different levels of resistance have been discovered.

This species was studied and named by the German Mycologist Friedrich Schikora (1859–1932), from a type specimen in Germany in 1906.

Transmission

Transport of signal crayfish, red swamp crayfish and infected native European freshwater crayfish between waters is the main cause of contamination, though the disease can also be spread via items that have been in contact with contaminated water, such as a fishing tackle or footwear. The spores are sensitive to high or low temperatures. Most authorities have local rules and regulations to minimize the movement of water between different waterbodies (in for example a boat), and recommend that crayfish used as bait should come from the same water as that being fished, or should be frozen to at least −10 °C (14 °F) for one day before use, if there is a risk of contamination. The spores of crayfish plague disappear from an infected water system (connected lakes and rivers) within a few weeks once the last infected crayfish is removed. Reintroduction is then possible, as long as no infected waters are in contact with the lake.

Signs

Infection with Aphanomyces astaci is accompanied by few signs in its early stages, and the first indication of infection may be mortality. In the later stages, the muscles of the tail may appear whitened, or brownish-red where blood cells have encapsulated the hyphae. The effects of the neurotoxins in the oomycete can include appearing in daytime (crayfish are typically nocturnal) and a lack of coordination.

References

1. Paul Kirk (2010). "Aphanomyces astaci Schikora, 1906". World Register of Marine Species. Retrieved June 29, 2011.
2. Susan M. Bower (June 28, 2006). "Crayfish plague (fungus disease)". Synopsis of Infectious Diseases and Parasites of Commercially Exploited Shellfish. Fisheries and Oceans Canada. Archived from the original on December 12, 2008. Retrieved June 29, 2011.
3. WOAH Aquatic Animal Health Standards Commission (2024). "Chapter 2.2.2. - Infection with Aphanomyces astaci (Crayfish Plague)" (PDF). Manual of Diagnostic Tests for Aquatic Animals (11 ed.). World Organization for Animal Health. Retrieved 6 October 2024.
4. Vrålstad, Trude; Johnsen, Stein I.; Taugbøl, Trond (2011). "NOBANIS – Invasive Alien Species Fact Sheet – Aphanomyces astaci" (PDF). Online Database of the European Network on Invasive Alien Species – NOBANIS. Retrieved 10 October 2024 – via Invasives.ie, Invasive Species in Ireland.
5. ^ Christian Nellemann & Emily Corcoran, ed. (2010). "Restoration of a depleted crayfish fishery in Europe – lessons learnt". Dead Planet, Living Planet: Biodiversity and Ecosystem Restoration for Sustainable Development (PDF). UNEP / Earthprint. pp. 90–91. ISBN 978-82-7701-083-0. Archived from the original on 2017-02-07. Retrieved 2011-06-29.
6. Kei Westman (2002). "Alien crayfish in Europe: negative and positive impacts and interactions with native crayfish". In Erkki Leppäkoski, Stephan Gollasch & Sergej Olenin (ed.). Invasive Aquatic Species of Europe: Distribution, Impacts, and Management. Springer. pp. 76–95. ISBN 978-1-4020-0837-5.
7. David Alderman (December 18, 2006). "Aphanomyces astaci" (PDF). Delivering Alien Invasive Species Inventories for Europe. Archived from the original (PDF) on September 24, 2015. Retrieved June 29, 2011.
8. María Martínez-Ríos; et al. (December 18, 2006). "Resistance to Crayfish Plague: Assessing the Response of Native Iberian Populations of the White-Clawed Freshwater Crayfish". Journal of Fungi. 8 (4): 342. doi:10.3390/jof8040342. PMC 9025747. PMID 35448573.
9. ^ "Crayfish plague". Environment Agency. June 2, 2011. Archived from the original on September 21, 2008. Retrieved June 29, 2011.
10. ^ Nicky Buller (September 2008). "Crayfish Plague" (PDF). Australia and New Zealand Standard Diagnostic Procedure. Sub-Committee on Animal Health Laboratory Standards. Archived from the original (PDF) on 2015-03-11. Retrieved 2015-06-26.

External links

• "Crayfish plague". Environment Agency. June 2, 2011.
• Global Invasive Species Database
• Canadian Fisheries and Oceans Crayfish Plague information
• Trade Environment Database Case Study on Crayfish Plague

• Saprolegniales
• Diseases and parasites of crustaceans
• Crayfish