Mycoplasma Arthritis in Cows: Joint Disease in Calves and Cattle

Mycoplasma arthritis is an infectious joint disease in cattle, most commonly associated with Mycoplasma bovis. It is seen especially in young calves, dairy calves, veal calves, and feedlot cattle. In many cases, the joint disease is part of a larger syndrome that can also include chronic pneumonia, ear infections, and tendon sheath inflammation.

Unlike many bacteria, Mycoplasma organisms do not have a normal cell wall. That matters because they can be harder to grow in the lab and may not respond well to some commonly used antibiotics. The infection often reaches the joints after spreading through the bloodstream from the respiratory tract, milk, or another infected site.

Affected calves may develop polyarthritis, meaning several joints are painful and swollen at the same time. These calves can become very lame, spend more time lying down, and fall behind in growth. Some adult cattle can be affected too, especially in herds dealing with Mycoplasma mastitis or widespread respiratory disease.

This is not a condition to monitor casually at home. If a calf or cow has joint swelling, marked lameness, fever, or trouble rising, your vet should evaluate the animal and the herd situation promptly.

The main cause is Mycoplasma bovis, a contagious bacterial pathogen that can spread within a herd. Calves may be exposed through respiratory secretions, close contact with infected cattle, or milk from infected cows. Feeding unpasteurized waste milk from cows with Mycoplasma mastitis is a recognized risk for calf exposure.

In many calves, the infection starts in the respiratory tract and then spreads through the bloodstream to joints, tendon sheaths, or the middle ear. That is why arthritis often shows up with chronic pneumonia or otitis. Stressors such as transport, commingling, poor ventilation, crowding, and inadequate colostrum management can increase the chance that exposed calves become sick.

Herd-level patterns matter. Mycoplasma arthritis may appear in operations that also have recurring calf pneumonia, ear infections, or hard-to-control mastitis in adult cows. Because some cattle can carry the organism without obvious signs, the source is not always easy to identify without testing.

Not every swollen joint is caused by Mycoplasma. Trauma, navel ill, other septic arthritis bacteria, and developmental joint disease can look similar. Your vet will help sort through those possibilities before making a treatment and management plan.

Diagnosis starts with a careful physical exam and herd history. Your vet will look for joint swelling, pain, fever, pneumonia, ear disease, and patterns affecting multiple calves or groups. A history of Mycoplasma mastitis, chronic respiratory disease, or feeding waste milk can raise suspicion.

Testing often includes joint fluid sampling for cytology, PCR, and sometimes culture. PCR is especially useful because Mycoplasma can be difficult to grow and may require special media and handling. In some cases, your vet may also recommend samples from the respiratory tract, milk, ear fluid, or tissues from a necropsy to confirm the organism and understand how it is moving through the herd.

Imaging such as radiographs or ultrasound may help assess joint damage, fluid accumulation, or tendon sheath involvement. Bloodwork is less specific, but it can support the overall picture and help rule out other problems.

Because this disease can become chronic and herd-wide, diagnosis is often about both the individual animal and the operation. A confirmed diagnosis helps your vet discuss realistic treatment goals, isolation steps, and prevention changes for the rest of the cattle.

Prevention focuses on herd management and biosecurity, because once Mycoplasma is established, control can be difficult. Work with your vet on calf flow, ventilation, stocking density, and colostrum management. Reducing stress and respiratory disease pressure lowers the chance that exposed calves will go on to develop pneumonia-arthritis syndrome.

Milk management is a major point. Avoid feeding raw waste milk from cows with suspected or confirmed Mycoplasma mastitis to calves. Many herd programs instead use milk replacer, pasteurized milk, or other lower-risk feeding strategies recommended by your vet. In dairy herds, rapid identification and segregation or removal of cows with Mycoplasma mastitis may also reduce spread.

Biosecurity matters when bringing in new cattle or commingling calves from multiple sources. Purchased animals can introduce the organism without obvious signs. Quarantine, source control, and careful movement planning are practical tools, especially for dairies, calf raisers, and feedlots.

Vaccines for Mycoplasma bovis are commercially available in some settings, but published references note that efficacy has not been clearly demonstrated. That means vaccination should be viewed as a possible herd-level discussion point with your vet, not a stand-alone solution. Consistent monitoring, early testing, and prompt response to pneumonia, ear infections, mastitis, or swollen joints remain the backbone of prevention.