Bovine tuberculosis not completely eradicated
In the early 1900s, bovine tuberculosis was common in cattle herds across the United States. Since then, it has been nearly eradicated, but seems to continue to cause problems at various times.
A recent outbreak of bovine TB in Nebraska has led to the quarantine of 27 herds in 14 north central and eastern Nebraska counties.
One herd in Rock County, Neb., has two sick animals. While the herd has been quarantined, it has not been destroyed. Christin Kamm, spokesperson for the Nebraska Department of Agriculture (NDA), said the herd won't be destroyed unless the owner can be compensated for the loss.
"We appreciate the ongoing cooperation NDA has received from producers with the quarantined herds, as well as the assistance of U.S. Department of Agriculture personnel," said Nebraska Director of Agriculture Greg Ibach. "Through a team effort, we have made huge strides toward addressing this disease situation."
TB is a slow, progressive disease and is difficult to diagnose in the early stages, according to NDA State Veterinarian Dr. Dennis Hughes.
"As the disease progresses, animals can exhibit emaciation, lethargy, weakness, anorexia, low-grade fever, and pneumonia with a chronic, moist cough," he said.
The bacteria can cause the formation of lesions and growths in and on lymph nodes, mammary glands, lungs and other internal organs.
The discovery in the Rock County herd has led to testing of many cattle which may have also come in contact with the infected herd.
"The testing of these animals has and will take a significant amount of time," said Dr. Hughes.
Through the week of July 13, approximately 9,400 head of cattle had been tested for TB, with only the two original animals testing positive.
Kamm said the Caudal Fold Test has been run on these animals and the process of this test is time consuming, as each animal must be run through the chute twice.
"The cattle are injected with a small amount of tuberculin into the web of their tail. Seventy-two hours later the cattle are run through the chute again to check for reaction from the tuberculin," she said.
If an animal experiences a positive reaction to the test, then the animals will be retested using a more definitive blood test. This blood test is called the TB Gamma Interferon test. These samples must be sent to a USDA certified lab for analysis.
"Since these samples must be sent to the USDA lab, it takes a little longer to get the results," said Kamm.
While only two animals have tested positive for TB, 27 herds have been placed under quarantine at the time of writing. This number is down from the high of 43 herds.
Kamm said Rock County, where the infected cows are located, is known to have many Sandhills pastures which producers from other counties will haul their cows to for summer grass.
The movement of cattle in and out of Rock County has led to the quarantines in many of the other counties across Nebraska.
Ibach stressed the importance of keeping records of sales and purchases in order to be able to trace other animals that may have been exposed.
TB is a slow, insidious disease, which can take as little as three to six weeks or as much as a year, after nose-to-nose contact, to be detectable.
"Some of the herds are under quarantine because they may have been in contact with the affected herd, up to as much as four years ago," she said.
Due to the length of time to complete an epidemiological investigation, the USDA has extended the NDA's deadline to test the animals.
Producers owning quarantined herds must first have the permission of the NDA before moving their herds; and these herds may need to be moved to facilitate testing. The herds may also be shipped directly to slaughter in trailers that are sealed by the USDA and NDA.
"Our staff will work with herd owners to ensure that any approved movement of quarantined animals doesn't present the opportunity to expose non-quarantined cattle to the disease," said Kamm.
NDA has asked producers to contact them prior to moving cattle into Rock County for grazing purposes. This is to prevent further spreading of TB. They also encourage producers to talk to other producers who may have cattle in pastures adjacent to their own.
Good biosecurity practices are the best method for prevention of a disease spreading. NDA recommends, when bringing a new animal onto your premises, to keep it in isolation for 60 days. Immediate commingling of animals can lead to fast exposure if the animal is infected.
An additional assurance would be to test the animals prior to introducing them into your herd.
Restriction or elimination of contact with other herds is another method for prevention.
While it is very rare for disease transmission via vehicles, boots or trailers, the NDA recommends restricting on-site visitors, with the exception of regulatory personnel.
Disinfecting footwear and clothing with bleach water is another good disease prevention method.
Human infection with bovine TB is rare today in the U.S. Most human TB cases are caused by a different, yet related, organism.
Pasteurization and meat inspection practices have helped prevent the spread of the organism through milk and meat products.
Eradication efforts in the U.S. began in the early 1900s, which has dramatically reduced the incident of disease.
Several states have had recent outbreaks of the disease. Nebraska, Texas, California, Michigan, New Mexico and Minnesota have had recent cases. States surrounding these have also been on alert for TB.
When TB-free status is lost, breeding cattle and bison moving out of a state need a negative TB test within 60 days prior to shipment, or animals must originate from a herd that has accredited TB-free status, achieved through a formal testing and retesting program.
"It is important to remember that, at this time, only one herd has had animals test positive for TB," said Ibach. "We ask for continued patience, communication and cooperation."
Helping the producer
The economic impact on the affected Rock County, Neb., producer has the potential to be devastating. Nebraska political officials are working toward helping this producer.
All five members of the Nebraska congressional delegation wrote a letter to the USDA requesting that indemnity funds be made available for depopulation of herds infected with TB.
Because Nebraska law prohibits the state from paying indemnity for any animal destroyed as a result of being infected with bovine TB, federal assistance is the sole source of livestock indemnity funding.
Depopulation of the herd, according to Ibach, is not only a step to control the disease, but also important for maintaining confidence in the health of the region's cattle herd.
A July 16 letter from the USDA stated an extension has been granted for more epidemiological work to be done before a disease status determination will be made for the state.
If Nebraska would lose the TB-free status, producers would have to test their cattle prior to shipment to other states.
The USDA also stated in the letter that a final decision on the infected herd plan would not be made until more of the epidemiological investigation has been completed.
Editor's note: For the latest information, visit www.agr.ne.gov or call 402-471-2351.
Jennifer Bremer can be reached by phone at 515-833-2120, or by e-mail at email@example.com.