🧫 What Is Brucellosis in Cattle?
Brucellosis (also known as Bang’s disease) is a contagious bacterial infection caused by Brucella abortus.
It primarily affects cows, bulls, and bison, leading to abortions, weak calves, infertility, and reduced milk production.
Brucellosis is also a zoonotic disease — meaning humans can get infected, usually by contact with infected animals or by drinking unpasteurized milk. In people, it causes undulant fever, a chronic flu-like illness.
In the United States, brucellosis is a federally regulated disease, monitored by the USDA Animal and Plant Health Inspection Service (APHIS). Thanks to aggressive eradication programs, the U.S. has nearly eliminated the disease from domestic cattle — but cases still occur, especially in wildlife reservoirs like bison and elk in the Greater Yellowstone Area.
⚠️ How Brucellosis Spreads
The Brucella bacteria survive inside cells, which makes them difficult to eliminate. Infection typically spreads through:
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Contact with aborted fetuses, placentas, or uterine fluids
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Contaminated bedding, feed, or water
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Milk, colostrum, or vaginal discharge
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Semen from infected bulls
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Wildlife-to-cattle transmission (especially from infected bison or elk)
Cows that recover often become lifelong carriers, shedding bacteria intermittently.
🩺 Clinical Signs in Cattle
Infected herds may show no signs at first, but over time, you might notice:
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Abortions during the last trimester
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Retained placenta and uterine infection
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Birth of weak or stillborn calves
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Reduced fertility and longer calving intervals
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Decreased milk yield
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Orchitis or epididymitis in bulls (swollen testicles or infertility)
Because symptoms overlap with other reproductive diseases, lab testing is essential for confirmation.
🔬 Diagnosis — How Vets Confirm Brucellosis
In the U.S., brucellosis is a reportable disease, meaning any positive test must be reported to state and federal animal health authorities.
Common diagnostic tools include:
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Blood Tests (Serology):
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Rose Bengal Test (RBT) for screening
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Complement Fixation Test (CFT) or ELISA for confirmation
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Bacterial Culture:
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Isolation of Brucella abortus from aborted materials or milk (done in biosafety-level labs).
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PCR (Molecular Tests):
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Detects bacterial DNA quickly and accurately.
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Veterinarians also investigate herd history, including abortion patterns, wildlife exposure, and purchase records.
💊 Treatment — Why Antibiotics Aren’t Enough
Unfortunately, treating brucellosis in cattle with antibiotics doesn’t cure the infection.
Because Brucella hides inside cells, it’s extremely difficult to eradicate completely. Infected animals can remain carriers even after therapy.
👉 Therefore, the USDA recommends “test and removal” (culling) of positive cattle, combined with strict biosecurity and vaccination to prevent new infections.
💉 Vaccination & Prevention in the U.S.
Vaccination remains the best preventive measure in regions at risk.
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RB51 vaccine is the only approved Brucella abortus vaccine in the United States.
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It’s a live, rough strain vaccine that does not interfere with most serologic tests.
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Typically given to heifer calves between 4 and 12 months old.
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Vaccination must be administered by an accredited veterinarian and recorded officially with an ear tattoo (RAB).
Other key prevention measures:
✅ Isolate and test all new cattle before adding them to the herd
✅ Dispose of aborted materials safely (burn or bury deeply)
✅ Use protective gloves and disinfect calving areas
✅ Prevent contact between cattle and wild elk or bison
✅ Never consume unpasteurized milk or cheese products
💰 Economic & Public Health Importance
Brucellosis can cause serious economic losses from abortions, decreased milk yield, infertility, and trade restrictions.
In humans, Brucella abortus can cause prolonged fever, fatigue, arthritis, and miscarriage — making it a major public health concern for veterinarians, ranchers, and dairy workers.
Thanks to U.S. control programs, domestic cattle herds are officially brucellosis-free in nearly every state, but continued vigilance — especially near wildlife reservoirs — is essential.
🧠 Veterinarian Insights
“I’ve seen firsthand how a single brucellosis-positive cow can disrupt an entire herd’s productivity and trade status. Early detection, accurate testing, and preventive vaccination are worth far more than reactive treatment. In areas bordering Yellowstone, I always stress wildlife management as part of herd biosecurity.”
— Dr. [Your Name], DVM — Bovine Health Specialist
🐮 Frequently Asked Questions (FAQ)
1. Can humans get brucellosis from cattle?
Yes — through contact with infected tissues or raw milk. Always wear gloves and pasteurize milk.
Brucellosis in human can cause severe infection.
2. Is brucellosis curable in cattle?
No. Infected animals remain carriers; control relies on testing, culling, and vaccination.
3. Which states in the U.S. still face brucellosis risk?
Mainly states near the Greater Yellowstone Area — parts of Wyoming, Montana, and Idaho — due to infected wildlife.
4. Is the RB51 vaccine safe?
Yes, when administered properly by veterinarians. However, humans should avoid accidental needle exposure since RB51 can cause infection.
🧾 References (Trusted U.S. Sources)
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USDA-APHIS. “Brucellosis (Brucella abortus) Eradication Program.”
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CDC. “Brucellosis in Humans and Animals.”
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Merck Veterinary Manual. “Brucellosis in Cattle.”
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National Association of State Public Health Veterinarians (NASPHV).
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WOAH (World Organisation for Animal Health) Terrestrial Manual, Chapter on Brucella abortus.
🏁 Key Takeaway
Brucellosis in cattle is largely controlled in the U.S., but wildlife reservoirs keep it a persistent threat.
The best defense is strict biosecurity, official testing, vaccination of heifers, and avoiding unpasteurized milk products.
Healthy herds protect not just your farm — but the public as well.