Bovine Tuberculosis Testing Requirements in California: What Cattle Owners Must Know
August 10, 2026
If you raise, sell, or move cattle in California, bovine tuberculosis testing requirements are not optional paperwork — they are a legal condition of doing business with livestock in this state. A single infected animal found during a routine slaughter inspection can trigger a herd-wide quarantine, months of retesting, and restrictions on where your cattle can go next.
This guide walks through how California classifies its TB risk status, which animals must be tested, which tests regulators accept, and what happens if a test comes back positive. Whether you run a dairy, a beef operation, or move bison and cervids across state lines, understanding these rules before you need them can save you time, money, and a herd under lockdown.
What Is Bovine Tuberculosis and Why It Is Regulated in California
Bovine tuberculosis is caused by Mycobacterium bovis, an organism very similar to the bacteria causing human tuberculosis. It can affect cattle, bison, deer, elk and other warm-blooded species, and can be fatal. Because the disease spreads slowly but persistently through a herd, states run coordinated eradication programs rather than leaving control to individual ranchers.
The disease matters beyond the barn because it is zoonotic. Bovine tuberculosis is a zoonotic disease, meaning humans can be infected by exposure to infected animals or animal products. Pasteurization has sharply cut human exposure through dairy, but humans can still become infected by drinking raw milk or eating unpasteurized cheese from TB-infected animals. Notably, the incidence of the M. bovis strain of TB in people is higher in California compared to the rest of the U.S., likely due in part to the consumption of unpasteurized cheese, such as the popular queso fresco from Mexico, which has been found to contain M. bovis and should be considered unsafe.
Important Note: Bovine tuberculosis testing protects herd health and public health simultaneously. If you handle raw milk products, pair TB compliance with the same attention you would give rabies vaccine requirements in California, since both programs exist because the diseases cross from animals to people.
To manage this risk, the best way for cattle producers to prevent bovine tuberculosis is to maintain a closed herd or isolate and test purchased additions and cattle re-entering the herd, prevent contact with cattle of Mexican origin, arrange professional diagnostic workup of sick animals, maintain accurate records of animal identification and movements, and establish a tuberculosis testing policy for employees. The California Department of Food and Agriculture (CDFA) runs this program jointly with the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service, which sets the national testing standards CDFA enforces at the state level.
California’s TB Classification Status and Risk Zones
The U.S. Department of Agriculture (USDA) maintains a monitoring system that classifies states based on the presence of bovine TB within a state’s cattle population. States, or zones within states, are classified in five categories: Accredited Free, Modified Accredited Advanced, Modified Accredited, Accreditation Preparatory and Non-Accredited. Each tier carries different testing obligations for cattle leaving the state.
| Classification Tier | What It Generally Means |
|---|---|
| Accredited Free | Lowest TB prevalence; cattle and bison can move interstate without a federal TB test requirement |
| Modified Accredited Advanced | Low prevalence, but some interstate movement conditions apply, such as pre-movement testing for sexually intact animals |
| Modified Accredited | Higher prevalence than Advanced tier; stricter herd and individual testing before movement |
| Accreditation Preparatory | State working toward Modified Accredited status; whole-herd testing typically required |
| Non-Accredited | Highest prevalence tier; most restrictive movement and testing rules |
California has not always held the top tier. APHIS had listed California as an accredited-free state for bovine tuberculosis, but an epidemiological investigation of a tuberculosis-positive cow found through slaughter surveillance in December 2007 resulted in the confirmation of an affected dairy herd, and as the investigation continued, two additional affected dairy herds were identified, meaning California no longer met the requirements for accredited-free status. Later cases followed: bovine TB was detected and subsequently eradicated in one herd in San Bernardino County in 2009, three in San Bernardino County in 2011, and one in Tulare County in 2013.
After years of remediation, USDA’s Animal and Plant Health Inspection Service completed its review of California’s TB eradication program and determined the state met the requirements for accredited free status, following a program that included testing 1,444,122 cattle in several hundred herds. This interim rule was effective August 8, 2016, and California has held Accredited Free status since that reinstatement based on the most recent Federal Register determination and CDFA program updates. The federal framework also allows for a State to request partitioning into specific geographic regions or zones with different status designations, commonly referred to as split-State status, if bovine tuberculosis is detected in a portion of a State — a mechanism California has not currently invoked statewide.
Who Must Test and Which Animals Are Covered in California
Testing obligations depend on the animal’s species, sex, age, and intended use rather than applying uniformly to every bovine in the state. The following categories are commonly subject to bovine TB testing requirements in California:
- Sexually intact dairy cattle over six months of age entering the state
- Sexually intact beef cattle six months and older moving from non-TB-Free zones
- Bison, water buffalo, and yaks over six months of age
- Cervidae such as deer, elk, and moose held in captive herds
- Camelids, which require a specialized axillary test rather than the standard cattle test
- All cattle presented for slaughter, which are inspected regardless of prior testing history
Testing itself is performed by specific categories of veterinarians. California accredited veterinarians, the California Department of Food and Agriculture (CDFA), or United States Department of Agriculture (USDA) veterinarians perform the TB screening test, the caudal fold test. Not every accredited vet can run every test, though: you must be certified to perform the Single Cervical Tuberculin (SCT) test in cervidae and the axillary test in camelidae, which involves training in proper test procedures by a regulatory veterinarian.
Beyond live-animal testing, surveillance never really stops. The primary method of tuberculosis surveillance shifted to slaughterhouse inspection, where every bovine processed in California is examined for signs of disease. This layered approach — routine slaughter checks plus targeted live-animal testing — is why brand inspection requirements in California and TB identification rules often intersect: both depend on accurate animal identification records to trace an animal back to its herd of origin if a problem surfaces.
Approved TB Testing Methods in California
California follows the same tiered testing protocol used nationally, moving from a low-cost screening test to more definitive confirmatory diagnostics only when needed.
- Caudal Fold Test (CFT): A small amount of purified protein derivative (PPD) tuberculin is injected into the fold of skin at the base of the tail, and the test is read 72 (plus or minus 6) hours later. If negative, no further action is required; if positive, the animal is classified as a responder and requires further testing.
- Comparative Cervical Test (CCT): A Comparative Cervical Tuberculin test must be performed within 10 days, or after 60 days, of the CFT by a regulatory veterinarian, consisting of two injections in the neck skin — one bovine and one avian tuberculin extract — read 72 hours later and plotted on a scattergram to classify the animal as negative, suspect, or reactor.
- Gamma Interferon Test: An alternative whole-blood test that must be performed within three to 30 days following the CFT injection, classifying animals as negative, suspect, or reactor, with suspect animals eligible for re-bleeding within 30 days of the CFT injection.
- Single Cervical Tuberculin (SCT) Test: Used for cervidae such as deer, elk, and moose in place of the standard caudal fold approach.
- Necropsy and Laboratory Confirmation: Animal necropsy and laboratory testing, including microbiology, molecular biology, and histopathology, are needed to definitively diagnose bovine TB, using samples from lymph nodes of the head, thorax, and abdomen along with any other abnormal tissue found.
No screening test is perfect. A false positive rate of 1 to 2 percent is expected during a whole herd test, which is exactly why a single CFT responder does not automatically mean an infected animal — it means the animal needs a confirmatory test before any conclusions are drawn.
Pro Tip: Tuberculin has to be handled carefully to stay accurate. Store it away from light, keep it refrigerated, and never hold a drawn dose longer than 12 hours, since improper handling is a common cause of unreliable test readings, according to CDFA’s testing guidance for accredited veterinarians.
Interstate and Intrastate Movement Testing Requirements in California
Because California holds Accredited Free status, outbound movement is comparatively simple: cattle and bison can move to other states without the federal requirement of TB testing. Bringing animals into California is a different story, and requirements vary by cattle type.
| Animal Type | TB Test Window Before Entry | CVI Required |
|---|---|---|
| Beef cattle, 6 months and older | Within 60 days, if from a non-TB-Free zone | Yes, in most cases |
| Sexually intact dairy cattle, 6 months and older | Within 60 days before entry | Yes |
| Bison, water buffalo, and yaks, 6 months and older | Within 60 days before entry | Yes |
Specifically, cattle 6 months of age and over require a negative TB test within 60 days before entry if originating from states or zones not classified as TB Free. For dairy operations, sexually intact dairy cattle over six months of age require a negative tuberculosis test within 60 days before entering the state. The same 60-day window applies to other bovid species: bison, water buffalo, and yaks over six months require a negative tuberculosis test within 60 days before entering the state.
A Certificate of Veterinary Inspection (CVI) accompanies most of these movements. The CVI is required, and cattle must be inspected within 30 days of movement into the state. If you’re hauling cattle to meet these deadlines, coordinate testing dates with your transport schedule — reviewing livestock trailer requirements in California alongside your CVI and test paperwork prevents a compliant animal from missing its testing window simply because of a logistics delay.
These state-level entry rules sit on top of the federal framework. Under 9 CFR Part 77, cattle and bison movement conditions differ depending on the origin state’s classification tier, with additional testing or herd-accreditation documentation required for anything below Accredited Free status. It’s a similar structure to how EIA/Coggins test requirements in California govern equine movement — a mandatory pre-movement disease test tied to a specific testing window, just applied to a different disease and species.
What Happens When a Suspect or Positive Result Occurs in California
A positive CFT result does not end at the barn — it opens a formal, multi-step process. Bovine TB testing is a time-consuming, multi-step process requiring planning and coordination: first, accredited veterinarians or CDFA/USDA staff perform the caudal fold test, and cattle responding to it require secondary tests performed by CDFA or USDA personnel.
Secondary confirmation follows one of two paths. Secondary tests include the gamma interferon blood test or the comparative cervical test, and animals positive to either secondary test may be retested or are examined for lesions postmortem. Importantly, testing doesn’t happen in isolation — all cattle on the premises are quarantined until all testing is complete. This whole-premises quarantine, rather than isolating just the responding animal, is one of the more disruptive parts of the process for producers.
If a necropsy confirms infection, laboratory work identifies the exact pathogen. As other bacteria can also absorb the acid-fast stain used in histological examination, further diagnostics are necessary, and a polymerase chain reaction (PCR) test can be performed on samples containing acid-fast bacteria to confirm Mycobacterium bovis specifically.
Important Note: A “suspect” classification is not the same as a confirmed positive. Suspect animals under the gamma interferon protocol can be re-bled within 30 days of the original CFT injection, and many suspect classifications resolve without a confirmed diagnosis after follow-up testing.
Quarantine and Herd Depopulation Rules in California
California’s recent history shows how quarantine and remediation actually play out. When bovine TB was detected in a dairy herd in Tulare County on February 6, 2013, diagnosed during trace investigation testing after a suspicious mass in a cow was confirmed positive during routine slaughter inspection, the herd went on a “test and removal plan.” Rather than depopulating an entire herd outright, California has favored this test-and-removal approach: infected and exposed animals are identified and removed in stages while the rest of the herd continues under movement restrictions and repeat testing.
Quarantine release is only the first milestone, not the end of the state’s obligations. After the release of the affected Tulare County dairy herd from quarantine in July 2014, California entered its 24-month countdown to reapply for “TB-Free” status. That waiting period exists because USDA needs a sustained track record of clean surveillance data before restoring a higher classification tier — a single clean test is not enough.
The state’s broader biosecurity commitments run in parallel with individual herd cases. CDFA’s objectives for the bovine tuberculosis program are to minimize risks to public health, work in partnership with USDA and industry to fully recognize disease control roles and responsibilities, and use sound independent science to guide disease surveillance and control strategies. That partnership model is why quarantine terms and herd management plans are usually negotiated between the producer, CDFA, and USDA rather than imposed unilaterally.
Penalties for Non-Compliance in California
Bovine TB enforcement in California relies primarily on movement and quarantine controls rather than routine fines for ordinary testing lapses. Disease control and eradication measures include quarantines to stop the movement of possibly infected or exposed animals, testing and examination to detect infection, destruction of infected animals to prevent further disease spread, and cleaning and disinfection of contaminated premises. Practically, this means a producer who skips required entry testing risks having animals held at the border, denied a CVI, or placed under quarantine until compliance catches up.
Falsifying test records or moving untested animals in violation of a quarantine order carries more serious consequences, since it undermines a program built entirely on accurate reporting. Accredited veterinarians must mail the signed test sheets to their AHB District Office or email the signed electronic files within 48 hours of reading the test, and gaps or discrepancies in that paperwork trail are typically what trigger CDFA follow-up and, where warranted, referral for further investigation under the state’s animal health statutes.
Important Note: This article summarizes publicly available CDFA and USDA program information and is not a substitute for legal advice. Testing windows, permit requirements, and enforcement procedures can change, so confirm current requirements with your local CDFA Animal Health Branch office or an accredited veterinarian before moving, selling, or importing cattle.
For most producers, the practical takeaway is straightforward: keep testing records current, respect quarantine timelines, and confirm entry requirements before any animal crosses into or out of California. Doing so keeps your herd — and the state’s Accredited Free status — intact.