5 Most Common Sheep Diseases Every Producer Must Know

Disease is one of the biggest threats to profitability in sheep production. Early identification and prompt treatment can be the difference between saving an animal and losing it. This guide covers the 5 most common sheep diseases that every producer needs to know — their causes, symptoms, treatment and, most importantly, how to prevent them.

1. Enterotoxemia (Overeating Disease / Pulpy Kidney)

Enterotoxemia is one of the most common causes of sudden death in sheep, particularly in well-nourished lambs and adult sheep that experience abrupt dietary changes. It is caused by toxins produced by Clostridium perfringens types C and D in the intestine.

Causes and Risk Factors

• Sudden access to lush pasture, high-grain diets or milk overload in lambs
• Any rapid change in feed type or quantity
• Young lambs nursing from high-producing ewes
• Inadequate vaccination coverage

Symptoms

• Sudden death of apparently healthy, well-fed animals (often the best animals in the flock)
• If caught alive: convulsions, incoordination, paddling movements
• Bloat and abdominal pain
• Watery to bloody diarrhea

Treatment and Prevention

• Treatment is rarely effective once clinical signs appear — prevention is everything
• Vaccination: Vaccinate ewes 4–6 weeks before lambing with Clostridial multivalent vaccine (covers types B, C, D and tetanus). Lambs receive protection through colostrum.
• Booster lambs at 6–8 weeks and again at weaning
• Avoid abrupt dietary changes — transition animals gradually over 7–14 days

2. Footrot

Footrot is a highly contagious bacterial infection of the hoof that causes severe lameness, significant production losses and is one of the most economically damaging diseases in sheep worldwide. It is caused by the interaction between Fusobacterium necrophorum and Dichelobacter nodosus.

Symptoms

• Progressive lameness — animals kneel to graze
• Characteristic foul smell from the hoof
• Separation and undermining of the hoof horn — soft, black, necrotic tissue between the digits
• Affected animals lose weight rapidly due to inability to graze effectively

Treatment and Prevention

• Foot bathing: 10% zinc sulfate or 5% formalin solution — walk animals through 2–3 times per week
• Antibiotics: Penicillin or oxytetracycline for severe individual cases
• Trimming: Pare affected hooves to remove necrotic tissue before foot bathing
• Vaccination: Footrot vaccines reduce severity and spread — most effective as part of an eradication program
• Quarantine new animals — footrot is introduced by carrier animals
• Genetic selection: Select breeding animals with good hoof conformation and resistance to foot problems

3. Pneumonia (Respiratory Disease)

Pneumonia is a leading cause of death and production loss in sheep of all ages. It is typically caused by a combination of environmental stress and infectious agents including Mannheimia haemolytica, Pasteurella multocida, Mycoplasma species and respiratory viruses.

Risk Factors

• Overcrowding and poor ventilation
• Sudden weather changes and cold, wet conditions
• Transport stress
• Mixing animals of different ages and origins
• Poor colostrum intake in lambs (inadequate passive immunity)

Symptoms

• Fever (above 40.5°C / 105°F)
• Rapid, labored breathing — nostril flaring
• Nasal discharge (initially clear, becoming mucopurulent)
• Depression, reduced appetite, reluctance to move
• Coughing

Treatment and Prevention

• Antibiotics: Oxytetracycline, penicillin, florfenicol, enrofloxacin — early treatment is essential for survival
• Anti-inflammatories: Flunixin or meloxicam to reduce fever and lung inflammation
• Prevention: Good ventilation, avoid overcrowding, minimize stress, ensure adequate colostrum intake
• Vaccination: Pasteurella vaccines available in some countries

4. Caseous Lymphadenitis (CLA)

Caseous lymphadenitis (CLA) is a chronic bacterial disease caused by Corynebacterium pseudotuberculosis. It causes hard, cheese-like abscesses in the lymph nodes that progressively enlarge and eventually rupture, contaminating the environment with the highly persistent bacteria. It is one of the most prevalent diseases in sheep operations worldwide.

Symptoms

• Hard swellings at characteristic locations: angle of the jaw, shoulder, flank, groin (external lymph nodes)
• Swellings grow slowly over months and may eventually rupture
• Internal form: abscesses in lung, liver and spleen lymph nodes — causes progressive weight loss and poor condition with no external signs
• Chronic wasting in heavily affected animals

Management

• No reliable treatment — antibiotics do not penetrate the thick fibrous capsule of abscesses effectively
• Vaccination: Available in some countries — reduces new lesion formation but does not cure existing infections
• Culling: Remove animals with external abscesses before they rupture — prevents environmental contamination
• Biosecurity: Quarantine new animals and inspect for abscesses; avoid purchasing animals from flocks with high CLA prevalence
• Never lance or drain abscesses in the paddock — this massively contaminates the environment

5. Gastrointestinal Parasites (Worms)

Internal parasites — primarily Haemonchus contortus (barber pole worm), Trichostrongylus and Ostertagia — are arguably the single most economically important health issue in sheep production globally, especially in warm, humid climates. They cause anemia, bottle jaw, weight loss, poor wool growth and death.

Symptoms

• Pale mucous membranes (conjunctiva, gums) — the basis of the FAMACHA system
• Bottle jaw (submandibular edema) — fluid accumulation under the jaw
• Progressive weight loss and poor body condition
• Diarrhea (some species)
• Sudden death in severe infestations, especially in lambs

Treatment and Prevention

• FAMACHA scoring: Assess conjunctival color monthly and treat only animals scoring 3, 4 or 5 — reduces treatment frequency and slows resistance development
• Anthelmintics: Rotate between drug classes (benzimidazoles, levamisole, macrocyclic lactones, monepantel, derquantel) to manage resistance
• Refugia: Always leave some untreated animals to maintain susceptible worm populations
• Pasture management: Rotate pastures, avoid overgrazing, rest pastures — reduces larval contamination
• Genetic selection: Select for animals with consistently low FAMACHA scores and fecal egg counts

Recording individual health events, treatment dates, FAMACHA scores, vaccine dates and disease history for each animal in OvinApp allows you to build a complete health picture of your flock — identifying problem animals, evaluating your vaccination and parasite control protocols, and ensuring nothing falls through the cracks during busy management periods.