Staphylococcus aureus in Goats: Causes, Symptoms, and Prevention

Staphylococcus aureus is one of the most common and concerning bacterial pathogens in goats, especially dairy goats. Known for its ability to cause chronic and difficult-to-treat infections, this organism poses a serious threat to udder health, milk safety, and herd productivity. Understanding how this bacterium behaves, how it spreads, and how to manage or prevent infections is essential for anyone raising goats.

What Is Staphylococcus aureus?

Staphylococcus aureus is a gram-positive bacterium that resides on the skin and mucous membranes of animals and humans. While it often exists without causing harm, under the right conditions, it can invade tissue and cause serious infections. In goats, staph aureus is a leading cause of both subclinical and clinical mastitis, though it can also affect other body systems through skin wounds or systemic infections.

How Staph Aureus Spreads in Goats

S. aureus is primarily spread through contact, including:

• Contaminated milking equipment
• Milker’s hands or gloves
• Nursing kids
• Environmental exposure to infected bedding or surfaces

Because this bacterium can colonize the teat canal or udder tissue without causing obvious symptoms, asymptomatic carriers are a major reservoir of infection within the herd. Once a goat has a chronic infection, it often remains a source of contagion indefinitely.

Symptoms of Staph Aureus Mastitis

While many goats with S. aureus mastitis show no signs, particularly during subclinical phases, symptoms can include:

• Swelling, heat, or pain in the udder
• A cold, floppy udder (often associated with gangrenous mastitis, which can be fatal)
• A lopsided udder
• Clots, flakes, or pus in the milk
• Decreased milk production in one or both sides
• Lumps or abscesses in udder tissue
• Systemic illness in severe cases, such as fever or lethargy
• An udder half that turns black and falls off
• Sudden death

In some cases, S. aureus may also cause skin infections (pyoderma), pneumonia, arthritis, or abscesses, particularly in immunocompromised animals or those with wounds.

Diagnosis of Staph Aureus in Goats

Accurate diagnosis requires lab testing because staph aureus is not the only cause of mastitis in goats. The gold standard for diagnosing mastitis, including staph aureus, is bacterial culture of milk samples. Milk from each side of the udder should be tested separately. Additional tools include:

• CMT (California Mastitis Test): Detects elevated somatic cell counts, indicating inflammation. However, it cannot identify the specific cause. Everyone who raises goats, even meat and fiber goats, should have a CMT test kit on hand for testing because any doe in milk could wind up with mastitis.
• Milk pH testing: Some studies show that pH may rise with staphylococcal mastitis, but this is not diagnostic alone.
• Somatic cell count (SCC): Chronic S. aureus infections often result in persistently high SCCs, which is a lab test.

Negative CMT results do not rule out a staph infection, especially in subclinical or early infections. Culture remains essential for definitive diagnosis.

Treatment Challenges with Staph Aureus

Treating S. aureus mastitis in goats is notoriously difficult. The bacteria can form protective biofilms and invade deep into udder tissue, making them resistant to many antibiotics. Even when symptoms improve temporarily, the infection often recurs.

This means a goat may be negative for a couple of months and then suddenly positive again, which is why it’s important to do CMTs regularly on does that have had a previous diagnosis of staph aureus.

Antibiotic sensitivity testing is essential if treatment is attempted. Intramammary infusions and systemic antibiotics are sometimes used, but they rarely achieve a complete cure in chronic cases.

Infected does require strict segregation from non-infected does to avoid infecting others, and culling may be required in persistent cases.

Is Staph Aureus Zoonotic?

Yes. S. aureus is a zoonotic pathogen, meaning it can infect humans. Transmission may occur through:

• Direct contact with infected milk or udder secretions
• Handling abscesses or wounds
• Raw milk consumption

Of special concern is methicillin-resistant Staphylococcus aureus (MRSA), a drug-resistant form of the bacterium. While uncommon in goats, MRSA has been detected in livestock and can cause serious infections in humans. Always use gloves and follow good hygiene when handling infected animals or milk.

Can You Drink Milk from a Goat with Staph Aureus?

Milk from goats with S. aureus should not be consumed raw, even if it appears normal and tests negative on a CMT. The organism can be shed intermittently, and raw milk may carry pathogens without visible signs. Pasteurization destroys S. aureus, making the milk safe if processed properly. However, milk from goats with active mastitis should always be discarded.

When a kid nurses from a doe that has staph aureus, it may remain uninfected, or it could wind up with pneumonia, or it could become an asymptomatic carrier. It could remain asymptomatic for years, or it could freshen with mastitis. When a first freshener gets mastitis within a day or two of kidding, staph aureus should be on the list of likely culprits.

Prevention and Biosecurity

Managing S. aureus in a herd requires a combination of hygiene, monitoring, and culling:

• Use individual paper towels for cleaning teats during milking
• Dip teats with an effective disinfectant post-milking
• Milk infected animals last to avoid cross-contamination, or keep positive animals separate from negative, and do not use the same milking equipment
• Regularly culture milk from does with high SCCs or history of mastitis
• Cull chronic carriers to protect the rest of the herd
• Do not share equipment or milkers between herds unless thoroughly cleaned and disinfected

Should You Buy from a Herd with a History of Staph Aureus?

If a breeder discloses a history of staph mastitis in their herd, it’s not necessarily a dealbreaker—but caution is warranted. Ask if the animals are currently being tested, what treatment protocols are in place, and how many cases they’ve had. Ideally, milk culture results should be provided for any lactating doe. Avoid buying colostrum or milk from a herd with known infections unless pasteurized.

The Future for Goats with Staph Aureus

Staphylococcus aureus remains one of the most serious udder health threats in dairy goats. It can silently spread through a herd, causing chronic mastitis that is hard to treat and potentially dangerous to humans. Early detection, strict hygiene, and responsible culling decisions are your best tools to protect your goats and your milk supply.

If you suspect staph in your herd, work closely with a knowledgeable veterinarian experienced with managing staph aureus to develop a herd health management plan tailored to your specific situation.

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