Contagious Agalactia in Goats: Mastitis, Arthritis, and Eye Infection Signs

Contagious agalactia is an infectious disease syndrome of sheep and goats caused mainly by Mycoplasma agalactiae. In goats, closely related mycoplasma species can cause a very similar illness too. The disease is best known for the classic triad of mastitis, arthritis, and eye inflammation, especially keratoconjunctivitis. In some herds, pneumonia and illness in kids can also occur.

The word agalactia means loss of milk. In lactating does, that can look like a sudden drop in production, poor milk letdown, or milk that becomes watery, clotted, or otherwise abnormal. Some goats recover enough to feel better but continue to have reduced milk output or become long-term carriers, which is one reason herd-level control matters.

For pet parents and producers alike, this disease can be frustrating because signs vary. One goat may show udder changes first, another may limp from joint infection, and another may have red, painful eyes. If more than one goat is affected, especially after a new arrival or shared milking equipment, your vet may become concerned about a contagious mycoplasma problem rather than a routine case of mastitis or pinkeye.

Contagious agalactia is caused by mycoplasmas, a group of bacteria-like organisms that do not have a normal cell wall. Mycoplasma agalactiae is the main classic cause, but goats can also develop a similar syndrome from M. capricolum subsp. capricolum, M. mycoides subsp. capri, and M. putrefaciens. These goat-associated organisms may also be linked with pneumonia.

Spread usually happens through infected milk, udder secretions, eye discharge, close contact, and contaminated milking equipment or hands. New or returning animals are a common way contagious diseases enter a herd. Carrier animals may look normal but still shed organisms, which makes outbreaks hard to predict.

Risk tends to be higher in dairy settings, during lactation, and anywhere goats are housed or milked closely together. Stress, transport, kidding, and mixing groups may also make transmission easier. Because several other diseases can mimic parts of this syndrome, your vet will usually consider contagious agalactia alongside other causes of mastitis, arthritis, pinkeye, and chronic herd problems.

Diagnosis starts with a careful history and physical exam. Your vet will ask about recent kidding, milk production changes, new herd additions, shared nursing or milking equipment, and whether other goats have eye, joint, or respiratory signs. The pattern matters. A single mastitis case can happen for many reasons, but mastitis plus arthritis or eye disease in multiple goats is more suspicious for a contagious mycoplasma outbreak.

Testing usually focuses on the body site showing signs. Useful samples from live goats include milk or udder secretions, joint fluid from swollen joints, and eye swabs from goats with conjunctivitis or corneal changes. PCR can help confirm infection quickly, and culture may also be used, though mycoplasmas need special handling and can be harder to grow.

Your vet may also recommend milk culture, cytology, or additional testing to rule out other causes of mastitis or lameness. In deaths or severe herd outbreaks, necropsy and tissue sampling can be very helpful. Because serology can be less definitive on its own, especially in areas where the disease is uncommon, your vet may want direct organism detection before making herd-level decisions.

Prevention starts with biosecurity. The most important step is to be cautious about introducing new animals. Work with your vet before purchase, ask about herd health history, and quarantine new or returning goats before mixing them with the resident herd. A practical isolation period is often about 4 weeks, with close observation for udder, eye, respiratory, and lameness signs.

Milking hygiene also matters. Milk healthy goats first, then suspect or affected goats last. Clean and disinfect milking equipment between animals when possible, avoid sharing towels, and wash hands or change gloves between does with udder problems. Kids should not nurse from suspect does unless your vet specifically advises it.

If contagious agalactia is suspected, fast separation of sick animals can reduce spread. Your vet may recommend testing exposed goats, reviewing replacement-animal policies, and making a long-term plan for chronic shedders. On farms with repeated problems, prevention is usually less about one product and more about screening, quarantine, sanitation, and herd-level decision making.