Clostridial Disease in Sheep: Deep Welfare Guide
Overview of Clostridial Diseases
Several clostridial diseases affect sheep, caused by different Clostridium species: pulpy kidney (Cl. perfringens type D), lamb dysentery (Cl. perfringens type B), struck (Cl. perfringens type C), tetanus (Cl. tetani), braxy (Cl. septicum), black disease (Cl. novyi), blackleg (Cl. chauvoei), and botulism (Cl. botulinum). Each causes acute, often rapidly fatal disease. Most are associated with specific triggers: overfeeding (pulpy kidney), soil contamination of wounds (tetanus, blackleg), liver fluke damage (black disease).
Welfare Consequences
Clostridial diseases typically cause sudden death, but affected animals that survive briefly experience convulsions, colic, recumbency, and profound pain and distress before death. Tetanus causes progressive muscle spasms, opisthotonos (arched back), lockjaw, and a prolonged agonising death. The intensity and duration of suffering, even when brief, makes prevention the paramount welfare priority.
Vaccination Programmes
Combined clostridial vaccines (multivalent vaccines covering 7 or 8 organisms, e.g., Heptavac P Plus, Covexin 8) provide broad protection. Ewes should receive primary vaccination (two doses 4-6 weeks apart) followed by annual pre-lambing boosters to pass immunity via colostrum to lambs. Lambs from unvaccinated ewes should receive primary vaccination from 10-12 weeks. Lambs from vaccinated ewes need their own vaccine course to maintain protection past the age of maternal antibody waning (typically 3-4 months).
Husbandry Risk Factors
Risk is increased by: sudden dietary changes (particularly onto lush grass, causing pulpy kidney); poor colostrum intake in lambs; liver fluke infestation (predisposing to black disease); deep puncture wounds or castration/docking without antiseptic care (tetanus risk); high-stocking environments with soil contamination. Risk management involves vaccination, avoiding abrupt dietary changes, and good hygiene at surgical procedures.
Farm-Level Welfare Implementation
Maintaining complete vaccination records for all sheep allows identification of animals at risk. Bringing new stock onto the farm should include vaccination check and booster if uncertain. Investigating sudden deaths (post-mortem, laboratory confirmation) establishes which clostridial disease is present and guides targeted prevention. Farmers and vets should review vaccination schedules annually, adjusting based on farm-specific clostridial disease history.