FieldDxSepticemia and Thrombotic Meningoencephalitis in Sheep Associated With Histophilus somniClinical signs, differential diagnosis, treatment and prevention in sheep.
Overview
A systemic bacterial disease that can spread from the bloodstream to the brain, heart and joints. Histophilus somni.
Clinical signs
- Sudden death may be the first thing seen.
- Profound lethargy.
- Fever and rapid breathing.
- Stiffness, muscle weakness, ataxia and lameness.
- Extreme dyspnoea in the pleuritic form.
- Recumbency and hyperaesthesia in the encephalitic form.
- Blindness where the CNS is involved.
Predisposing factors
- Recently weaned young stock held in confinement.
- High-stress transition and transport.
- Concurrent respiratory viral infection.
- Poor response to immunisation under stress.
Treatment
- Florfenicol 20 mg/kg IM, repeated after 48 hours, or 40 mg/kg SC once.
- Antimicrobials work best given early.
Drugs mentioned: Florfenicol
Prevention
1. Bacterins containing H. somni, given as two doses. 2. Efficacy varies because of biofilm formation and timing.
Source
MSD Veterinary Manual — Histophilosis (accessed 2026-07-31)
A Textbook of the Diseases of Cattle, Horses, Sheep, Pigs and Goat by ELSEVIER — Septicemia And Thrombotic Meningoencephalitis In Sheep Associated With Histophilus Somni
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