FieldDxBovine polioencephalomalaciaClinical signs, differential diagnosis, treatment and prevention in cattle.
Overview
A common neurologic disease of cattle. Thiamine deficiency or high dietary/ruminal sulfur intake.
Clinical signs
- Cortical blindness with no menace response but a preserved pupillary light reflex.
- Head pressing and stargazing posture.
- Dorsomedial strabismus.
- Ataxia and incoordination.
- Twitching of the ears and face.
- Anorexia and separation from the group.
- Progression to recumbency, tonic-clonic seizures and coma.
Predisposing factors
- High-concentrate, low-roughage rations.
- High sulfur intake from feed or drinking water, especially in warm weather.
- Sulfate-rich by-products of corn and beet processing; cruciferous and sulfate-accumulating weeds.
- Abrupt ration changes that disturb the rumen microbial population.
Look-alikes to rule out
Enterotoxaemia Coccidiosis Coccidiosis (Eimeria and Isospora Infestation)
Treatment
- Thiamine 10 mg/kg, first dose slow IV or IM, then every 6-8 hours IM or SC for 3-5 days.
- Dexamethasone for cerebral oedema.
- Mannitol 20% to reduce oedema.
- Diazepam or phenobarbital to control seizures.
- Supportive nursing; outcome depends on treating early.
Drugs mentioned: Phenobarbital Dexamethasone Diazepam Mannitol
Prevention
1. Supplement thiamine in feed at 3-10 mg/kg of ration. 2. Feed enough roughage to keep ruminal thiamine production going. 3. Test feed and water for sulfur and avoid high-sulfur sources. 4. Change rations gradually. 5. Hold total sulfur below 0.3% of dry matter on diets over 85% concentrate, or 0.5% on diets with at least 45% forage.
Source
MSD Veterinary Manual — Polioencephalomalacia in Ruminants (accessed 2026-07-31)
Condensed and attributed, never reproduced whole. Open the full entry in the app.