What are Transmissible Spongiform Encephalopathies (TSEs)?

Transmissible Spongiform Encephalopathies (TSEs) are neurological diseases which are characterized by degeneration of the brain tissue, causing a number of plaques and small holes to form. When the brain is examined during an autopsy, it looks a bit like a sponge, which explains the term “spongiform.” The cause for TSEs is generally believed to be an abnormal protein called a prion, and currently these diseases have no cure.

Prions are proteins which contain no genetic material, instead using unique folding behaviors to replicate themselves, infecting healthy proteins along the way. Prions can survive extreme temperature changes and a variety of antiseptics, making it very difficult to eradicate them. Prion diseases are a concern in many communities because the diagnosis is often missed, since the symptoms can resemble other conditions, like senile dementia. Generally, humans are only diagnosed with TSE when they exhibit traits associated with a rare genetic version, or when they experience dementia at an unusually young age, and a firm diagnosis can only be obtained at autopsy, as it requires an inspection of the brain tissue.

The symptoms of TSEs typically start with subtle personality changes, and become progressively worse as the function of the nervous system is disrupted. Patients may have difficulty walking or speaking, and they often experience violent dementia as the infection literally bores holes into their brains. After a certain point, the nervous system simply fails, causing the patient to lapse into a coma and eventually die.

TSEs can be found in a number of animals. In humans, the most well known example is probably Creutzfeldt-Jakob disease, but other human TSEs include Gerstmann-Straussler-Scheinker disease, kuru, and Fatal Familial Insomnia. Sheep and goats can get scrapie, while cows get Bovine Spongiform Encephalitis (BSE), also known as mad cow. TSEs have also been diagnosed in deer and elk (chronic wasting disease), cats (feline spongiform encephalitis), and mink (transmissible mink encephalopathy).

In all cases, animals appear to contract TSE by ingesting infected neurological tissue. In animals, the most common cause is contaminated feed, as the practice of including rendered animal parts in animal feed for additional protein is quite common. TSE can also be contracted from brain surgery, although this is rare, as the prions responsible for TSE are able to survive the autoclave.

Because these diseases cannot be cured, most treatment is focused on keeping the patient comfortable. When TSE is suspected, patients may be offered muscle relaxants to help them cope with the twitching and other physical symptoms associated with late-stage TSE, as the body starts to lose control. These drugs can also keep patients with extreme dementia more relaxed, making them easier to care for.