Brucellosis Laws in Wyoming: Vaccination, Testing, Movement Rules, and Penalties

Wyoming sits at the center of the most active brucellosis risk zone in the United States. The Greater Yellowstone Area — which includes northwest Wyoming — is the only region in the country where Brucella abortus remains endemic in wild elk and bison, and that reality shapes every layer of the state’s livestock regulatory framework. If you raise cattle or bison in Wyoming, import breeding stock, or move animals across state lines, you are operating under a specific and enforceable set of rules that differ meaningfully from most other states.

This guide walks you through Wyoming’s brucellosis classification status, who must vaccinate and when, what testing applies inside and outside the Designated Surveillance Area, how movement is regulated both in-state and interstate, what reporting and quarantine obligations you carry, and what penalties follow a violation.

What Is Brucellosis and Why It Is Regulated in Wyoming

Brucellosis is a bacterial disease caused by organisms of the genus Brucella. It affects multiple animal species and can spread to humans, making it one of the most consequential zoonotic diseases in livestock agriculture. For cattle and bison producers, the primary concern is Brucella abortus, the species responsible for bovine brucellosis and the target of the national eradication program that has been ongoing since 1934.

In infected cattle, the disease causes reproductive failure — most notably late-term abortions, stillbirths, and the birth of weak calves. Infected cows frequently retain their placentas, and bulls may develop orchitis. Milk production drops in affected dairy herds. The bacteria shed during abortions and in milk can survive in the environment for weeks, making contaminated premises a persistent risk to other animals.

The disease causes decreased milk production, weight loss in animals, loss of young, infertility, and lameness. There is no known effective treatment. Depopulation of infected and exposed animals is the only effective means of disease containment and eradication.

Brucellosis can also spread to humans as undulant fever. According to the Wyoming Department of Health, human death from the disease is rare, occurring in less than 2% of cases.

Wyoming’s regulatory framework exists precisely because of the state’s unique geographic position. The disease is limited in distribution to northwestern Wyoming and adjoining portions of Idaho and Montana, where it primarily affects elk and bison. The prevalence of brucellosis can be quite high — up to 75% in bison — yet there is no evidence that brucellosis has noticeable impacts on wildlife populations. The primary management concern is the possible transmission of brucellosis from elk or bison to domestic cattle. States with infected cattle herds suffer economic hardships, and the threat to cattle results in ongoing friction among wildlife management agencies, ranchers, and federal agencies.

Wyoming’s Brucellosis Classification Status

Under the federal classification system administered by USDA APHIS, Wyoming is currently listed as a Class Free state — the highest possible designation. The full list of Class Free states includes Wyoming alongside all other U.S. states and territories.

That status has not always been stable. The U.S. Department of Agriculture previously revoked Wyoming’s classification as a brucellosis-free state, which meant that many of the cattle leaving the state had to first be tested and certified as brucellosis-free. Wyoming regained its brucellosis-free status in September 2006. The reinstatement eased some of the restrictions statewide for the cattle industry, but within the brucellosis “endemic” area of northwest Wyoming, cattle producers are still required to remain vigilant for the disease.

A key federal requirement is that any Class Free state with Brucella abortus in wildlife must develop and implement a brucellosis management plan approved by the USDA APHIS Administrator in order to maintain Class Free status. Wyoming satisfies this requirement through its Chapter 2 Brucellosis Management and Mitigation rules, administered by the Wyoming Livestock Board (WLSB).

The Greater Yellowstone Area is the only known location within the United States where B. abortus is still present, specifically in the area’s wild bison and elk. While the disease is endemic in wild elk and bison in the GYA, it occurs in livestock herds only occasionally as a spillover event from wildlife exposures. Since 2006, all affected cattle and bison herds detected within the GYA have been attributed to wild elk spillover.

You can review how other states manage their own classification obligations by reading about brucellosis laws in Nebraska and brucellosis laws in Nevada, both of which operate under the same federal Class Free framework.

Vaccination Requirements for Cattle and Bison in Wyoming

Wyoming’s vaccination rules are tiered. Your obligations depend on whether your animals are located inside or outside the Designated Surveillance Area. The DSA covers the northwest portion of the state, where wildlife-to-livestock spillover risk is highest.

Statewide Vaccination Rule

In the state of Wyoming, sexually intact heifers must be vaccinated for brucellosis by one year of age. This is a statewide requirement that applies regardless of whether your operation is inside or outside the DSA. Under Wyoming’s Chapter 2 rules, “Calfhood Vaccination Eligible” means sexually intact female Bovinae four through twelve months of age.

DSA-Specific Vaccination Deadline

In the state of Wyoming, sexually intact heifers must be vaccinated for brucellosis by one year of age. In addition, heifers residing in Wyoming’s DSA that are brucellosis vaccine eligible — four months of age or older — must be brucellosis vaccinated by February 1 each year. This annual February 1 deadline applies specifically to DSA-located animals and is enforced by the WLSB.

Adult Vaccination

Adult vaccination of female Bovinae requires written approval. The owner of the Bovinae must make a request to the Wyoming State Veterinarian, who may grant approval to the herd veterinarian authorized to perform the adult vaccination. Adult booster vaccination is allowed with prior approval, but it is not a routine procedure you can arrange without going through the State Veterinarian’s office first.

Imported Animals

All breeding cattle and bison entering Wyoming must be accompanied by a proper health certificate showing evidence of a negative blood test for brucellosis made within thirty days prior to entry, or evidence of being officially vaccinated by a licensed veterinarian during calfhood against brucellosis. Breeding cattle and bison originating from brucellosis-free areas and from certified brucellosis-free herds entering Wyoming may be exempt from this section but must still be accompanied by a proper health certificate.

Testing Requirements for Cattle and Bison in Wyoming

Testing obligations in Wyoming are closely tied to your location, the purpose of movement, and whether a change of ownership is involved. The DSA carries the most extensive testing requirements in the state.

Who Is Test-Eligible

Test-eligible animals are sexually intact females 12 months of age or older. This applies both to in-state animals subject to DSA rules and to animals being moved or changing ownership.

DSA Testing Triggers

Within the DSA, testing is required before a change of ownership, movement out of the DSA, or interstate movement. The testing timeframe is within 30 days before movement, or one time from August 1 through January 31 if the movement occurs during that window.

Required brucellosis surveillance for specified cattle in the DSA includes testing prior to leaving the DSA and within 30 days prior to change of ownership. This dual trigger — movement out of the DSA and change of ownership — means that a sale of DSA-origin cattle almost always requires a current negative test.

Statewide Change-of-Ownership Testing

Statewide, brucellosis testing is required prior to change of ownership for any intact female over 12 months of age. This rule applies across Wyoming, not just in the DSA. If you are selling or transferring breeding females anywhere in the state, you must have a current negative brucellosis test result on file.

Suspicious Reactions and Retesting

Animals that are tested in Wyoming and give a suspicious reaction to an official blood test for brucellosis must be quarantined in a pen at the farm or ranch of origin and subjected to an official retest made not less than thirty nor more than sixty days from the date of collecting the blood sample with the suspicious reaction. They must then be dealt with in a manner consistent with procedures outlined in the USDA Brucellosis Uniform Methods and Rules (UMR).

Testing Exemptions

Exemptions from testing requirements apply to animals moving directly to slaughter or to an approved feedlot, or to a state that accepts non-vaccinates. Additionally, breeding cattle and bison entering Wyoming for the purpose of feeding only may be exempt from standard brucellosis test requirements if they are placed under quarantine by the rules and regulations promulgated by the Wyoming Livestock Board.

For a comparison of how testing obligations work in neighboring states, see the guides on brucellosis laws in Michigan and brucellosis laws in Minnesota.

Interstate and Intrastate Movement Rules in Wyoming

Wyoming’s movement rules operate on two levels: the federal framework that governs interstate shipments from a Class Free state, and the state-level DSA rules that govern movement within Wyoming’s own borders.

Interstate Movement from Wyoming

Restrictions on moving cattle and bison interstate become less stringent as a state or area approaches or achieves Class Free status. Because Wyoming holds Class Free status, most cattle moving out of state are not subject to the pre-movement testing requirements that would apply if Wyoming were classified as Class A or lower.

However, DSA-origin animals carry additional obligations regardless of Class Free status. Testing within the DSA is required before interstate movement, which means that animals originating from the DSA must have a current negative test before they can leave Wyoming, even when the destination state’s general import rules would not require it.

For interstate shipments under a VS Form 1-27, a person may not transport interstate animal shipments under a specified restriction by the USDA APHIS VS into or through Wyoming without prior approval from the Wyoming State Veterinarian.

Intrastate Movement Within Wyoming

The DSA boundary functions as an internal regulatory border. Moving cattle out of the DSA — even to another Wyoming county — triggers the same testing requirements as moving animals out of state. Both Sublette and Park counties are part of Wyoming’s Brucellosis Designated Surveillance Area, which requires increased surveillance and vaccination for the disease.

Out-of-state origin commuter herds leaving Wyoming are subject to a requirement that 20 percent of the herd be tested. Commuter permit holders must ensure that the permit accompanies the return shipment, and commuter permits do not waive brand inspection requirements.

Importing Breeding Cattle and Bison into Wyoming

All breeding cattle and bison entering Wyoming must be accompanied by a proper health certificate showing evidence of a negative blood test for brucellosis made within thirty days prior to entry, or evidence of being officially vaccinated by a licensed veterinarian during calfhood against brucellosis. Animals imported for feeding only may qualify for a quarantine-based exemption under W.S. 11-19-403, but that exemption requires formal placement under quarantine — it is not automatic.

Wyoming’s Chapter 8 Import Rules, effective October 2025, set out the complete requirements for all species entering the state, including specific brucellosis provisions for cattle, bison, and swine.

You can also review how movement rules compare in other states by reading about brucellosis laws in Missouri.

Reporting and Quarantine Requirements in Wyoming

Wyoming operates a mandatory reporting system for brucellosis and other designated diseases. If you identify or suspect brucellosis in your herd, you are legally required to report it — and the WLSB has broad authority to impose quarantine once a case is confirmed or suspected.

Reportable Disease Status

The WLSB maintains a list of animal diseases called the “Reportable Disease List” that are required to be reported to the state veterinarian when they are identified. These diseases are important for many reasons including their impact on herd health, public health as zoonotic diseases, and the economics and marketability of the Wyoming livestock industry. Brucellosis is included on this list.

Quarantine of Reactor Animals

The Wyoming State Veterinarian, or an authorized representative, shall issue a quarantine of all brucellosis reactor domestic Bovinae and the herd associated with the reactor. Brucellosis reactor domestic Bovinae must be officially identified as per the Brucellosis UMR.

All reactor domestic Bovinae and other domestic Bovinae in the associated herd shall be held subject to quarantine and a Brucellosis Affected Herd Plan. This means the entire herd — not just the confirmed reactor animals — comes under quarantine once a positive is identified.

Quarantine of Exposed Animals

The Wyoming State Veterinarian, or an authorized representative, shall issue a quarantine of all brucellosis exposed domestic Bovinae and the associated herd, which shall be held subject to the quarantine and shall not be offered for sale or given away except with written permission of the Wyoming State Veterinarian or an authorized representative.

What Quarantine Means in Practice

Quarantined herds will remain under quarantine until they pass a series of tests showing they are negative for brucellosis. In the meantime, movement of the animals is restricted. Some cattle markets and grazing ranges are off limits for quarantined cattle. According to Wyoming Public Media reporting, the total cost can reach approximately $140,000 for a 400-cow herd.

The affected herd is required to participate in serial testing to meet the requirements for quarantine release. Testing of affected herds is a cooperative effort between herd owners, private veterinary practitioners, WLSB personnel, and USDA APHIS Veterinary Services personnel.

Wildlife Surveillance Role

In the northwestern part of the state where brucellosis is found, the Wyoming Game and Fish Department conducts annual surveillance to monitor prevalence of the disease. Each year, the Wyoming Game and Fish Department offers a hunting gear raffle for hunters who submit samples from their harvested game for brucellosis testing. This raffle is the department’s way of incentivizing hunters to submit samples and thank those who do. Hunters play a critical role in the ability to monitor brucellosis in Wyoming.

Understanding quarantine procedures in comparable livestock states can provide useful context. See the guide on brucellosis laws in Michigan for a state that also manages wildlife-linked disease spillover risk. Wyoming producers may also find it useful to review other Wyoming-specific animal law resources such as leash laws in Wyoming and dog bite laws in Wyoming as part of a broader understanding of the state’s animal regulatory framework.

Penalties for Brucellosis Violations in Wyoming

Wyoming’s penalty framework for brucellosis violations operates at both the state and federal level. The statutory basis for the WLSB’s authority is found in Wyoming Statute Title 11, and violations of the board’s Chapter 2 rules carry penalties outlined under W.S. 11-19-101.

Statutory Authority and Rule Violations

Pursuant to Wyoming Statute §§ 11-18-103(a)(v) and 11-32-102, the Wyoming Livestock Board promulgates its import and animal health rules. Chapter 2 of those rules explicitly states that penalties for a violation apply as outlined in W.S. 11-19-101. Violations of brucellosis rules — including failure to vaccinate, failure to test before movement or change of ownership, unauthorized movement of quarantined animals, and failure to report a suspected case — are all subject to enforcement under this framework.

Financial Consequences of Quarantine

Beyond formal statutory penalties, the financial consequences of a brucellosis event are severe even when a producer is cooperating fully with authorities. Brucellosis quarantine can have significant financial impacts on ranchers. There are brucellosis testing costs and often a loss of some stock. Additionally, some markets and grazing ranges are off limits for quarantined herds. All-in-all, the cost can reach approximately $140,000 for a 400-cow herd.

Indemnity and Compensation

Brucellosis herd mitigation plans offered by the WLSB may cover the costs of annual testing and provide further suggestions to prevent your herd from becoming infected. Federal indemnity payments may also be available through USDA APHIS for depopulated animals, but those payments are contingent on compliance with the affected herd plan and cooperation with the epidemiological investigation. Producers who moved animals in violation of quarantine rules or failed to report a reactor animal may not be eligible for indemnity.

Statewide Consequences of Individual Noncompliance

The consequences of widespread noncompliance extend well beyond individual producers. Any Class Free state with Brucella abortus in wildlife must maintain a brucellosis management plan approved by the USDA APHIS Administrator in order to maintain Class Free status. If Wyoming’s enforcement record deteriorates or if spillover events are not properly managed, USDA APHIS has the authority to reclassify the state. That reclassification would impose new testing and movement requirements on every cattle and bison producer in Wyoming — a statewide cost triggered by failures at the individual level.

For additional context on how Wyoming regulates other aspects of livestock and animal ownership, see the guides on goat ownership laws in Wyoming, beekeeping laws in Wyoming, and kennel zoning laws in Wyoming. Producers interested in how brucellosis regulation compares across the region can also review brucellosis laws in Nebraska and brucellosis laws in Missouri.

If you have questions about your specific obligations under Wyoming’s brucellosis rules, contact the Wyoming Livestock Board directly at 307-777-7515 or reach the Wyoming State Veterinarian’s office for guidance on your herd’s situation. The WLSB also maintains the official Chapter 2 and Chapter 8 rules on its animal health page, which is the authoritative source for current regulatory text.