Bovine Spongiform Encephalopathy (BSE) Review

The two important transmissible spongiform encephalopathies (TSE) that you need to know about for boards are bovine spongiform encephalopathy (BSE) and scrapie in sheep. The causative agent of these diseases is still a topic of debate but a prion (abnormal protein) is theorized. The agent is extremely resistant to heat and normal sterilization procedures. This PowerPage discusses the key features of BSE in cattle and its implications for human disease.

Key Points:

  • Primary source is contaminated feed with ingredients from infected cattle
  • Key signs are hyperesthesia (Mad Cow), fine tremors, and persistent licking of the muzzle
  • Reportable disease
  • Diagnosed by characteristic histologic lesions in brain


BSE is not contagious through casual contact between cattle. The primary source is contaminated commercial feed from incorporating ingredients (i.e. Bone meal) from rendered infected cattle. Young animals are most susceptible.

Clinical Signs and Diagnosis

Onset over several months:

  • Nervousness or aggression progressing to hyperesthesia (exaggerated reflexes)
  • Incoordination, abnormal posture, difficulty rising, progressive ataxia, fine tremor
  • Weight loss, decreased milk production
  • Persistent licking of the muzzle

BSE – Requires histology of the brain for characteristic changes of bilaterally symmetric intracytoplasmic vacuolation of neurons. Can confirm with immunohistochemistry for prion protein fibrils.


There is no effective treatment. Report cases of BSE and cull animals.