Experimental evaluation of the potential for crayfish plague transmission through the digestive system of warm-blooded predators

The crayfish plague pathogen (Aphanomyces astaci) can be transmitted through the digestive system of fish, but its dispersal through mammalian and bird digestive tracts has been considered unlikely, and direct experimental evidence remains scarce. We present a small-scale transmission experiment with European otter and American mink fed with infected crayfish, and experiments testing survival of cultures of five A. astaci strains at temperatures corresponding to those inside mammal and bird bodies. The pathogen was neither isolated from predator excrements nor transmitted to susceptible crayfish exposed to excrements. In agar-based artificial media, it occasionally survived for 15 min at 40.5 degrees C and for 45 min at 37.5 degrees C, but not so when incubated at those temperatures for 45 min and 75 min, respectively. The five tested strains differed in resistance to high temperatures, two (of genotype groups E and D) being more susceptible than other three (of groups A, B and D). Their survival to some extent varied when exposed to the same temperature after several weeks or months, suggesting that some yet-unknown factors may influence A. astaci resistance to temperature stress. Overall, we support the notion that passage through the digestive tract of warm-blooded predators makes A. astaci transmission unlikely.