Prions of chronic wasting disease are spread in feces & persist for long periods in soil

[steven johnson]

Creutzfeldt-Jakob, mad cow and chronic wasting disease are all the prion diseases. Each of these diseases is caused by a different strain of prions and can lead to dementia and death in humans. Prions from deer and elk tended to bind to clay in soil and can persist indefinitely. The theory is that the agent is retained in the soil where it is eaten along with plants and infects other animals. Apparently, bovine prions are not shed in the feces and do not present this mode of transmission.

In the UK 4.4 million cattle were slaughtered during the mad cow outbreak when humans became infected and 164 died, presumably through consuming some of the nervous tissue of infected cattle.

Researchers are reporting that they have solved a longstanding mystery about the rapid spread of a fatal brain infection in deer, elk and moose in the Midwest and West.

The infectious agent (a prion), which leads to chronic wasting disease, is spread in the feces of infected animals long before they become ill, according to a study published online Wednesday by the journal Nature. The agent is retained in the soil, where it, along with plants, is eaten by other animals, which then become infected.

Unlike other animals, Dr. Prusiner said, deer give off the infectious agent, a form of protein called a prion, from lymph tissue in their intestinal linings up to a year before they develop the disease. By contrast, cattle that develop a related disease, mad cow, do not easily shed prions into the environment but accumulate them in their brains and spinal tissues.

In captive herds (of deer), up to 90 percent of animals develop the disease, Dr. Prusiner said. In wild herds, a third of animals can be infected.

Study Spells Out Spread of Brain Illness in Animals