Pasteurellosis in Sheep: Respiratory Disease, Symptoms and Control
- See your vet immediately if a sheep has rapid breathing, open-mouth breathing, fever, severe depression, or suddenly stops eating.
- Pasteurellosis in sheep is usually a bacterial pneumonia linked to organisms such as Mannheimia haemolytica, Pasteurella multocida, and sometimes Bibersteinia trehalosi.
- Stress often sets the stage. Common triggers include weaning, transport, crowding, weather swings, poor ventilation, diet changes, and mixing groups.
- Early treatment matters. Sheep treated in the first stage of illness usually do better than animals treated after they are down, dehydrated, or severely short of breath.
- Typical US cost range for exam, antibiotics, and basic flock-level care is about $150-$500 for one mildly affected sheep, while intensive treatment or multiple sick animals can raise costs to $500-$1,500+.
What Is Pasteurellosis in Sheep?
Pasteurellosis in sheep is a bacterial disease that most often shows up as bronchopneumonia, a serious infection in the lungs and airways. The organisms most commonly involved are Mannheimia haemolytica and Pasteurella multocida, with Bibersteinia trehalosi also playing a role in some lambs. These bacteria can live in the upper respiratory tract of healthy sheep, then take advantage when the animal is stressed or its normal airway defenses are weakened.
In practical terms, this means a sheep may look normal one day and then develop fever, nasal discharge, coughing, fast breathing, and marked depression soon after a stressful event. Young lambs around weaning can be hit especially hard, but sheep of any age can be affected. Some cases are mild at first. Others move quickly and can lead to sudden death.
For pet parents and flock caretakers, the big takeaway is that pasteurellosis is not always a "random" pneumonia. It is often part of a larger respiratory problem involving stress, environment, and sometimes viral or mycoplasma infections. Fast recognition and a prompt plan with your vet can improve the outlook and help protect the rest of the flock.
Symptoms of Pasteurellosis in Sheep
- Fever, often with a sudden drop in appetite
- Depression, isolation from the flock, or reluctance to move
- Fast breathing or increased effort to breathe
- Coughing, especially after handling or exercise
- Nasal discharge that may start clear and become cloudy
- Head and neck extended while breathing
- Open-mouth breathing or severe respiratory distress
- Weakness, dehydration, or lying down more than normal
- Poor growth or unthriftiness in lambs with longer-lasting cases
- Sudden death in severe or peracute infections
Mild cases may begin with reduced feed intake, a fever, and subtle breathing changes. More serious cases can progress to obvious respiratory distress, marked lethargy, and collapse. Lambs may decline faster than adults.
See your vet immediately if any sheep is breathing hard, breathing with its mouth open, cannot keep up with the flock, or dies suddenly after recent stress such as weaning, transport, crowding, or a weather change. Those signs can point to severe pneumonia and a flock-level problem that needs quick attention.
What Causes Pasteurellosis in Sheep?
Pasteurellosis usually develops when bacteria that are already present in the nose or throat move deeper into the lungs. The main bacterial players are Mannheimia haemolytica, Pasteurella multocida, and sometimes Bibersteinia trehalosi. On their own, these organisms may not cause disease in a healthy sheep. Trouble starts when normal lung defenses are disrupted.
Common triggers include weaning, transportation, commingling with unfamiliar sheep, sudden diet changes, crowding, poor ventilation, heat or cold stress, and exposure to rain or harsh weather. In many flocks, a viral infection or Mycoplasma ovipneumoniae may weaken the respiratory tract first, making it easier for these bacteria to invade lung tissue.
Lambs with inadequate colostrum intake or waning maternal immunity can be more vulnerable. Overstocking, dusty bedding, ammonia buildup, and delayed treatment also increase risk. Because several factors often overlap, your vet may look beyond the sick sheep and assess housing, handling, nutrition, and recent flock events.
How Is Pasteurellosis in Sheep Diagnosed?
Your vet usually starts with the basics: history, recent stressors, temperature, breathing rate, lung sounds, and how many sheep are affected. In many cases, the pattern is very suggestive: a sheep or group of sheep becomes ill after weaning, transport, weather stress, or crowding, with fever and signs of pneumonia.
Diagnosis may be based on clinical signs alone in a straightforward field case, especially when treatment needs to begin right away. For a stronger diagnosis, your vet may recommend nasal or deep respiratory samples for bacterial culture, and in some cases testing for other respiratory pathogens that may be involved. Culture can help identify the organism and guide antibiotic choices, although treatment often starts before results return.
If a sheep dies or the outbreak is severe, a necropsy can be one of the most useful flock-level tools. Lung lesions, distribution of pneumonia, and lab testing of tissues can help confirm pasteurellosis and rule out other causes of sudden respiratory loss. This can be especially important when several sheep are affected or when treatment response has been poor.
Treatment Options for Pasteurellosis in Sheep
Spectrum of Care means you have options. Here are treatment tiers at different price points.
Budget-Conscious Care
- Farm call or basic exam for one sheep
- Early injectable antibiotic selected by your vet
- Anti-inflammatory medication if appropriate
- Isolation from the flock and reduced handling stress
- Warm, dry shelter with easy access to water and palatable feed
- Basic monitoring of temperature, appetite, and breathing effort
Recommended Standard Treatment
- Full veterinary exam and treatment plan
- Appropriate antimicrobial therapy started promptly
- Anti-inflammatory or fever control as directed by your vet
- Supportive care for dehydration and poor intake
- Targeted diagnostics such as culture or selected lab testing
- Review of ventilation, stocking density, recent stressors, and flock management
Advanced / Critical Care
- Urgent veterinary assessment for severe respiratory distress
- Repeated treatments, intensive supportive care, and close rechecks
- IV or more aggressive fluid support when feasible
- Expanded diagnostics such as culture, susceptibility testing, and necropsy of losses
- Flock outbreak investigation and prevention planning
- Referral-level care where available for valuable breeding stock or severe cases
Cost estimates as of 2026-03. Actual costs vary by location, clinic, and individual case.
Questions to Ask Your Vet About Pasteurellosis in Sheep
Bring these questions to your vet appointment to get the most out of your visit.
- Does this look like pasteurellosis, or are other causes of pneumonia also likely in my flock?
- Which sheep need treatment right now, and which ones should be watched more closely?
- What early warning signs mean a sheep needs urgent recheck or emergency care?
- Should we culture a sample or submit a necropsy to confirm the cause and guide treatment?
- Are ventilation, crowding, bedding dust, or weather exposure contributing to this outbreak?
- Do you suspect a viral problem or Mycoplasma infection setting up these bacterial pneumonias?
- What isolation and handling steps should we use to reduce spread and stress in the flock?
- What prevention plan makes sense for our farm during weaning, transport, and other high-risk times?
How to Prevent Pasteurellosis in Sheep
Prevention focuses on stress reduction and respiratory management. Good ventilation, dry bedding, clean water, and avoiding overcrowding all matter. Try to reduce abrupt changes in feed, grouping, and handling. Weaning, transport, and mixing animals from different sources are common high-risk periods, so these events should be planned carefully.
Work with your vet to review flock flow, lambing and weaning practices, colostrum management, and housing conditions. Lambs that receive good early care and are not pushed through multiple stressors at once are often more resilient. If pneumonia has been recurring, your vet may recommend a deeper review of ventilation, stocking density, and whether other respiratory pathogens are circulating.
In the United States, prevention relies heavily on management and husbandry, because commercially available vaccines specifically for small-ruminant pasteurellosis are limited or unavailable. That makes early detection even more important. Pulling sick sheep promptly, treating early, and investigating deaths can help reduce losses in the rest of the flock.