This photo shows the slimming effects of chronic wasting disease. Photo courtesy of the Colorado Division of Wildlife
Chronic wasting disease (CWD) is a TSE that affects some types of deer, elk and moose and is always fatal. CWD's major symptom is uncontrollable progressive weight loss, but most cases also involves behavioral changes that are similar to those of TSE in humans, including blank expressions, bizarre repetitive behavior, drastic anti-social behavior, and skittishness. Interestingly, the animals tend to lose interest in hay, but not other foods, and drink more liquids (and thus urinate more). CWD was discovered and first diagnosed in the mid 1980s.
A TSE affecting members of the cat family was reported in the U.K. in the 1990s. Feline spongiform encephalopathy has a long incubation period and may have been transmitted through BSE infected beef or pet food products. FSE is characterized by unusual behavior, such as aggression or timidity distinct from the cat's usual character, abnormal gait, poor motor control or judgment and tremors.
In "mad cow," the bovine spongiform encephalopathy agent is most likely transmitted among commercial cattle through feed. Cattle are naturally herbivores; they eat primarily grass. Industrial cattle farmers make their cows cannibals, mixing cow parts into feed for extra protein. "Meat and bone meal" is a multi-purpose 50% protein powder rendered from the fat, bones, intestines, and other unwanted parts of farmed animals, including whole cattle (who died before slaughter of often unknown causes) and nervous tissue. It is no longer legal to add "meat and bone meal" to cattle feed, though it is still used as filler in pet food, as a fertilizer and as an alternative fuel source. Meat and bone meal has been available at an increased volume since the mad cow crisis meant lots of slaughtered cattle unfit for human consumption. Supplementing cattle feed with proteins from animal byproducts is less common in the United States, as we typically use soybeans, which grow cheaply and plentifully in the U.S. and not in the U.K.
Scrapie is a TSE (and therefore also a fatal neurodegenerative disease) that affects sheep and goats. Some breeds are more susceptible than others, and there have been no incidents of scrapie in Australia and New Zealand to date. Scrapie is relatively easy to test for and the more susceptible allele is being bred out of commercial animals. Scrapie is so called because infected sheep and goats experience an itching and pathological will to scrape their hides or fur off against sharp or rough surfaces. Other symptoms include abnormal gait, collapsing and compulsive lip smacking. There have been no reports of scrapie being transmitted to humans.