What is Bovine Tuberculosis?
Bovine tuberculosis (TB) is a disease caused by the bacterium Mycobacterium bovis. The disease is found primarily in cattle, but has also been found in captive cervidae (deer and elk), bison, goats, and carnivores such as coyotes. It can affect any warm-blooded animal, including humans.

Symptoms of Bovine TB
Animals infected with bovine TB may not show any outward signs of illness, but may eventually exhibit weight loss and a gradual decline in general health. TB lesions may be found in any organ or body cavity of diseased animals. Because the lungs are usually affected, the animal may display symptoms such as coughing and difficulty breathing.

How Bovine TB is Spread
Bovine tuberculosis is most commonly spread through respiration. Invisible droplets (aerosols) containing TB bacteria may be exhaled or coughed out by infected animals and then inhaled by other animals or humans. Animals who come in close contact with infected wild deer, or those kept in close contact with other infected animals in enclosed areas like barns, are at greatest risk for exposure to bovine TB. Livestock may also be infected by ingesting water or feed that has been contaminated with saliva and other discharges from other infected animals. Animals and humans may contract bovine TB when they drink unpasteurized milk from infected cows or consume raw or undercooked meat from infected animals.

Why Testing is Crucial
Bovine TB is not a new problem in Michigan. Bovine TB was frequently found in dairy and beef cattle in Michigan, and many other states, through the mid 20th century. In fact, Michigan was not declared free of bovine TB in cattle and bison until 1979. However, bovine TB has been an historically rare disease in wild deer. Prior to 1994, only eight wild white-tailed or mule deer had been reported with bovine TB in North America.

According to the USDA, at the beginning of the last century, bovine TB caused more losses of livestock than all other livestock diseases combined.

This prompted the establishment of the National Cooperative State/Federal Bovine Tuberculosis Eradication Program for bovine TB in livestock.

In 1975 and again in 1994, bovine TB was discovered in one wild white-tailed deer in the northeast corner of Michigan's Lower Peninsula. State scientists recognized the need to be proactive in monitoring this disease, and decided to test cattle and deer in the areas where the infected deer were found. Michigan is thought to be the only place on the continent where the disease has become established in the wild deer population.

As a result of testing, in June 1998, bovine TB was confirmed in a beef cow in Alpena County. Since that time the disease has been confirmed in multiple cattle herds in Michigan. Bovine TB has also been detected in numerous captive and wild deer as well as wild carnivores such as coyote and bobcat, and in one case a domestic outdoor cat.

In an intensive effort to eradicate bovine TB in livestock, the Michigan Department of Agriculture (MDA), working with the U.S. Department of Agriculture, Michigan State University and private veterinarians, has launched a statewide livestock testing program.

Why is TB eradication necessary?
The eradication of bovine TB is necessary for a variety of reasons including the reputation of Michigan's quality agricultural products and the health of our natural resources. Michigan is now one of two states in the US that still has bovine TB, and the only state where the disease has become established in wild deer. At the national level, the USDA has lowered our status to nonmodified accredited, until we can prove that we no longer have bovine TB in the cattle herds of Michigan. And, until TB is eradicated, other states will continue to impose strict importation requirements that protect their livestock.

MDA plans to test all cattle, goats, captive cervidae and bison herds in Michigan at least once by December 31, 2003. Simultaneously, the Michigan Department of Natural Resources has expanded its testing and surveillance efforts in Michigan's wildlife population. The Michigan Department of Community Health also offers TB testing for people concerned about possible exposure to the disease.

With the combined efforts of the three State Departments, and with help from MSU and the USDA the eradication of bovine TB in Michigan will be successful. Historically bovine TB was found in every state of the nation. In 1917 the USDA began an intensive and aggressive campaign to eradicate TB in livestock. The success of the USDA eradication program has led to Michigan's adoption of the same model.

Who Does the TB Testing in Livestock?
Animals are tested by state or federal veterinarians, or, at a herd owner's request, the caudal fold tuberculin testing can be done by any private veterinarian. If a private veterinarian does the testing, the state will pay for the whole herd bovine TB test, as long as the veterinarian has completed a certified training course offered by MDA, and arrangements are made with MDA in advance.

On the prescheduled testing day, the producer should corral the herd before the veterinarian arrives on the farm. Dairy cattle are often tested in the milking or stanchion barn, but the veterinarian must have free access to the animal's head and tail for testing and identification purposes. Farmers should work with the veterinarian to confine livestock in existing handling facilities or in handling equipment brought by the veterinarian, so that the livestock will remain calm and can be securely restrained before the test is administered. Although gathering and handling the livestock may cause some excitement for the animals, be assured your stock will be carefully handled to avoid undue stress.

What to Expect on Testing Day
Step-By-Step Testing Procedures
Phase I
On-farm Caudal Fold Tuberculin Test

1. The Caudal Fold Tuberculin Test (CFT test) is the first screening step in the TB-testing process. MDA will contact livestock producers to schedule a testing appointment. Producers may also call MDA to request an appointment.
2. At the prescheduled testing day and time, the veterinarian arrives at the farm, and assesses the available on-farm handling equipment. The veterinarian will either use the on-farm equipment or set up additional equipment. The animals are then moved into handling equipment for testing.
3. Once the animal is secured, the CFT test is administered.

   The Purified Protein Derivative (PPD) tuberculin is injected intradermally (between the layers of the skin) of the caudal tail fold, under the animal's tail. Some veterinarians will make a mark on the animal's hide to indicate which side of the caudal tail fold was injected. The animal is also given a unique, permanent identification number, usually an ear tag (if a permanent ID number is not already present). The tag number, sex and approximate age of the animal is recorded by the veterinarian or an assistant. However, if the animal is individually registered, with a registration number tattoo that corresponds with the registration papers, that tattoo may be used as official identification.

4. The animal is then released from the handling equipment, but should remain easily accessible until the injection site is examined 72 hours later, plus or minus six hours. When each animal in the herd has been injected, the injection portion of the test is complete.
5. The same veterinarian who injected the caudal fold tuberculin must examine the injection site, and the examination must take place 72 hours, plus or minus six hours after the injection. Timing of the injection site examination is very important for an accurate reading. When the veterinarian arrives, each animal is individually restrained for observation by the veterinarian. The veterinarian or an assistant records the tag number and test results. The veterinarian will feel and observe the injection site.
6. In the majority of cases, no response is observed and this is the end of testing for that animal. Even if there is a response to the CFT test, try not to be alarmed. Five to seven percent of the cattle, goat and bison population will respond to the CFT test. This may happen because the animal may have been exposed to another disease that causes a response (e.g., Mycobacterium avium [Bird TB], or paratuberculosis [Johne's Disease]). The animal's condition cannot be accurately determined by observation alone.
7. If there is any response at the injection site (swelling, redness, hardness, etc.) the animal is considered suspect, and further testing is required. The herd is quarantined if even one animal is suspect. This means no animals can come into the herd and no animals can move out of the herd, without approval from MDA.

1. The Comparative Cervical Tuberculin Test (CCT test) is the next step in the bovine TB-testing process. This test is done only on animals that respond to the CFT, if your private veterinarian conducted the CFT test be sure your veterinarian contacts MDA immediately. The CCT test must be done within 10 days of the injection date of the CFT (one week after the reading of the CFT), and must be administered by a state or federal veterinarian. If for some reason the test is not done within 10 days, then the herd remains quarantined and the test is re-administered after 60 days. The MDA will contact the herd owner to schedule a CCT testing appointment for animals that responded to the CFT test as soon as your private veterinarian notifies the department.
2. At the prescheduled testing day and time, the veterinarian arrives at the farm. The veterinarian will either use the on-farm equipment or set up additional equipment. The animals are then moved into handling equipment for testing.
3. Once the animal is secured, a section of the neck is shaved in two places before administering the CCT test between the skin layers (intradermally) on the animal's neck (cervical region). Skin thickness is measured using a special caliper and then the veterinarian will inject avian (bird) tuberculin and bovine (cattle) tuberculin into two shaved sites on the neck.
4. The animal is then released from the handling equipment, but should remain easily accessible until the injection sites are examined three days later. When each animal that responded to the Caudal Fold Test (Phase I) has been injected with tuberculin in the neck area, the injection phase of the CCT test is complete.
5. The same veterinarian who administered the CCT test must examine the injection sites, and the examination must take place approximately 72 hours (three days) plus or minus six hours, after the injection. Timing of the injection site examination is very important for an accurate reading. When the veterinarian arrives, each animal is individually restrained for observation by the veterinarian. When observing the avian and bovine tuberculin injection sites, the veterinarian looks for differences in the two sites, and measures the skin thickness with a special caliper. Do not be alarmed by the swelling. Quite often the reaction is to the avian TB injection. The veterinarian or an assistant records the tag number and test results.
6. Based on observation, touch, measurement and comparison of the two injection sites, test results for each animal are plotted on the official USDA CCT scattergram. Based on where the results fit on the graph, the animals will be classified as negative, suspect or reactor. Each classification has significant meaning:
   • Negative: Animals classified as negative on the CCT test are considered TB negative. If the entire herd tests negative, the quarantine is released.
   • Suspect: An animal whose response to the CCT test is plotted midway on the graph is classified as a suspect. The herd owner must decide whether to have the suspect animal removed from the herd at that time for euthanasia and testing at MSU, or to have the animal re-tested on the farm after 60 days. (The 60-day waiting period is necessary for accurate results, because the initial TB test may cause a false response if the animal is tested in less than 60 days.) If the animal is removed for necropsy and further laboratory tests, the herd owner will receive payment for the animal based on the value of the animal as written in PA 466 of 1988, the Animal Industry Act. Shipping costs will also be paid by MDA. The herd will remain under quarantine until at least initial laboratory test results are available. If the herd owner opts for a 60-day retest, the herd will remain under quarantine until the second CCT test results are available. Any animal that responds as a suspect to two CCT tests is reclassified as a reactor, and arrangements for removal from the farm are made, with indemnification and shipping paid by MDA. Classification as a suspect does not mean the animal has bovine TB. Bovine TB can only be verified by several laboratory tests after euthanasia.
   • Reactor: An animal is classified as a reactor if its response to the CCT test falls into the reactor range on the official USDA CCT scattergram. An animal canalso be classified as a reactor if it plots as a suspect on the graph on two separate CCT tests. Classification as a reactor at this point does not mean the animal has bovine TB. Bovine TB can only be verified by laboratory tests after euthanasia. Arrangements will be made for reactor animals to be removed from the farm for necropsy and further laboratory tests, and the herd remains quarantined until the laboratory test results are available. If laboratory results upon euthanasia and necropsy show definitive signs of bovine TB, the animal is classified (or in some cases, reclassified) as a reactor. Animals responding to the CFT test that were found negative or suspect to the CCT test may be reclassified as reactors when included in a herd test that results in the confirmation of bovine tuberculosis in the herd, or if the designated tuberculosis epidemiologist determines that the reactor classification is justified. Milk from reactor animals cannot be put into the milk bulk tank or consumed by humans or animals. Livestock producers are advised to keep reactor animals confined and separated from the rest of the herd until they can be removed from the farm, purchased by MDA and brought to MSU for testing.

For more information about animal purchase prices, please refer to the Indemnification definition in the back of the book.

Phase III
Re-testing Suspect Animals
Animals classified as bovine TB suspect by the CCT test are re-tested with the CCT test at least 60 days after the first CCT test injection. Animals classified as suspect on a second CCT test are automatically reclassified as reactors and subject to the rules and regulations governing this classification.

Phase IV
Necropsy and Laboratory Testing
When animals are removed from the farm for further testing, they first go to the Animal Health Diagnostic Laboratory at Michigan State University for necropsy and histopathology. Scientists look for signs of internal lesions, swollen lymph nodes and other signs of disease. Tissue samples are collected and forwarded to the Laboratory for culturing and further diagnostic testing. (Please refer to the definition section of this brochure for detailed descriptions of the laboratory tests.)

What Are the Herd Owner's Choices?
As outlined in the testing procedures, the herd owner has the choice of who will conduct the CFT test. A herd owner may choose to use a private veterinarian instead of a state or federal veterinarian. As long as the private veterinarian has taken the certified training class offered by MDA, and arrangements are made with MDA in advance, MDA will pay for the first CFT test for the entire herd. A herd owner also has two options if an animal is classified as a CCT suspect during testing. These options are outlined in Phase II, Number 6, part B.

MDA does not pay for any second test requirements imposed by other states for out-of-state shipping.

When a farm owner is notified that the CCT reactor did indeed have bovine TB the owner may choose one of two options; either complete herd depopulation, or the test and removal option.

Under a test and removal program for a bovine TB infected herd, the farm remains under quarantine for an extended period of time until all testing reveals a bovine TB-negative herd. Each time an animal responds to a CCT test on the farm, it is immediately removed and the testing will commence again from the beginning of the protocol. When a positive animal is found the herd will remain under quarantine and be re-tested no sooner than 60 days after removal of the positive animal. No animals are allowed to leave or enter the farm without prior written permission by MDA. When no positive animals are found on all subsequent testing, the quarantine may be removed from the farm. This process of approximately 6 whole herd tests may take upwards of 24 months providing no additional infected animals are found. Once the quarantine is removed, yearly tests may be required on the herd for 5 years. Dairy herds in the test and remove plan may continue to sell milk while under quarantine, provided all bovine TB reactors are removed from the farm.

Depopulation
Farmers are encouraged to consider whole herd depopulation, since the procedure for testing and removal of the infected animals can be costly and have long term implications for the farm operation. Depopulation defined by the USDA Bovine TB Eradication Uniform Methods and Rules is the destruction of all livestock exposed to bovine tuberculosis in the herd before any restocking of the premises with cattle, captive cervids, bison or goats.

When the owner chooses to depopulate, MDA purchases all livestock from the producer. The livestock are removed from the premises and sent to Michigan State University. The farm is disinfected and may be repopulated as soon as an USDA Designated Tuberculosis Epidemiologist determines that the premises are clean and free of the risk of re-infection or after 1 year from removal of the animals.

After gross necropsy, a series of tests are conducted.

These tests are:

,li>histopathology with acid-fast staining
• the Polymerase Chain Reaction (PCR) test
• bacterial culturing
• DNA strain typing

Caudal Fold Tuberculin (CFT) Test Suspect
Any cattle, bison or goat that shows a response to the caudal-fold tuberculin test.

Comparative Cervical Tuberculin (CCT) Test Negative Animal
Any cattle, bison or goat that is classified as negative after comparison of reactions to biologically balanced bovine PPD tuberculin and avian PPD tuberculin in separate sites in the cervical (neck) area. Classification is based on measurement of the swelling associated with each injection after plotting them on the official USDA CCT scattergram. If plotted in the negative zone, the animal is classified as bovine TB negative. Comparative Cervical Tuberculin (CCT)Test Suspect Animal
Any cattle, bison or goat that is classified as suspect after comparison of reactions to biologically balanced bovine PPD tuberculin and avian PPD tuberculin in separate sites in the cervical (neck) area. Classification is based on measurement of the swelling associated with each injection after plotting them on the official USDA CCT scattergram. If plotted in the suspect zone, the animal is classified as bovine TB suspect. Animals classified as bovine TB suspect by the CCT test can be re-tested by the CCT test at least 60 days after the first CCT test injection or taken and submitted directly to an appropriate diagnostic lab for further testing. Animals classified as suspect on a second CCT test are automatically reclassified as reactors and subject to the rules and regulations governing this classification.

Comparative Cervical Tuberculin (CCT) Test Reactor Animal
Classification is based on measurement of the swelling associated with each injection after plotting them on the official USDA CCT scattergram. If plotted in the reactor zone, the animal is classified as a bovine TB reactor. Animals classified as a suspect on two sequential CCT tests at least 60 days apart are automatically reclassified as a reactor. Animals classified as reactors are subject to the rules and regulations governing this classification. Animals classified as bovine TB reactors are quarantined to the premises until the animal can be removed and sent to the laboratory at MSU.

Culture
The National Veterinary Services Laboratory in Ames, Iowa attempts to grow the bacteria in the laboratory from tissue samples. It may take up to 90 days or longer to get results because tuberculosis bacteria grow slowly. The culture is a useful tool in the diagnostic process. Cultures also provide useful information about the particular strain of TB. Depopulation
The destruction of all livestock in a herd exposed to bovine tuberculosis.

Euthanasia
Bringing about humane death.

Epidemiology
The science that deals with the incidence, distribution and control of disease in a population. An Epidemiologist will consider all of the factors surrounding the presence of bovine TB on a farm including exposure to wildlife, tracing movement of livestock on or off a property and housing conditions.

Exposed Animals
Any livestock that have been exposed to bovine tuberculosis due to interaction with other livestock that had the disease.

Histopathology
Tissues collected during necropsy are prepared in a special solution, sliced thin, and placed on slides. A special stain (acid-fast) is also used on some samples. The tissue slides are examined under the microscope, and studied for signs of disease.

Indemnification
Payment for the purchase of bovine TB infected livestock from the producer, payment is based on the value of the animal as written in PA 466 of 1988, the Animal Industry Act.

Necropsy
The equivalent of an autopsy for humans. The animal's physical condition is considered, including the presence (or absence) of internal lesions, swollen lymph nodes and other signs of disease. Tissue samples are collected, examined and forwarded to the National Veterinary Services Laboratory in Ames, Iowa for further testing.

PPD Tuberculin
Purified Protein Derivative Tuberculin. A product that is approved by, and produced under, USDA license for injection into livestock for the purpose of detecting bovine tuberculosis

PCR Test
The polymerase chain reaction (PCR) test is a DNA-based test used by the National Veterinary Services Laboratory on TB-suspicious tissue samples. A positive PCR test means tuberculosis bacterium are present. This is new technology, similar to DNA tests used in criminal investigations. Acid-fast bacteria must be present on the slide before a PCR test can be run.

Quarantine
Any herd containing an animal classified as a suspect or reactor to any of the tests for bovine tuberculosis shall be quarantined until further testing rules out Mycobacterium bovis. Animals under quarantine are not permitted to leave their premises, and no animals may enter the premises, unless a state or federal permit has been obtained.

Strain Typing
If M. bovis is grown on a culture its DNA make-up is determined by genetically fingerprinting the strain of organism. All of the animals in Michigan thus far have the same M. bovis strain of infection.

A Commitment to Safety
The Bovine TB Eradication Project maintains a strong commitment to eradicating bovine TB from Michigan livestock and deer. In keeping with its long-standing tradition of making food safety a top priority, MDA pledges an equally rigorous effort to continue ensuring the safety of both venison and beef meats, and milk, through comprehensive testing, monitoring and educational efforts from the farm or processing plant to the retail store.

Contact Information :
Michgan Department of Agriculture
Animal Health Liaison
(517) 241-4339

Michgan Department of Community Health
Communicable Diseases
(517) 335-8165

Michigan Department of Natural Resources
Rose Lake Wildlife Research Station
(517) 373-9358

MSU
Contact your local county extension agent or ANR Communications
(517) 432-1555