Bacterial Pneumonia in Sheep: Mannheimia, Pasteurella, and Respiratory Infection
- See your vet immediately if a sheep is breathing hard, standing apart from the flock, running a fever, or has nasal discharge and a sudden drop in appetite.
- Mannheimia haemolytica and Pasteurella multocida are common bacteria involved in ovine bronchopneumonia. They often take advantage of stress, poor ventilation, transport, weaning, or a prior viral or Mycoplasma infection.
- Early treatment matters. Sheep treated promptly often do better than animals found late, down, or severely dehydrated.
- Typical 2026 U.S. cost ranges vary by setting: on-farm exam and basic treatment may run about $150-$400 per sheep, while diagnostics and repeated treatment often bring total costs to $300-$900. Intensive hospital-level care can exceed $1,000 per sheep.
What Is Bacterial Pneumonia in Sheep?
Bacterial pneumonia in sheep is a lower respiratory tract infection that inflames the lungs and airways. In many flocks, the main bacteria involved are Mannheimia haemolytica and Pasteurella multocida. These organisms can live in the upper airway of healthy sheep, then move into the lungs when normal defenses are weakened.
This condition can range from a mild cough with fever to severe bronchopneumonia, pleuritis, or sudden death. Lambs around weaning and sheep under stress are often hit hardest, but adults can also become sick, especially if another respiratory problem is already present.
For pet parents and flock managers, the biggest practical point is speed. A sheep that is dull, off feed, and breathing faster than normal may need veterinary care the same day. Early recognition gives your vet more treatment options and may improve the outlook.
Symptoms of Bacterial Pneumonia in Sheep
- Fast breathing or obvious abdominal effort
- Fever, often over 104.5°F (40.5°C)
- Depression, lagging behind, or separating from the flock
- Reduced appetite or complete feed refusal
- Coughing
- Nasal discharge or moist muzzle
- Dehydration, sunken eyes, or weakness
- Sudden death, especially in acute cases
When to worry: See your vet immediately if a sheep has labored breathing, blue or dark mucous membranes, marked weakness, froth around the mouth, or stops eating. Sheep often hide illness until they are quite sick, so a quiet animal that is easy to catch, stands alone, or breathes with effort deserves prompt attention. In flock outbreaks, even mildly affected animals should be checked early because respiratory disease can spread quickly through shared airspace and stress events.
What Causes Bacterial Pneumonia in Sheep?
Mannheimia haemolytica and Pasteurella multocida are the best-known bacterial causes of ovine bronchopneumonia. These bacteria are often considered opportunists. In other words, they may already be present in the upper respiratory tract and cause disease when the sheep's normal airway defenses are disrupted.
Common triggers include transport, weaning, crowding, poor ventilation, sudden weather shifts, commingling with unfamiliar sheep, dust, nutritional stress, and inadequate colostrum in young lambs. Primary respiratory infections can also set the stage. Merck notes that viruses such as parainfluenza-3 and adenovirus, as well as Mycoplasma ovipneumoniae, may predispose sheep to secondary infection with Mannheimia and Pasteurella.
Once the bacteria reach the lungs, inflammation can become intense. The immune response itself can add to lung damage, which is one reason some sheep decline very quickly. That is also why waiting to see if a struggling sheep improves on its own can be risky.
How Is Bacterial Pneumonia in Sheep Diagnosed?
Your vet will usually start with the basics: history, temperature, breathing pattern, hydration, lung sounds, and recent flock stressors such as transport, weaning, or weather changes. In many cases, the combination of fever, depression, increased respiratory effort, and flock history strongly suggests bacterial pneumonia.
To confirm the cause, your vet may recommend samples for bacterial culture and antimicrobial susceptibility testing. Merck lists tracheal swabs or washes, bronchoalveolar samples, and postmortem lung tissue as useful diagnostic samples. In chronic cases, culture results can be less straightforward because secondary or tertiary bacteria may be present later in the disease course.
Depending on the situation, additional testing may include necropsy of animals that died, bloodwork, or testing for underlying respiratory pathogens. A practical 2026 U.S. cost range is about $20-$90 for culture at many veterinary diagnostic labs, with $10-$30 more for susceptibility at lower-cost labs and up to about $90 for combined culture-susceptibility panels, not including farm call, sample collection, or shipping.
Treatment Options for Bacterial Pneumonia in Sheep
Spectrum of Care means you have options. Here are treatment tiers at different price points.
Budget-Conscious Care
- Prompt farm exam by your vet
- Temperature check, respiratory assessment, and hydration evaluation
- Empiric antimicrobial selected by your vet based on likely flock pathogens and legal food-animal use
- NSAID or anti-inflammatory support when appropriate
- Isolation from the flock, easy access to water, shade or shelter, and reduced handling stress
Recommended Standard Treatment
- Farm or clinic exam plus repeat recheck
- Targeted antimicrobial plan guided by flock history and, when feasible, culture and susceptibility
- Anti-inflammatory medication and supportive care
- Possible fluid therapy for dehydration
- Flock-level review of ventilation, stocking density, recent transport, and other stressors
- Necropsy and diagnostic sampling in outbreak situations if a sheep has died
Advanced / Critical Care
- Hospitalization or intensive monitored care
- IV or more intensive fluid support
- Oxygen support if available
- Serial exams and more aggressive supportive care
- Expanded diagnostics such as imaging, repeated cultures, or broader respiratory workup
- Management of complications such as pleuropneumonia, severe dehydration, or recumbency
Cost estimates as of 2026-03. Actual costs vary by location, clinic, and individual case.
Questions to Ask Your Vet About Bacterial Pneumonia in Sheep
Bring these questions to your vet appointment to get the most out of your visit.
- Does this look like an early, treatable pneumonia case or a more severe emergency?
- Which bacteria are most likely in my flock, and do you recommend culture or susceptibility testing?
- What treatment options fit this sheep's condition and my flock goals?
- How soon should I expect improvement, and what signs mean I should call back right away?
- Should this sheep be isolated, and for how long?
- Are there withdrawal times or food-safety considerations for the medications you are choosing?
- What management changes could lower the risk for the rest of the flock?
- If another sheep dies, should we submit a necropsy to guide flock treatment and prevention?
How to Prevent Bacterial Pneumonia in Sheep
Prevention starts with management. Good ventilation, lower stocking density, clean bedding, reduced dust, and careful handling around transport and weaning all help protect the airway. Lambs also need strong colostrum intake early in life, because poor passive transfer raises the risk of serious respiratory disease.
Try to reduce sudden stressors when possible. Avoid overcrowding trailers and pens, limit commingling with sheep from unrelated sources, and make feed changes gradually. Watch closely after weather swings, hauling, sale-barn exposure, or weaning, because these are common times for outbreaks to begin.
Vaccination is more complicated in the United States than in some other countries. Merck notes there are no commercially available vaccines for small-ruminant pasteurellosis in the U.S., although autogenous bacterins may sometimes be used through your vet. That means prevention often depends more on flock management, rapid treatment of early cases, and investigating underlying respiratory problems than on a routine off-the-shelf vaccine program.