When autopsies are performed, the brains of infected animals exhibit a sponge-like appearance, thus the name. The cause of the disease is not completely understood. It appears to have an incubation period of from two to eight years. There is no test to detect the presence of the disease in live cattle. There is no evidence that BSE spreads between unrelated cattle or from cattle to other species by contact.
Epidemiologic evidence suggests that maternal transmission is rare if it occurs at all.
This agent is extremely resistant to heat and to normal sterilization processes. It also does not result in a detectable immune response or inflammatory reaction in the animals carrying the disease. In an experimental study of the disease's route of development in cattle, traces of the BSE agent were found in the small intestines and retina of calves that had been fed large doses of material from BSE-infected animals. Evaluation of the presence of the BSE agent in tissues is complicated by the lack of a definitive laboratory test. Failure to identify the agent in tissues may indicate either a true absence of the agent or simply a decreased sensitivity of current diagnostic methods.