Pleuritis and Pleuropneumonia in Sheep: Chest Infection Warning Signs

Pleuritis means inflammation of the pleura, the thin lining around the lungs and inside the chest wall. Pleuropneumonia means the infection involves both the lungs and that lining. In sheep, this often develops as a severe bacterial respiratory disease that can cause pain, fever, breathing difficulty, and rapid decline.

These cases are more than a routine cough. When infection spreads into the chest, sheep may breathe with abdominal effort, move less, and separate from the flock. In some animals, especially lambs or stressed sheep, the first sign may be sudden death.

A common pattern is that bacteria already living in the upper airway take advantage of stress or another respiratory insult. Merck Veterinary Manual notes that Mannheimia haemolytica and Pasteurella multocida are frequent causes of bacterial pneumonia in sheep and goats, and that viral infections or Mycoplasma ovipneumoniae can set the stage for more severe disease. Because pleural involvement can mean fibrin, fluid, and lung damage inside the chest, prompt veterinary care matters.

In sheep, pleuritis and pleuropneumonia are usually caused by bacterial infection. Important bacteria include Mannheimia haemolytica, Pasteurella multocida, and sometimes Bibersteinia trehalosi. These organisms may live in the upper respiratory tract without causing disease until the sheep is stressed or the normal airway defenses are weakened.

Common triggers include transport, weaning, sudden diet change, crowding, mixing animals from different sources, poor ventilation, and severe weather. Merck Veterinary Manual also notes that respiratory viruses and Mycoplasma ovipneumoniae can predispose sheep to secondary bacterial pneumonia. In practical terms, that means a sheep may start with a milder respiratory problem and then develop a much more serious chest infection.

Less commonly, pleuritis can follow aspiration, penetrating chest trauma, or spread from nearby infection. Your vet will also think about other causes of breathing trouble in sheep, including lungworms, laryngeal disease, ovine pulmonary adenocarcinoma, and toxic or environmental problems. The exact cause matters because treatment plans, flock risk, and prognosis can differ.

Your vet usually starts with history and a hands-on exam. Important clues include recent transport, weaning, weather stress, new additions to the flock, fever, dehydration, abnormal breathing effort, and reduced rumen activity. Lung sounds can be misleading in some severe cases, especially if pleural fluid is present, so a normal-sounding chest does not rule out serious disease.

Diagnosis often combines the exam with practical farm diagnostics. Your vet may recommend rectal temperature, bloodwork, and thoracic ultrasound to look for pleural fluid, fibrin, lung consolidation, or abscess-like changes near the chest wall. Ultrasound is especially helpful when pleuritis is suspected because it can show fluid and fibrin that are not obvious from auscultation alone.

In some cases, your vet may collect samples such as nasal swabs, transtracheal or airway samples, pleural fluid, or tissues from a recently deceased sheep for culture and sensitivity testing. Necropsy can be very valuable in flock outbreaks because it may confirm fibrinous pleuropneumonia and help guide treatment and prevention decisions for the rest of the group.

Prevention focuses on lowering respiratory stress and reducing the chance that normal airway bacteria turn into a serious chest infection. Good ventilation, clean dry bedding, avoiding overcrowding, and minimizing abrupt changes in diet or environment all help. Lambs also benefit from strong colostrum intake and steady nutrition, because weaker immunity raises pneumonia risk.

Management around stressful events matters. Weaning, transport, commingling, and severe weather are common times for outbreaks. Plan these periods carefully, avoid mixing age groups or source groups when possible, and watch closely for early respiratory signs afterward. If your flock has repeated problems, your vet may recommend a prevention plan that includes timing changes, biosecurity steps, and in some situations vaccination or strategic metaphylaxis.

Because respiratory disease in sheep is often a flock issue rather than a one-animal issue, a necropsy on a fresh death can be one of the most useful prevention tools. It can help confirm the organisms involved and guide practical changes for the rest of the group. Work with your vet to build a flock-specific plan that matches your housing, climate, lambing schedule, and budget.