Horse Health
A few miles north of the Rio Grande, where spring temperatures climb past
100 degrees, helicopters work in concert with cowboys to gather cattle,
thorny bushes nick kneecaps, and dust and manure swirl up noses and down
collars, and cowboys inspecting, dipping or treating cattle are gritty and
soaked with sweat before noon.
For a small contingency of government “hands” and livestock producers on
the border, the very presence or absence of ticks on cow bellies or deer
flanks indicate defeat or victory in the fight against the fever tick, a
foreign-origin pest that threatens the health of U.S. cattle.
This is the scene that Mr. Bruce Knight, USDA’s undersecretary of
agriculture for marketing and regulatory programs, traveled to South Texas
to see in mid-March to gain a first-hand perspective of the fever tick
situation. He visited a fever tick-infested premises, observed gathering
and treatment of cattle, and discussed fever tick issues with ranchers,
USDA and TAHC staff. Mr. Knight noted the time, work and expense endured by
cattlemen to round up cattle and present them for treatment. He also
experienced the difficulty in gathering cattle in the brush country of
South Texas, where a helicopter is as necessary as cowboys on horseback.
“We are fighting a border war against the fever tick,” said Dr. Bob
Hillman, Texas’ state veterinarian and head of the Texas Animal Health
Commission, the state’s livestock and poultry health regulatory agency. “I
believe Mr. Knight’s visit to the fever tick quarantine area will result in
a commitment and dedication of resources necessary to successfully operate
the fever tick program.”
In 1943, the U.S. pushed the fever tick across the border and has
maintained a permanent quarantine zone along the Rio Grande from Del Rio to
Brownsville, Texas, since that time as a deterrent to re-infestation with
the fever tick. However, the tick was never eradicated from Mexico, which
serves as a continuous source for reintroduction into US cattle herds.
“Last summer the pest gained a foothold beyond the 852-square mile
permanent, USDA-patrolled fever tick quarantine zone,” said Dr. Hillman.
“As of mid-March 2008, we are making progress in fighting the outbreak,
having defined the outer limits of the tick’s spread. Now the TAHC, USDA
and livestock producers are working from the ‘outside in’ to eradicate the
tick, a process that may take another 16 to 18 months, if no additional
infestations are discovered.”
“Due to fever tick infestations, more than 1,000 square miles of ranchland
have been temporarily quarantined since last summer. The quarantines are in
Starr, and Zapata counties, and in a contiguous area of Maverick, Dimmit
and Webb counties,” Dr. Hillman said. “From these areas, no domestic or
exotic livestock capable of hosting the fever tick can be moved without an
inspection, treatment and a permit. These temporary quarantines more than
doubled the geographic scopeto an area larger than Rhode Island and
Washington, D.C.--for which fever tick monitoring, inspection and treatment
must be provided.”
“The battle costs money, but fighting the battle against fever ticks has
been like putting a band aid on a lacerated artery,” said Dr. Hillman.
Beginning in August 2007, the TAHC worked with the U.S. Department of
Agriculture to develop a funding request, which if fulfilled, would be
sufficient to provide the personnel, equipment and supplies required to
contain, and then eradicate the fever tick outbreak from the temporarily
quarantined areas.
On March 19, 2008, USDA announced that $5.2 million, would be made
available to control the outbreaks of fever ticks occurring outside the
permanent quarantine zone between Texas and Mexico. “We are very
appreciative that these funds are being provided to aid in the fight
against the fever tick,” said Dr. Hillman. “They will certainly help in
this battle against a relentless foe. However, this level of funding is
significantly less than the $13 million requested and will be enough to
address only the program’s most dire needs.”
“If we are to be ultimately successful in eliminating fever ticks from the
temporarily quarantined areas, and push the fever ticks past the permanent
quarantine zone and back into Mexico, we must have sustained funding over
many years. The amount provided will be utilized efficiently, but it will
not be sufficient to complete the job,” said Dr. Hillman.
Besides the sheer size of the area under quarantine, nearly 100 premises
(up from 40 premises in 2007) in the permanent and temporarily quarantined
areas are known to have fever ticks. On these pastures, livestock must be
examined and treated every 14 to 28 days, depending on the acaracide
products used. As an alternative, the animals can be “tick-free” for two
consecutive treatments, then transferred under permit from the property,
leaving the pasture vacant for at least nine months, with the idea that the
ticks will starve. Because the fever tick has shown an ability to adapt to
wildlife hosts, pasture vacation may no longer be an effective option for
‘clearing’ a pasture of fever ticks.
Since October 1, 2007 (the start of federal fiscal year 2008) more than 52
fever tick infested premises have been detected in the permanent and
temporary quarantine areas. During the 2007 hunting season, about 2,300
white tail deer and other wildlife hosts harvested in the quarantined areas
were examined for fever ticks by the USDA and TAHC. Inspections disclosed
that, of the 52 newly detected fever tick-infested premises, 23 premises
had fever tick-infested wildlife. Fever ticks were detected on white-tail
deer, fallow deer, axis deer, and red deer. The pests also were found on
aoudad sheep, a species previously not thought to be a fever tick host.
“This is disturbing, but not surprising,” said Dr. Hillman. “Wildlife
host populations are high in these areas. Scientists believe that the fever
tick prefers cattle as a host, but when tick populations are unchecked, or
cattle hosts are not available, the pest will infest wildlife hosts.”
Fever tick-infested wildlife complicates eradication. Treatment for
free-ranging wildlife is limited to feeding ivormectin-treated corn or
drawing animals to ‘four-poster’ stations where they rub against
pyrethrin-treated posts, which transfers the chemical to the head, neck and
ears of animals and kills the ticks. However, some products require a
60-day withdrawal period, so they can’t be used just prior to or during the
hunting season.
One of the most time-consuming and frustrating tasks in the fever tick
fight has been tracing the more than 800 head of cattle moved from the area
since August 2006. TAHC staff spent several months looking for the animals,
due to a scarcity of records and animal identification. Most of the
shipments had moved within Texas, but some animals had been transported as
far away as Kansas, Colorado, Oklahoma and Wyoming. All the animals have
been inspected, and none were infested with the fever ticks.
“The very success of the fever tick program may be its biggest problem. The
USDA’s Fever Tick Force has run for years under-funded, understaffed, but
without a whimper. This small crew has held back the tick onslaught for
years,” said Dr. Hillman.
It is time to remember why this tiny, prolific pest is so deadly to cattle,
he noted. Fever ticks by themselves are a problem. Fever ticks that carry
the blood parasite, “babesia,” are deadly and can infect cattle with
“cattle tick fever,” causing them to suffer bloody urine, diarrhea, fever
and extreme anemia before death.
“We either address the fever tick in south Texas, or we could be addressing
fever ticks in Oklahoma, Missouri, Virginia, California, or a host of other
states where the tick would flourish,” said Dr. Hillman. “Fever ticks are
not just a “Texas” problem. Through extraordinary effort by cattlemen, and
state and federal animal health officials – beginning in 1906 and
culminating in 1943--these pests and babesiosis, the disease they carried,
were eradicated from the United States. These fever ticks are now
classified as foreign pests, and they are a U.S. problem.”
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