A cow shows rigid ears, wide eyes, and lips drawn back. Which disease is suspected?

A cow shows rigid ears, wide eyes, and lips drawn back. Which disease is suspected?

• A. Rabies
• B. Tetanus
• C. Botulism
• D. Bovine respiratory disease

Answer: (B)

The described signs point to a toxin-mediated, sustained muscle contraction pattern. Tetanus occurs after infection with Clostridium tetani, which releases tetanospasmin. This toxin blocks inhibitory signals in the spinal cord and brainstem, so neurons fire continuously. That produces rigid, painful muscle contractions, including facial muscles. In cattle this can manifest as a fixed facial expression with a drawn-back lip and stiff ears—often described as a “sardonic grin” or risus sardonicus. The other conditions don’t fit these signs. Rabies usually presents with behavioral changes, aggression or weakness and later neurologic signs, not a locked facial expression with ear rigidity. Botulism causes flaccid paralysis and weakness rather than rigid, spastic contractions. Bovine respiratory disease shows coughing, nasal discharge, fever, and breathing difficulty, not facial muscle rigidity. So, the best match for rigid ears, wide eyes, and lips drawn back is tetanus.

The described signs point to a toxin-mediated, sustained muscle contraction pattern. Tetanus occurs after infection with Clostridium tetani, which releases tetanospasmin. This toxin blocks inhibitory signals in the spinal cord and brainstem, so neurons fire continuously. That produces rigid, painful muscle contractions, including facial muscles. In cattle this can manifest as a fixed facial expression with a drawn-back lip and stiff ears—often described as a “sardonic grin” or risus sardonicus.

The other conditions don’t fit these signs. Rabies usually presents with behavioral changes, aggression or weakness and later neurologic signs, not a locked facial expression with ear rigidity. Botulism causes flaccid paralysis and weakness rather than rigid, spastic contractions. Bovine respiratory disease shows coughing, nasal discharge, fever, and breathing difficulty, not facial muscle rigidity.

So, the best match for rigid ears, wide eyes, and lips drawn back is tetanus.