Texas Animal Health Commission
Box l2966 *Austin, Texas 78711 *(800) 550-8242* FAX (512) 719-0719
Linda Logan, DVM, PhD* Executive Director
For info, contact Carla Everett, information officer, at 1-800-550-8242,
ext. 710, or firstname.lastname@example.org
For Immediate Release--
A beef cattle herd in south Texas has been found to be infected with cattle
tuberculosis (TB), and Texas livestock health officials are seeking the
source of the infection. The disease, caused by Mycobacterium bovis,
can produce internal lesions in animals. Cattle TB can be spread within a herd
when an infected animal coughs, releasing bacteria-laden mucus onto feed
that is consumed, or into the air that is inhaled by nearby cows.
"The investigation began early this summer, when a federal veterinarian,
conducting a routine exam in a slaughter facility, detected lesions in a carcass
that were compatible with those of TB," said Dr. Linda Logan, Texas state
veterinarian and executive director of the Texas Animal Health Commission (TAHC),
the state's livestock health regulatory agency. U.S. Department of Agriculture's
Food Safety and Inspection Services (USDA-FSIS) inspectors are present in all
federally inspected slaughter facilities to examine carcasses for indication of
disease. The inspectors condemn carcasses that
"Tissue samples from the carcass were tested at the National Veterinary Services
Laboratory (NVSL) in Ames, Iowa, where a definitive diagnosis of
cattle TB was made," she said. "We traced the animal back to its original herd in
south Texas. The herd was placed under quarantine, and all of the adult animals
were skin-tested for the disease."
Dr. Dan Baca, the TAHC's TB epidemiologist, explained that, of the 26 animals
tested, 10 had positive results. In late August, the 10 animals were slaughtered,
and the carcasses were examined thoroughly for internal lesions indicative of the
disease. Seven animals had lesions, and tissue samples were collected and
forwarded to NVSL for confirmation tests. The carcasses were incinerated,
preventing their entry into food channels. The remaining 16 animals in the herd
have also been destroyed.
"Fortunately, herds surrounding the infected herd have tested negative," said
Dr. Baca. "The owner of the infected beef herd has been extremely cooperative and
has maintained excellent records of sales and purchases, enabling TAHC
veterinarians to trace animal movement. Our staff has tracked seventy-nine head
of cattle that have been sold out of the infected herd."
As of early September, Dr. Baca said nearly half of the 79 exposed animals have
been slaughtered and examined. One of these animals, a heifer, had lesions that
were indicative of TB. The remaining "traced out" animals also will be
slaughtered and examined. To ensure infection has not been missed, he explained
that herds in which these "traced out" animals have spent time also will also be
"The lesioned heifer (an offspring of the infected cow detected at slaughter) had
been commingled with 208 steers and heifers. These 208 animals, currently under
TAHC quarantine, may be depopulated to avoid any potential disease problems," said
Dr. Baca. "Furthermore, we'll be testing surrounding herds to make sure there
wasn't disease spread. Also, we'll track any movement of animals out of the herd
from the time the lesioned heifer was introduced. The epidemiological
investigation will broaden each time we find a lesioned animal, in order to make
sure we find all potentially infected animals."
"Cattle tuberculosis was a human health threat in the early l900s, when infection
rates among herds was high and before pasteurization--or heat treatment--to kill
bacteria in milk and cheese," said Dr. Terry Conger, TAHC's
Dr. Terry Conger said intensive efforts will be continued to determine the source
of the TB infection in the beef herd. He explained that the rancher had purchased
animals from several herds during the past five years. Three of those source
herds have tested negative. He said the remaining herds will be tested before the
end of September.
"Depopulating an infected herd is the only sure way to eradicate cattle
tuberculosis, a disease that 80 years ago affected nearly five percent of the
nation's cattle herds," said Dr. Conger. "In November 2000, all of the U.S.--with
the exception of Texas' El Paso and Hudspeth Counties, and the state of
Michigan--was recognized by the USDA as tuberculosis-free. If we find that the TB
infection has not spread beyond the animals we are tracing from the infected herd,
the USDA may allow Texas to maintain its accredited-free TB designation."
He said the U.S. Department of Agriculture's Animal and Plant Health
Inspection Services, Veterinary Services (USDA-APHIS-VS) has agreed to provide
indemnity--or purchase funds--for depopulating animals involved in this TB case,
including the 79 head of cattle that had been moved out of the infected herd prior
to disclosure of infection.
Keeping a TB-free designation is particularly important for Texas, because it
allows ranchers to move cattle across state lines without having them tested for
tuberculosis. Dr. Conger said testing can be inconvenient and costly, because it
requires that animals be held for 72 hours from the time an accredited
veterinarian injects tuberculin into the skin under the animal's tail until the
site is examined for swelling that indicates the animal has had exposure to the TB
bacteria. A slaughter examination, followed up with bacterial culture and tissues
tests, are necessary to confirm infection in animals that react to the skin test.
In the "restricted zone" of El Paso and Hudspeth Counties, ongoing low levels of
TB infection in 10 dairies along the Rio Grande have been detected during the past
15 years. Despite periodic testing and the slaughter of infected animals, all
herds in that region have not remained free of disease for more than a few years
at a time, commented Dr. Conger.
Currently, one dairy is under TB quarantine in this zone. Nearly $43 million in
federal funds have been appropriated to buy out the dairies, and the Texas
Department of Health, by a mew state law, will not issue new dairy permits in this
TB restricted zone. Because they originate in a high-risk area for TB, beef and
dairy animals moved from the "restricted zone" into the rest of Texas, or the rest
of the country must comply with strict testing and identification regulations.
Dr. Conger explained that, in Michigan's northeastern quadrant of its lower
peninsula, 17 TB-infected cattle herds have been detected since 1998. Michigan
livestock health authorities believe infected white-tailed deer have spread the
disease to the herds, and have instituted feeding bans to prohibit close
commingling of deer, which can encourage the spread of disease.
"The TAHC staff will be working closely with producers, private veterinary
practitioners and the USDA to finalize the testing of animals moved from the
herd," promised Dr. Logan. "Furthermore, the TAHC staff will continue to
investigate how the herd became infected. Until we have looked into every
possible source, we have not completed our job for Texas producers."