Bovine Tuberculosis Testing Requirements in Delaware: What Cattle Owners Must Know

Bovine tuberculosis testing requirements in Delaware rarely come up in daily farm life because the state has held disease-free status for decades, but that low profile can lull cattle owners into skipping paperwork they still legally need. A single caudal fold test result, an interstate sale, or an exhibition entry form can trigger federal and state testing rules that catch owners off guard.

This breakdown covers what triggers testing in Delaware, which animals are covered, the approved test methods accredited veterinarians use, and what happens if a test comes back suspect or positive. It also covers quarantine procedures and the penalties tied to skipping required documentation.

What Is Bovine Tuberculosis and Why It Is Regulated in Delaware

Bovine tuberculosis is caused by Mycobacterium bovis, a slow-growing bacterium that produces a chronic, debilitating disease in cattle and can occasionally progress to an acute, rapidly worsening illness. Bovine tuberculosis is a contagious, infectious, communicable disease of animals and humans caused by Mycobacterium bovis, and it is commonly a chronic, debilitating disease that occasionally may assume an acute, rapidly progressive course, spread by direct contact, inhalation of droplets, and ingestion of contaminated feed or milk. That transmission route is precisely why Delaware regulators treat it as a reportable disease rather than a routine health concern.

The disease is also zoonotic, meaning it can pass to people, most commonly through unpasteurized dairy products or close contact with infected animals. There is a zoonotic risk for individuals consuming raw milk and raw milk products from TB-infected animals, and infection with bovine TB compromises the health and reduces production in affected cattle, with the presence of bovine TB potentially resulting in trade restrictions. Nationally, the disease is now uncommon: the prevalence of tuberculosis in cattle, bison, and captive cervids is extremely low in the United States, with an estimated prevalence of 7 per 1 million cattle screened.

That rarity is the result of a long-running federal-state partnership. In 1917, the U.S. Bureau of Animal Industry began the National Tuberculosis Eradication Program, and APHIS and State animal health agencies have collaborated with U.S. livestock producers to administer the program, which has nearly eradicated tuberculosis from the Nation’s livestock population since its inception. Delaware’s testing rules exist to keep that progress from unraveling, and they tie into the same federal framework covered in our overview of common bovine diseases affecting U.S. herds. Bovine TB is also distinct from avian tuberculosis, a related but separate mycobacterial disease that mainly affects birds rather than cattle.

Delaware’s TB Classification Status and Risk Zones

USDA does not regulate every state identically. Instead, it sorts states and zones within states into tiers based on how much disease surveillance shows up in the cattle population. The U.S. Department of Agriculture maintains a monitoring system that classifies states based on the presence of bovine TB within a state’s cattle population, with states or zones within states classified in five categories: Accredited Free, Modified Accredited Advanced, Modified Accredited, Accreditation Preparatory and Non-Accredited, based on the number of cases identified through surveillance programs.

To reach the top tier, a state has to demonstrate sustained freedom from the disease, not just a clean snapshot in time. An accredited-free State or zone is defined as one that complies with the Uniform Methods and Rules, has zero percent prevalence of affected cattle and bison herds, and has had no findings of tuberculosis in any cattle or bison in the State or zone for the previous 5 years, with compliance including demonstrating annually that an adequate amount of testing and slaughter surveillance is done to discover any bovine tuberculosis that might be present. Delaware sits among the large majority of states that have achieved and maintained this Accredited-Free designation, which keeps routine whole-herd testing off the table for most producers.

Important Note: Accredited-Free status is not permanent. If an affected herd is detected in an accredited-free State and the herd is depopulated with an epidemiologic investigation completed within 90 days showing no spread, the State may retain its status, but if two or more affected herds are detected within a 48-month period, the State is reclassified as modified accredited advanced. A single confirmed case can tighten testing rules statewide.

Delaware’s own animal health authority backs this classification with direct state oversight. If there is a serious disease in another state or section of the country, the State Veterinarian may place importation restrictions or an embargo on the affected species to prevent the introduction of the disease into Delaware, and the Poultry and Animal Health Section is charged with preventing the introduction and spread of contagious and infectious diseases into and within the animal population of the state. Delaware’s own administrative code governing the admission of animals lays out the specific entry conditions that apply on top of the federal classification.

Who Must Test and Which Animals Are Covered in Delaware

Testing obligations fall on anyone who owns, sells, exhibits, or moves cattle or bison, working through an accredited veterinarian who handles the actual injection and reading. Federal rulemaking has steadily widened the net beyond cattle alone. USDA has proposed amending the regulations to specify that they apply to goats as well as to cattle, bison, and captive cervids, and to increase the amount of testing required before certain cattle, bison, and goats may be moved interstate.

In practice, most Delaware herds only encounter mandatory testing in a handful of situations rather than on a fixed annual schedule:

• Before interstate movement, when the destination state or federal rule requires a current test result
• During herd accreditation or reaccreditation testing for producers seeking accredited-herd status
• As part of a disease investigation triggered by a suspect slaughter finding or trace-back
• Prior to exhibition, sale through certain markets, or participation in shows that require a Certificate of Veterinary Inspection

Slaughter inspection does most of the heavy lifting for ongoing surveillance. The primary source of tuberculosis surveillance is carcass inspection at all Federal and State inspected slaughter establishments, with the other main sources being testing animals before interstate movement and during disease investigations; live animal testing is performed with a screening test, and if positive, the regulatory veterinarian conducts a confirmatory test. That means an individual cow may never see a tuberculin needle unless it is being shipped, shown, or flagged through one of these pathways. Owners who also keep horses on the same property should note that Delaware applies a comparable movement-testing logic to EIA Coggins testing requirements, and that rabies control follows its own separate schedule under Delaware’s rabies vaccination rules.

Wildlife matters here too, since free-ranging deer can serve as a disease reservoir in some states. Hunters and landowners tracking Delaware’s hunting license requirements should know that captive cervid herds are held to a parallel, though separately administered, TB testing structure.

Approved TB Testing Methods in Delaware

Only a small set of tests count as official under the National TB Eradication Program, and only tuberculin licensed for this purpose may be used. Only bovine purified protein derivative tuberculin (PPD bovis) licensed by USDA may be used for official testing. The screening test almost always comes first, with confirmatory testing reserved for animals that react.

Test	Purpose	Species Approved	Key Detail
Caudal Fold Test (CFT)	Primary screening test	Cattle, bison	Intradermal tail-fold injection; read at 72 hours
Comparative Cervical Test (CCT)	Confirmatory follow-up for CFT suspects	Cattle, bison	Compares bovine and avian PPD reactions in the neck
Gamma Interferon Assay (BOVIGAM)	Blood-based confirmatory alternative	Cattle only	Sample must be drawn within 30 days of the CFT injection
Stat-Pak / DPP Serologic Test	Screening and confirmatory testing in captive cervids	Elk, red deer, white-tailed deer, fallow deer, reindeer	Requires a Designated Accredited Veterinarian

The caudal fold test relies on a visible skin reaction rather than a lab result, which is why physical palpation matters. Test observation without palpation is unacceptable; a negative result is entered when no change is observed at the injection site, and a suspect result is entered when any increase in caudal fold thickness, size, or sensitivity is observed or palpated. Timing of the reaction is fairly predictable: if an animal is exposed to the antigens present in bovine TB, a tuberculin injection results in a delayed hypersensitivity reaction manifested by swelling and induration, with a positive response usually beginning within 8 to 12 hours and peaking about 72 hours after injection.

When a CFT comes back suspect, the clock starts on confirmatory testing. Follow-up CCT testing must be performed within 10 days of the initial caudal-fold injection, or the herd owner must wait 60 days after the injection before a follow-up CCT can be administered, and if the gamma interferon test is used instead, the blood must be drawn within 30 days of the CFT injection, though gamma interferon is not approved for use in bison or captive cervidae.

Pro Tip: Schedule TB testing well ahead of any planned sale, show, or interstate shipment. Results and any required confirmatory testing can take several days to finalize, and a suspect reading forces a mandatory waiting period before follow-up testing can even begin.

Interstate and Intrastate Movement Testing Requirements in Delaware

Interstate movement is where most Delaware producers actually encounter TB paperwork, since the Certificate of Veterinary Inspection is the document that carries test results along with the animal. A certificate of veterinary inspection is an official document issued by a federal, state, tribal, or accredited veterinarian certifying that the animals identified on the document have been inspected and were found to satisfy the regulations pertaining to their intended movement.

Because Delaware and most other states hold Accredited-Free status, cattle moving between them generally avoid extra TB-specific testing. Cattle or bison that originate in an accredited-free State or zone may be moved interstate without further restriction under the tuberculosis regulations. That single fact is why most Delaware cattle owners never need a fresh TB test just to cross into Maryland, Pennsylvania, or New Jersey. States with lower classifications are held to a stricter retest schedule: tests in those situations must be conducted at 9-15 month intervals.

Delaware’s own admission rules layer on top of the federal baseline, and the Poultry and Animal Health Section is the office that fields questions about current entry conditions for livestock coming into the state. Official animal identification also has to travel with the CVI. Feeder cattle and those cattle and bison that move directly to slaughter do not require individual official identification and may move on backtags, but with some exemptions, animals must otherwise be individually identified and accompanied by a Certificate of Veterinary Inspection or other document.

Common Mistake: Booking the veterinary exam too close to a transport date. The most common mistake is scheduling the veterinary exam too close to the transport date, since if testing is required, results can take 3 to 10 business days, and a positive or inconclusive result may require a retest that delays transport by weeks.

What Happens When a Suspect or Positive Result Occurs in Delaware

A suspect reaction on a caudal fold test does not automatically mean an animal has bovine TB, but it does trigger a mandatory reporting and follow-up sequence. Accredited veterinarians must immediately report every suspected or diagnosed bovine TB case promptly to both the Assistant District Director and the State Animal Health Official, and if the test produces any type of response, the veterinarian must immediately notify the APHIS Veterinary Services Area Office and state animal health officials.

From there, only specially trained veterinarians can proceed with confirmatory testing. Only Federal or State regulatory veterinarians who have had specialized training may conduct the follow-up testing, and if the CCT or gamma interferon test indicates that the animal is a reactor, all further herd testing is conducted by Federal or State regulatory veterinarians. A confirmed reactor moves toward slaughter for definitive diagnosis. Following the comparative cervical test, if the test is positive, the animal is slaughtered and tissues are collected for culture of the organism and histopathology.

The reactor animal itself has to be permanently and visibly identified before it leaves the property. Reactor cattle and bison are identified by branding the letter T on the left hip near the tailhead, and by tagging with an approved metal eartag bearing a serial number and inscription U.S. Reactor or a similar State reactor tag, after which such reactors may be shipped to slaughter under permit.

Quarantine and Herd Depopulation Rules in Delaware

Once a herd is confirmed affected, Delaware’s State Veterinarian has direct legal authority to act. When serious, highly contagious diseases are diagnosed, the State Veterinarian, through the authority of the Secretary of Agriculture, may quarantine the animal, herd, or flock to prevent the spread of disease to other premises. From that point, the response generally follows a set sequence:

1. Confirmatory diagnosis through CCT, gamma interferon, or slaughter culture and histopathology
2. Immediate quarantine of the affected premises by the State Veterinarian
3. Epidemiologic investigation, including tracing of animals moved on or off the property
4. A decision between whole-herd depopulation or a test-and-removal plan, depending on herd size and exposure
5. Testing of any herds within the surrounding area, and restocking only after herd-test requirements are met

Officials choose between two management paths once TB is confirmed in a herd. When health officials find tuberculosis in a herd, it is managed by either depopulating the herd or by testing and removing reactor animals, since tuberculosis is not treated in livestock. Surrounding herds get pulled into the response too: all livestock herds within a 10-mile radius will be tested within 6 months of any diagnosis of bovine tuberculosis.

Even after depopulation, restocking a former reactor premises comes with strings attached. If any livestock other than captive cervids are included in a newly assembled herd on a premises where a tuberculous herd has been depopulated, the State or zone must apply the herd test requirements contained in the Uniform Methods and Rules to that new herd. Milk from an affected herd carries its own handling rule during the process: all milk from affected herds must be pasteurized prior to human or animal consumption, and milk from TB reactors must not be used for human or animal consumption at all.

Penalties for Non-Compliance in Delaware

Skipping required testing or movement documentation carries real consequences, both for producers and for the veterinarians who sign off on paperwork. On the veterinary side, sloppy certificate work is treated as a compliance issue in its own right. The most common veterinary accreditation violations include the improper completion and issuance of Certificates of Veterinary Inspection for interstate movement, and compliance action resulting from improper certificate completion can affect a practitioner’s accreditation status.

For owners, the practical fallout of moving animals without proper testing and documentation is fines, holds, and lost transactions. Non-compliance can mean fines, confiscation, or loss of selling privileges, and failing to obtain required documentation can result in fines, quarantine of the animals, and in some cases criminal charges. Border and inspection stops can also halt a shipment mid-transport. If everything is in order, transport is cleared to continue, but if documentation is missing or incorrect, animals may be held until proper paperwork is obtained, at the owner’s expense.

Important Note: This article summarizes general federal and Delaware regulatory concepts and is not legal advice. Testing intervals, forms, and penalty enforcement can change, so confirm current requirements with the Delaware Department of Agriculture’s Poultry and Animal Health Section or your accredited veterinarian before moving, selling, or exhibiting cattle.

Because state entry requirements can shift with disease conditions elsewhere in the country, always check current rules before a move rather than relying on last year’s paperwork. Delaware’s Accredited-Free status keeps the compliance burden light for most producers, but the moment an animal is sold, shown, or shipped across state lines, the underlying federal and state testing framework still applies in full.