Pasteurellosis in Cows: Mannheimia and Pasteurella Infections Explained
- See your vet immediately if a calf or cow has fever, rapid breathing, open-mouth breathing, marked depression, or stops eating. Pasteurellosis can worsen within hours.
- In cattle, pasteurellosis usually refers to bacterial pneumonia caused by Mannheimia haemolytica or Pasteurella multocida as part of bovine respiratory disease.
- Stressors like weaning, transport, crowding, weather swings, dust, and recent viral infection often set the stage for these bacteria to move from the upper airway into the lungs.
- Early treatment gives the best chance of recovery. Delays raise the risk of lung damage, poor growth, chronic respiratory disease, or death.
- Typical on-farm cost range is about $75-$250 per animal for exam and first-line treatment, but severe cases needing diagnostics, repeated therapy, or intensive care may reach $300-$1,500+.
What Is Pasteurellosis in Cows?
Pasteurellosis in cows usually means a bacterial respiratory infection caused by Mannheimia haemolytica and sometimes Pasteurella multocida. These bacteria are major contributors to bovine respiratory disease (BRD), especially in recently weaned, transported, commingled, or otherwise stressed calves. In many cases, they are not the first problem. A viral infection or stress event often damages the airway first, then bacteria multiply quickly and move deeper into the lungs.
Mannheimia haemolytica is especially important in fast-moving, severe pneumonia often called shipping fever. It can trigger intense lung inflammation, fever, depression, and breathing trouble. Pasteurella multocida is also linked to bronchopneumonia and may be part of mixed infections. Some cattle recover with prompt treatment, while others develop chronic poor-doers with reduced weight gain and lasting lung damage.
Although the word pasteurellosis can be used broadly, the practical concern for most cattle operations in the United States is acute bacterial pneumonia in calves and growing cattle. Because this illness can spread through a group and become serious quickly, early recognition and a herd-level plan with your vet matter as much as treatment of the individual animal.
Symptoms of Pasteurellosis in Cows
- Fever, often over 103-104.5 F
- Depression, droopy ears, or separation from the group
- Reduced appetite or not coming up to feed
- Fast breathing or increased effort to breathe
- Coughing, especially with handling or movement
- Nasal discharge that may start clear and become cloudy
- Head and neck extended while breathing
- Open-mouth breathing or obvious respiratory distress in severe cases
- Harsh lung sounds, crackles, or abnormal breathing noises
- Sudden death in peracute Mannheimia cases
Mild early cases may look like a calf that is a little quiet, warm, and off feed. More serious cases can progress to obvious pneumonia with rapid breathing, coughing, and marked lethargy. Open-mouth breathing, blue or gray gums, inability to rise, or sudden collapse are emergencies.
Call your vet promptly if more than one animal is affected, if a recently stressed calf spikes a fever, or if a treated animal is not improving within the timeframe your vet expected. In herd outbreaks, early action can reduce losses and help limit chronic lung damage in survivors.
What Causes Pasteurellosis in Cows?
The bacteria involved are often already present in the upper respiratory tract. Trouble starts when normal airway defenses are weakened. Weaning, transport, auction or sale-barn exposure, commingling with unfamiliar cattle, crowding, dust, poor ventilation, abrupt weather changes, and nutritional stress can all increase risk. Viral infections such as IBR, BRSV, PI3, or BVDV commonly make the lungs more vulnerable first.
Mannheimia haemolytica is the bacterium most often isolated from the lungs of recently weaned feedlot cattle with BRD and from calves with enzootic pneumonia. It is known for causing a strong inflammatory reaction in the lungs, which is one reason some calves become very sick very fast. Pasteurella multocida can also cause bronchopneumonia and is frequently part of mixed respiratory infections.
This is why pasteurellosis is rarely only a “bacteria problem.” It is usually a management, stress, immunity, and infection problem happening at the same time. That is also why prevention plans often include vaccination strategy, low-stress handling, ventilation improvements, and careful arrival or weaning protocols, not only antibiotics.
How Is Pasteurellosis in Cows Diagnosed?
Your vet usually starts with the history and physical exam: recent weaning or shipping, fever, appetite drop, cough, nasal discharge, and abnormal lung sounds. In many field cases, treatment begins based on these findings because waiting too long can worsen the outcome. Still, diagnosis is stronger when your vet pairs the exam with herd history and response patterns in other cattle.
When more detail is needed, your vet may recommend temperature checks, lung ultrasound, necropsy of animals that died, and laboratory testing. Samples from a deep nasopharyngeal swab, transtracheal wash, bronchoalveolar lavage, or lung tissue may be submitted for culture, PCR, and sometimes antimicrobial susceptibility testing. These tests help identify whether Mannheimia, Pasteurella, or another BRD pathogen is involved.
Diagnosis also means ruling out look-alike problems. Depending on age, housing, and outbreak pattern, your vet may consider viral BRD, Histophilus somni, Mycoplasma bovis, aspiration pneumonia, lungworms, or noninfectious respiratory disease. In herd outbreaks, postmortem findings can be especially valuable because they help guide treatment and prevention decisions for the rest of the group.
Treatment Options for Pasteurellosis in Cows
Spectrum of Care means you have options. Here are treatment tiers at different price points.
Budget-Conscious Care
- On-farm exam and temperature check
- Early treatment of mild to moderate cases based on your vet's clinical diagnosis
- A labeled first-line injectable antimicrobial selected by your vet
- Anti-inflammatory medication when appropriate
- Isolation or low-stress pen move, easy feed and water access, and close monitoring for 24-72 hours
Recommended Standard Treatment
- Full farm exam plus herd risk assessment
- Targeted antimicrobial treatment and anti-inflammatory care directed by your vet
- Follow-up recheck or retreatment plan based on response
- Basic diagnostics such as lung ultrasound, deep swab, or selected lab testing
- Group-level recommendations for metaphylaxis, vaccination timing, ventilation, stocking density, and stress reduction when indicated
Advanced / Critical Care
- Urgent veterinary assessment for severe respiratory distress or valuable animals
- Expanded diagnostics such as culture, PCR, susceptibility testing, necropsy review, or repeated imaging
- Intensive supportive care that may include IV or oral fluids, oxygen support where available, nursing care, and repeated monitoring
- Escalated treatment plan for refractory, relapsing, or mixed-pathogen disease
- Detailed herd outbreak investigation and biosecurity review
Cost estimates as of 2026-03. Actual costs vary by location, clinic, and individual case.
Questions to Ask Your Vet About Pasteurellosis in Cows
Bring these questions to your vet appointment to get the most out of your visit.
- You can ask your vet whether this looks most consistent with Mannheimia, Pasteurella, or another cause of bovine respiratory disease.
- You can ask your vet which animals need treatment right now and which ones can be monitored closely.
- You can ask your vet what signs mean a calf is getting worse, such as breathing rate, appetite, fever, or attitude changes.
- You can ask your vet whether diagnostics like culture, PCR, lung ultrasound, or necropsy would help guide treatment for this group.
- You can ask your vet how long improvement should take after treatment and when a recheck or retreatment is appropriate.
- You can ask your vet what management changes could lower risk, including ventilation, dust control, pen density, weaning strategy, and transport timing.
- You can ask your vet whether your current vaccination program matches the age, stress points, and disease risks in your herd.
- You can ask your vet which recovered animals may have chronic lung damage and how that could affect growth, breeding, or future productivity.
How to Prevent Pasteurellosis in Cows
Prevention focuses on reducing the chain of events that lets these bacteria invade the lungs. That means lowering stress, supporting immunity, and improving the air environment. Helpful steps often include low-stress weaning, minimizing commingling, avoiding overcrowding, reducing dust, improving ventilation, keeping bedding dry, and making sure calves have consistent access to water and balanced nutrition.
Vaccination may be part of the plan, but it works best when timed well and paired with management. Your vet may recommend vaccines against key viral BRD pathogens and, in some herds, bacterial respiratory components such as Mannheimia. Vaccine programs vary by region, age group, and production system. Arrival vaccination in high-risk cattle is common, but published evidence shows results can be variable, so herd-specific planning matters.
Good records are one of the most practical prevention tools. Track when cases happen, where cattle came from, temperatures, treatments used, and response rates. If deaths occur, a necropsy and lab workup can be one of the most cost-effective ways to protect the rest of the group. A prevention plan with your vet should fit your operation, not a one-size-fits-all template.