Lynn Brezosky, San Antonio Express-News
And forwarded along Texas A&M AgriLife Extension communications by Dr. Sonia Swiger, Texas Animal IPM Specialist.
The
dreaded cattle fever tick, carrier of a blood disease that once nearly wiped
out the U.S. cattle herd, has landed farther north in the Texas interior,
worrying state and federal inspectors that the once-eradicated pest is no
longer under control.
Texas
animal health inspectors recently found new fever ticks Nov. 30 on
a bull on a Live Oak County farm, about 110 miles north from the Mexico border
where they were thought to have been permanently quarantined. Since then, the
ticks have been found on seven neighboring premises, prompting the Texas Animal
Health Commission to set up a temporary "Control Purpose Quarantine
Area." It's the fourth such quarantine zone, following ones set up in
Willacy, Kleberg and Jim Wells counties.
There
are more than 450,000 acres in Texas under various types of fever tick
quarantines that have been set outside of the permanent quarantine zone since
the ticks started showing up farther inside U.S. territory in 2014. The most
recent quarantine zone has grown by nearly 45,000 acres in the past six weeks
as more fever ticks have been found, and now covers 57,541 acres.
Inspectors
are using genetic tests and epidemiological investigations to try to pinpoint
how the ticks ended up in Live Oak - from transporting animals from quarantine
areas near the border or from wildlife such as white-tailed deer and nilgai
antelope carrying them farther into Texas. The latter is the biggest concern,
indicating that previously successful efforts to contain the ticks to the
border region are failing.
The
ticks are carriers for bovine babesiosis, a blood disease that in the 1800s
wiped out much of the U.S. cattle herd and caused Kansas and other states to
shun or restrict cattle from Texas.
In 1943,
the ticks were declared eradicated from the U.S. save for a permanent quarantine
zone along the Rio Grande established to control ticks that find their way
across the river from Mexico. But during the past few years, the ticks have
increasingly been found outside that zone, prompting expanded quarantine zones
in border counties and temporary quarantine zones in three counties farther
north.
"I
don't want to jump to conclusions," Schwartz said of the possibility the
ticks are migrating north on the backs of wildlife such as nilgai, a non-native
antelope that's become a nuisance carrier of the tick. "The concerning
thing is we haven't determined the source of those ticks yet."
While
cattle owners in quarantine areas are required to round up, inspect and treat
cattle for ticks, the Live Oak County discovery was unexpected. A veterinarian
called to examine the sickly bull called a state livestock inspector to check
some of the ticks he found on the animal's skin.
"That
day she tentatively identified those as fever ticks, that's the day we sprang
into action there," Schwartz said of the inspector.
The bull
likely was anemic from all the ticks drawing his blood, Schwartz said, but did
not suffer from babesiosis.
While
babesiosis is still an issue for cattle south of the border, it has not shown
up in U.S. cattle for decades, he said.
"I
think it's a tribute to the success of the program to have kept the fever
ticks, the hot fever ticks with babesiois, out of the country," Schwartz
said. "We've had some fever tick incursions, but none of them have been
carrying babebiosis."
As in
other quarantine zones, cattle in the Live Oak area must be "dipped"
in a treatment solution every 10 to 14 days or injected with a vaccine every 25
to 28 days, which in either case usually involves costly helicopter roundups
that are stressful to cattle. Hunters also are required to call inspectors to
check any harvested deer for the ticks.
Once
hunting season is over, state and federal officials also plan to set up feeders
full of deer corn treated with a poison that kills the ticks and is aimed at
preventing them from spreading from the infested ranches. Nilgai, which aren't
native to the U.S., have become particularly worrisome in South Texas as they
travel long distances and can easily jump fences, but they are not believed to
have strayed as far north as Live Oak County.
Ron
Gill, head cattle extension specialist at Texas A&M University, said the
Live Oak County discovery worried ranchers who thought that as long as they
followed protocol the fever tick wouldn't spread.
"It
periodically jumps out of the quarantine zone but not that far out," he
said. "Normally it will be one of the adjacent counties and they'll fight
it back into the quarantine zone. So I think the thing that's got everybody
more vocal about it now is it jumped a little further than usual."
Coleman
Locke, who runs cattle in affected areas in Kleberg and Willacy counties, fears
the tick could once again threaten the entire Texas cattle industry.
"It
concerns me as a cattleman," he said. "We've got to get it under
control. … A lot of Texas cattle go to feed yards in Kansas and Nebraska to
feed out. We need our Texas cattle to be able to go anywhere."
Thanks Dr. Swiger!
Blayne
