Licensed from Columbia University Press
Licensed from Columbia University Press
Licensed from Columbia University Press
Licensed from Columbia University Press
Extinct aquatic mammal (Hydrodamalis gigas) that lived around islands in the Bering Sea. It was discovered in 1741 and described by a member of Vitus Bering's expedition. At least 24 ft (7.5 m) long, it had no teeth, a small head, and a broad, horizontal, forked tail fluke; its dark brown skin was sometimes streaked or spotted with white. It browsed on seaweed. Russian sealers hunted it for food and fur; by 1768 the entire population, estimated at about 5,000, had been exterminated. The term also refers to dugongs and manatees.
Learn more about sea cow with a free trial on Britannica.com.
Fatal neurodegenerative disease of cattle. Symptoms include behavioral changes (e.g., agitation), gradual loss of coordination and locomotive function, and, in advanced stages, weight loss, fine muscular contractions, and abnormal gait. Brain tissue becomes pitted with holes and spongy. Death usually follows within a year. The disease is similar to the neurodegenerative disease of sheep called scrapie. No treatment is known. A BSE epidemic in Britain that began in the mid-1980s is believed to have been caused by the use of cattle feed containing supplements made from ruminant carcasses and trimmings. Hundreds of thousands of infected cattle were slaughtered and the use of animal-derived protein supplements ended. The cause of both BSE and scrapie is attributed to an infectious aberrant protein called a prion. The unusual occurrence of Creutzfeldt-Jakob disease, another prion-related illness, in young people beginning in the mid-1990s may be linked to eating meat from cattle with BSE.
Learn more about mad cow disease with a free trial on Britannica.com.
|
|
|
|
|
|
|
|
|
|
Copyright © 2009, Dictionary.com, LLC. All rights reserved.
