Mycoplasma bovis in Cows: Pneumonia, Mastitis, Arthritis, and Control
- See your vet immediately if a cow has labored breathing, a sudden drop in milk, swollen painful joints, or multiple quarters with abnormal milk.
- Mycoplasma bovis is a contagious bacterial pathogen of cattle that commonly causes chronic pneumonia, mastitis, arthritis, and sometimes ear infections, especially in calves and dairy herds.
- Cases often do not respond as expected to routine antibiotics, so herd-level testing, isolation, and biosecurity matter as much as individual treatment.
- Diagnosis usually requires targeted testing such as mycoplasma milk culture, PCR, or samples from the respiratory tract or joints because routine culture can miss it.
- Realistic 2025-2026 U.S. veterinary cost range is about $80-$250 per sick animal for an exam and basic testing, $25-$80 per milk culture or PCR sample, and several hundred to several thousand dollars more for herd investigation, treatment, segregation, or losses from culling and reduced production.
What Is Mycoplasma bovis in Cows?
Mycoplasma bovis is a contagious bacterial pathogen of cattle. It is well known for causing chronic pneumonia, mastitis, and arthritis, and it can also be linked with ear infections in calves. In dairy herds, it is one of the most important mycoplasma species because it can spread in respiratory secretions and during milking when infected milk contaminates equipment or contacts other cows.
Unlike many bacteria, mycoplasmas do not have a normal cell wall. That matters because some common antibiotics target the cell wall and may not work well against this organism. In real life, that means cows may stay sick longer, relapse, or show poor response to treatment plans that would help with other causes of pneumonia or mastitis.
Mycoplasma bovis can affect individual animals, but it is often a herd problem. A calf may start with respiratory disease and later develop swollen joints. A dairy cow may have mastitis in more than one quarter, abnormal milk, and a sharp drop in production. Because the disease can move through groups of cattle, early recognition and a plan with your vet are important for both animal welfare and herd control.
Symptoms of Mycoplasma bovis in Cows
- Chronic cough or pneumonia that does not improve as expected
- Fever, depression, nasal discharge, and increased breathing effort
- Lameness with hot, swollen, painful joints
- Mastitis in multiple quarters with abnormal, watery, flaky, or discolored milk
- Sudden drop in milk production with little improvement after treatment
- Calves with ear droop, head tilt, or signs of ear infection
- Weight loss, poor growth, or poor feed efficiency after respiratory illness
- Some cows with severe mastitis may look fairly normal otherwise
Worry sooner, not later, if you see breathing trouble, multiple lame calves, several mastitis cases at once, or mastitis that is not responding as expected. Mycoplasma bovis often becomes obvious when more than one animal is affected or when signs keep returning.
See your vet immediately for severe breathing effort, inability to rise, dehydration, a painful swollen joint, or a sudden cluster of mastitis cases in the herd. Those patterns can point to a contagious problem that needs both individual care and herd-level control.
What Causes Mycoplasma bovis in Cows?
Mycoplasma bovis infection is caused by exposure to the M. bovis bacterium. It spreads mainly through respiratory secretions, close contact between cattle, and in dairy settings through infected milk and milking equipment. Calves can also be exposed when fed contaminated milk from infected cows.
Outbreaks are more likely when cattle are moved, mixed, transported, stressed, or introduced from outside sources without a quarantine period. Young calves, recently weaned calves, feedlot cattle, and fresh dairy cows can be especially vulnerable because stress and crowding make respiratory spread easier.
This disease is often part of a bigger picture. In respiratory disease, Mycoplasma bovis may act along with viruses and other bacteria in the bovine respiratory disease complex. In mastitis, it behaves like a contagious udder pathogen, so one infected cow can become a source for others during milking. That is why your vet may focus not only on the sick cow, but also on milking order, hospital pens, calf feeding practices, and new-animal biosecurity.
How Is Mycoplasma bovis in Cows Diagnosed?
Diagnosis starts with the pattern of disease. Your vet may suspect Mycoplasma bovis when there is chronic pneumonia, arthritis after respiratory disease, mastitis in multiple quarters, poor response to treatment, or several related cases in a group. History matters a lot, especially recent cattle purchases, fresh-cow problems, or calves with pneumonia and ear infections.
Testing usually needs to be targeted. For mastitis, your vet may submit bulk tank milk, composite milk, or quarter milk samples for mycoplasma culture or PCR. For respiratory disease, samples may include deep nasal or respiratory samples, lung tissue, or necropsy specimens. Joint fluid or tissues may be tested in arthritic cases. Routine bacterial culture can miss mycoplasma unless the lab is specifically asked to look for it.
Because this can be a herd issue, diagnosis often includes more than one animal. Your vet may recommend screening fresh cows, cows with clinical mastitis, high-SCC cows, hospital-pen animals, or calves with chronic respiratory disease. That broader approach helps identify whether the problem is isolated or moving through the herd.
Treatment Options for Mycoplasma bovis in Cows
Spectrum of Care means you have options. Here are treatment tiers at different price points.
Budget-Conscious Care
- Veterinary exam and triage of the sickest animals
- Targeted testing of the highest-risk cases rather than whole-herd screening
- Supportive care such as fluids, anti-inflammatory medication, nursing care, and easier access to feed and water as directed by your vet
- Isolation or segregation of suspect animals
- Milking infected or suspect cows last, or keeping them out of the tank if your vet advises it
- Focused culling decisions for chronic mastitis or nonresponsive cases
Recommended Standard Treatment
- Veterinary-guided treatment plan for pneumonia, arthritis, or mastitis based on clinical signs, welfare, and likely response
- Targeted diagnostics such as mycoplasma culture or PCR on milk, respiratory, or joint samples
- Herd investigation including bulk tank testing and screening of fresh cows, clinical mastitis cows, high-SCC cows, or hospital groups
- Segregation protocols, milking-order changes, and calf-feeding review
- Biosecurity plan for new additions, sick pens, shared equipment, and employee workflow
- Culling recommendations for chronic mastitis cows or animals with poor long-term outlook
Advanced / Critical Care
- Repeated veterinary visits and advanced diagnostics, including necropsy or expanded laboratory testing when needed
- Aggressive supportive care for valuable or severely affected animals under close veterinary supervision
- Comprehensive herd outbreak investigation with repeated bulk tank surveillance and broader individual-animal testing
- Detailed milking-system, calf program, and traffic-flow review to identify transmission points
- Intensive segregation, dedicated equipment, and stricter quarantine protocols for purchased or returning cattle
- Strategic culling and long-term herd monitoring plan
Cost estimates as of 2026-03. Actual costs vary by location, clinic, and individual case.
Questions to Ask Your Vet About Mycoplasma bovis in Cows
Bring these questions to your vet appointment to get the most out of your visit.
- Based on this cow’s signs, how likely is Mycoplasma bovis compared with other causes of pneumonia, mastitis, or lameness?
- Which samples should we collect right now: milk, respiratory samples, joint fluid, or necropsy samples?
- Does the lab need special instructions to culture or PCR for mycoplasma?
- Should this cow be isolated, milked last, or removed from the tank while we wait for results?
- Do you recommend testing the bulk tank, fresh cows, hospital-pen cows, or calves with respiratory disease?
- What is the realistic outlook for recovery, future milk production, and recurrence in this animal?
- At what point does culling become the most practical option for welfare and herd control?
- What quarantine and biosecurity steps should we use for new cattle, shared equipment, and calf feeding?
How to Prevent Mycoplasma bovis in Cows
Prevention focuses on biosecurity, early detection, and limiting spread within the herd. Work with your vet to quarantine new, borrowed, or returning cattle before they join the main group. A 30-day isolation period is a common starting point in U.S. biosecurity guidance, with monitoring for illness and testing based on herd risk.
In dairy herds, milking management matters. Cows with suspected contagious mastitis should be identified quickly, and your vet may recommend milking them last, using dedicated equipment, or segregating them during an outbreak. Routine bulk tank surveillance and targeted testing of fresh cows, clinical mastitis cows, or high-SCC cows can help catch problems earlier.
Calf management is also important. Avoid feeding potentially contaminated waste milk unless your vet has a clear plan for how it will be handled safely. Good ventilation, reduced crowding, stress reduction, colostrum management, and prompt care for respiratory disease all help lower the odds that Mycoplasma bovis will spread and become a chronic herd problem.
There is no single prevention step that fits every farm. The best plan depends on whether the main issue is pneumonia, mastitis, arthritis, or repeated introductions from outside cattle. Your vet can help build a practical control program that matches your herd size, facilities, labor, and goals.