Lameness and musculoskeletal disorders in sheep

Primary Causes:
- Injuries: Limb fractures are very common in young lambs, often caused inadvertently by adults.
- Specific Foot Infections: Includes contagious footrot and interdigital dermatitis.
Systemic Disease Origins: Can be caused by septic arthritis, tetanus, white muscle disease, frostbite, selenium toxicosis, and laminitis.
Diagnostic Mimicry: Weakness or neurologic signs from diseases like scrapie or listeriosis can be misinterpreted as lameness.
Stabilization: Fractures in lambs are typically treated with splints or casts for 3–6 weeks.

Etiology: The primary agent is Dichelobacter nodosus (an obligate pathogen); Fusobacterium necrophorum plays a synergistic role by colonizing moist interdigital skin.
Classification:
- Benign: Confined to interdigital skin with minimal underrunning.
- Virulent: A chronic, necrotizing disease that destroys the hoof matrix, leading to detachment of the hoof wall.
Clinical Findings: Severe lameness, characteristic foul necrotic odor, and distorted, gnarled hooves.
Management & Eradication:
- Treatment: Long-acting parenteral oxytetracycline or macrolides; 10% zinc sulfate footbaths.
- Three-Phase Eradication (Australia): Control (during active spread), Eradication (dry season; culling non-responders), and Surveillance (immediate exam of any new lameness).
Prevention: Strict biosecurity, quarantine of new animals for several weeks, and vaccination where available.

Etiology: Caused by Trueperella pyogenes and F. necrophorum; often precedes a footrot outbreak.
Clinical Presentation: Red, hairless, moist, and swollen interdigital skin; may affect up to 90% of a flock.
Risk Factors: Primarily driven by wet weather and damp pastures.
Treatment: External application of 10% zinc sulfate via footbath or aerosol.

Characteristics: A mass of fibrous tissue between the toes that spreads them apart.
Clinical Impact: Growth of "tendrils" upward between phalanges causes severe lameness.
Management: Early surgical removal (cryosurgery/electrocautery) is possible, but the condition tends to recur if tendrils cannot be fully removed.

Anatomy: A sebaceous gland located in a pouch between the phalanges.
Clinical Presentation: Distention of the pouch or local cellulitis/abscess; rarely causes lameness.
Treatment: Manual expression of contents and local or systemic antimicrobials.