Because of growing concern about BSE, USDA epidemiologists are carefully monitoring all new scientific data about TXE's from around the world. The epidemiologic data suggests that BSE in England may have been caused by feeding cattle rendered protein produced from the carcasses of scrapie-infected sheep. An alternate theory is that BSE had existed in undetectable levels in the British cattle population prior to 1986. The practice of using products such as meat and bonemeal in cattle rations as a source of protein has been common for several decades. There is no evidence that BSE spreads from unrelated cattle to 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 evoke a detectable immune response or inflammatory reaction in host animals. In an experimental study of the disease's biological route of development in cattle, traces of the BSE agent were detected 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.