 They may also fall ill from listeriosis and spirochetosis, as well as acting as vectors in spreading erysipelas, brucellosis and tick-borne encephalitis.A mysterious fatal disease near Lake Sartlan in the Novosibirsk Oblast was noted among local red foxes, but the cause was undetermined.The possibility was considered that it was caused by an acute form of encephalomyelitis, which was first observed in captive-bred silver foxes.