Aphanomyces astaci

General/Background information: Aphanomyces astaci is a water mold/fungus that infects crayfish, most notably European species. Though all species of crayfish can be affected by this mold/fungus to one degree or another (some North American species have built up an immunity to it, but can still be carrying/spreading the spores to others). This mold/fungus is originally from North America and has been spread through-out Europe causing immense amounts of damage to natural species for the last century. The origins of the spread of this mold/fungus are continually under debate, and the most commons theories can be found here (http://www.american.edu/ted/crayfish.htm).


Signs of the disease: Crayfish suddenly become more visible during the day (crayfish are normally nocturnal) or in the light and act very dazed and confused. The crayfish may exhibit coordination issues, such as being unable to right themselves if they are on their backs or the inability to perform their "tail flick" maneuver. Some crayfish will exhibit sudden coloration changes, as well. But more often than not, signs of this disease are not present and the mold/fungus' presence becomes known when the crayfish suddenly dies (in aquariums) or they die in mass numbers (wild populations). For a definitive diagnosis, a professional examination (autopsy) must be performed.

Prophylactic treatment: A dosage of 5g/l of MgCl2.6H2O (Magnesium Chloride hexahydrate) may be added to the aquarium water.

Treatment: Isolation from any tank-mates to prevent the spread of the disease. And treatment with antibacterial and/or antifungal tropical fish medications.

Cure: There is no known cure for this disease (currently).

Sources:
american.edu/ted/crayfish.htm
bluecrayfish.com
crayfishmates.com