World Agriculture Directory: the home of the world's largest agriculture database. Fastest way to find events, farms and agribusiness that suit your needs. Agriculture Event Directory

Cattlemen Hall of FameBeef cattle barons, cowboys, breeders and builders from around the world

Beef Industry Innovators

Brucellosis Eradication: How U.S. Cattle Herds Cut Disease From 124,000 to Single Digits

A decades-long state and federal campaign of testing, vaccination and slaughter took bovine brucellosis from a national burden to a few spillover cases.

What Is Bovine Brucellosis?

Brucellosis in cattle is caused by the bacterium Brucella abortus, which also infects bison. The USDA Animal and Plant Health Inspection Service says the disease has been in the United States since the 1930s. For a cow-calf producer, the practical cost is reproductive: infected animals are a risk to the herd's calf crop, and the herd can lose its market access.

APHIS estimated annual economic losses at more than $400 million in 1952. Today, according to the APHIS bovine brucellosis page, that figure is under $1 million.

A Cooperative State-Federal Program

The eradication effort is a cooperative state-federal program run by APHIS. The structure matters: states controlled animal movement and herd testing within their borders, while federal officials set standards and funded work. Trade sources often date federal brucellosis work to the mid-1930s, though the APHIS page itself gives no start year, so readers should treat 1934 as a commonly cited date and not an official one.

The results are measurable. According to APHIS, affected herds fell from about 124,000 in 1956 to about 700 in 1992, and the number of affected domestic herds is in the single digits today. The APHIS program document and a range management fact sheet describe the same disease and its management.

Testing at Slaughter and Herd Surveillance

Surveillance continues even though the disease is rare. APHIS tests roughly half a million animals at slaughter each year, and the estimated prevalence is 0.002 percent. For fiscal year 2025, Idaho had the most tests at 205,040 in total, followed by Oregon with 31,983, Washington with 29,870, Wyoming with 27,196 and California with 26,123.

These numbers reflect geography. Idaho, Wyoming and the neighboring states sit close to the one place where the disease persists in wildlife.

Vaccination: RB51 and Calfhood Protection

Vaccination supported the testing program. RB51, licensed in 1996, is about 70 to 80 percent effective, according to APHIS. It is licensed only for non-pregnant female cattle aged 4 to 12 months and is not yet licensed for bison. About 3.5 million calves are vaccinated each year. APHIS also notes that RB51 is resistant to rifampin and penicillin, a detail that matters for people handling the vaccine.

What Made It Work

The program worked because it combined detection, vaccination and movement rules over decades, and because producers, states and federal agencies shared costs and responsibility. The result was a steep, documented decline in infected herds.

  • Shared authority: states and the federal government split the work, which let enforcement follow local conditions.
  • Surveillance at slaughter: testing about half a million animals a year finds problems that herd owners might not.
  • Vaccinating calves: RB51 is licensed for heifers aged 4 to 12 months, which targets the animals that will carry the next generation.
  • Staying power: infected herds fell from about 124,000 in 1956 to about 700 in 1992, a drop that took more than three decades.
  • Declared losses: annual economic losses fell from more than $400 million in 1952 to under $1 million.
  • Limits: the program cannot easily clear wildlife, and the vaccine is not complete protection.

The Greater Yellowstone Problem

Wild bison and elk in the Greater Yellowstone Area are the last remaining U.S. reservoir of the disease, per APHIS. Transmission risk is highest when elk or bison calve near grazing or feeding livestock, and occasional spillover into cattle herds in the area is the reason the national status carries an exception.

That makes brucellosis a land-use and wildlife-management issue as well as a veterinary one. Ranchers near the park work with state and federal agencies on timing, fencing, vaccination and testing.

Why It Matters Today

Brucellosis freedom is an asset in export and interstate trade, and it is easy to forget because it has been quiet for decades. The record shows what sustained public and private cooperation can accomplish. For more on ranch history, see the ranching pages on farm.FM, or read a farm.FM story on herd health.

Timeline

  1. 1930sBovine brucellosis present in the United States, according to APHIS.
  2. 1952Annual economic losses exceed $400 million.
  3. 1956About 124,000 herds affected.
  4. 1992Affected herds fall to about 700.
  5. 1996RB51 vaccine licensed.
  6. TodayAffected domestic herds in single digits; all states brucellosis-free apart from Greater Yellowstone spillover.

Frequently asked questions

What causes brucellosis in cattle?

Bovine brucellosis is caused by the bacterium Brucella abortus, which infects cattle and bison. It has been in the United States since the 1930s, according to USDA APHIS.

Is brucellosis eradicated in the United States?

Nearly. All 50 states, Puerto Rico and the U.S. Virgin Islands are brucellosis-free, except for occasional spillover into livestock near the Greater Yellowstone Area, where wild bison and elk remain a reservoir.

How effective is the RB51 vaccine?

APHIS says RB51 is about 70 to 80 percent effective. It was licensed in 1996 for non-pregnant female cattle aged 4 to 12 months, and about 3.5 million calves are vaccinated annually.

Sources and further reading

Profiles are compiled from public sources and reviewed against them. See our editorial policy to suggest a correction.

More from the hall