Controlling Cattle Fever Ticks
February 2002
Veterinary Services
The rugged cowboys that dominated the American television screen in
the 1950's may have faded away, but real cowboys still ride the rangeómake
that the river banksóof the Rio Grande. These cowboys work for
the U.S. Department of Agriculture's (USDA) Animal and Plant Health
Inspection Service (APHIS) and are looking for the ticks that cause
cattle fever, another term for babesiosis.
Known as "tick riders," these cowboys first appeared in 1906
as part of the Cattle Fever Tick Eradication Program (CFTEP), one of
the first cooperative State?Federal eradication efforts. Through the
CFTEP, the tick riders helped eradicate the existing infestation of
cattle fever ticks in the United States and prevented the introduction
of new cattle fever ticks from Mexico. They did so by using horseback
patrol and systematic quarantines along the Rio Grande River. By 1943,
the tick riders had helped eradicate the two species of cattle fever
ticks from the United States, with the exception of a permanent quarantine
zone between Texas and Mexico.
The ticks of interest to the APHIS tick riders are the cattle fever
tick (Boophilus annulatus) and the southern cattle tick (Boophilus microplus).
These pests are responsible for the spread of a severe and often fatal
disease of cattle, commonly known as Texas or cattle fever. The disease,
spread through a parasite that destroys red blood cells, was eradicated
from the United States by CFTEP between 1906 and 1961.
Background
Spanish colonists first brought both types of cattle fever ticks and
cattle fever disease to the United States through the introduction of
infested cattle. Currently, both types of ticks infest most tropical
and subtropical areas of the Western Hemisphere. They frequently are
found in the part of Texas that borders on infested parts of Mexico
and are occasionally found in California. Florida had outbreaks of cattle
ticks in the 1950's and in 1960.
Clinical Signs
Cattle with the acute form of tick fever (generally contracted during
the summer) develop high temperatures (107% or 108% F) and stand with
their heads lowered and backs arched. They experience a loss of appetite,
constipation followed by diarrhea, and decreased milk production. "Red
water," or bloodstained urine, is common. Death usually comes within
3 or 4 days after fever develops.
Cattle affected with the chronic form of cattle fever (contracted in
late autumn and winter) develop a mild fever and stop eating and chewing
their cuds. They also develop anemia and lose weight rapidly. The chronic
form of the disease lasts for many weeks. Some deaths occur, but most
animals recover gradually.
Surviving animals may display nervousness known as "tick poverty"
or "tick worry"óthey become weak, stunted, and anemic
from the continuous loss of blood. Ticks can reduce the weight of a
1,000–pound steer by 200 pounds in a year. Infected cattle frequently
have relapses 3 to 6 weeks after their temperatures return to normal
and become susceptible to other diseases or secondary infections.
In summer, the incubation period (the time from when an animal becomes
infected until it first shows disease signs) is usually 10 to 15 days
after the infected larvae, or seed ticks, begin feeding on the animal.
In winter, it may take as long as 90 days.
Ticks' Life Cycle
Cattle fever ticks spend the early part of their lives on the ground.
Eventually they infest cattle, or–occasionally–horses, mules,
sheep, goats, or deer. The ticks must have blood from an animal host
to complete their life cycles.
Newly hatched seed ticks, or larvae, are barely visible to the unaided
eye. These waxy brown, six-legged ticks crawl up grass or plants where
they wait for an animal to pass by. If ticks do not find a host, they
eventually die of starvation. In summer, seed ticks may starve after
3 to 4 months; in colder periods, they may survive for 6 months.
Usually seed ticks first attach themselves to soft skin inside the
animal's thigh, flanks, and forelegs or along the belly and brisket.
There, they suck blood, or engorge. Then these ticks molt twice: seed
ticks become tiny, white,eight?legged nymphs; after engorging about
a week, nymphs molt to become adults. Many adult ticks are olive green;
others are mottled yellow or olive brown.
Eradication
Cattle fever has caused enormous losses to the U.S. cattle industry
in the past. Before the nationwide eradication program began in 1906,
direct and indirect economic losses were estimated to be $130.5 million
(which would be approximately $3 billion today). If the ticks had not
been eradicated from the United States, the cattle industryís
losses from ticks could amount to approximately $1 billion annually.
Current Activities
The tick riders, working through CFTEP, still patrol the Rio Grande
river on horseback. The highly successful program currently consists
of 57 inspectors, 7 supervisors, and a director of field operations,
with 2 assistants. The quarantine or "buffer" zone extends
over 900 miles from Del Rio, TX, to the Gulf of Mexico, and is 200 yards
to 6 miles wide. Outbreaks outside the zone are rare. Premises found
to be infested with cattle fever ticks are placed under quarantine for
6 to 9 months, depending on the time of year.
APHIS tick riders detect and apprehend any illegally entered (stray
or smuggled) Mexican livestock or native livestock that have crossed
into Mexico and returned. APHIS officials inspect and dip all native
livestock being moved within or out of the buffer zone in pesticides
that kill ticks without injuring the animals.
Although a single treatment kills all the ticks on an animal, it will
not assure eradication because it does not prevent reinfestation. Only
long-range programs can rid an area of ticks. For this reason, APHIS
dips cattle at regular intervals for at least 1 year following direct
or presumed contact with the pest.
Without these controls, cattle fever ticks would reinfest areas of
the United States that have warm climates.
If Your Cattle Have Ticks
If you suspect that your cattle have cattle fever ticks or you do not
know the species infesting your cattle, ask an APHIS tick inspector
or your local veterinarian to have the ticks identified and give you
information about control or eradication. Each suspect animal should
be chute-restrained so an experienced person can make a dry-scratch
inspection. State and Federal inspectors regularly examine cattle throughout
the infested buffer area until all cattle fever ticks are eradicated.
Chemical dips–when properly used–kill ticks on animals
without injuring the animals. You may obtain the names of the permitted
dips from your veterinarian, State or Federal disease control officials,
or the Federal veterinarian in charge of your State. Every animal in
every infested and exposed herd must be treated.
Getting the Word Out
The ultimate goal of the CFTEP is to completely eliminate cattle fever
ticks from the United States. Success of the program not only prevents
exposure of U.S. livestock to babesiosis but allows the annual importation
of hundreds of thousands of Mexican cattle, a large number of which
are presumed to be infected with the disease, while protecting the U.S.
cattle industry.
As part of its increased surveillance activities, APHIS is continuing
an education effort to inform U.S. cattle producers and veterinarians
about this pest and the disease that it causes.
For more information, contact:
USDA, APHIS, Veterinary Services
National Center for Import/Export
Animals Program
Telephone: (301) 734–8170
or
USDA, APHIS, Veterinary Services
Emergency Services
4700 River Road, Unit 41
Riverdale, MD 20737–1231
Telephone: (301)734–8073
The U.S. Department of Agriculture (USDA) prohibits discrimination
in all its programs and activities on the basis of race, color, national
origin, sex, religion, age, disability, political beliefs, sexual orientation,
or marital or family status. (Not all prohibited bases apply to all
programs.) Persons with disabilities who require alternative means for
communication of program information (Braille, large print, audiotape,
etc.) should contact USDA's TARGET Center at (202) 720-2600 (voice and
TDD).
To file a complaint of discrimination, write USDA, Director, Office
of Civil Rights, Room 326–W, Whitten Building, 1400 Independence
Avenue, SW, Washington, DC 20250–9410 or call (202) 720–5964
(voice and TDD). USDA is an equal opportunity provider and employer.
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