It's been called the silent war, a constant vigil of unsung heroes, many of them riding the Texas-Mexico border by horseback keeping guard, others working in laboratories checking Rhipicephalus annulatus and R. microplus, or ticks, for Babesia bovis ( Babesia bigemina is also a concern.), a deadly cattle disease better known as Cattle Fever, or Bovine Babesiosis.
The tick, and the disease it carries, has the devastating potential to cripple the U.S. cattle industry if not contained, much as it did in 1906, the first year the disease was discovered in the continental United States. In the first decade of the 20th century, direct and indirect economic losses to Cattle Fever were estimated to be $130.5 million, or about $3 billion in today's economy.
While eradication efforts have been ongoing for over a century, infected cattle and other types of ungulates have been discovered infected with the tick from time to time, the most recent being in May and June this year (2014) in Cameron County in Deep South Texas. The continuing eradication program, including the inspection and detection of tick infestations, is once again proving to be not only useful, but also necessary to prevent a repeat of a devastating disease outbreak to the U.S. cattle industry.
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Two premises and three cattle herds have been quarantined by the Texas Animal Health Commission (TAHC) and USDA-APHIS for the presence of Cattle Fever ticks in recent times, and officials have confirmed that African antelopes that populate South Texas pose an additional threat to spread the parasites. Consequently, federal authorities have announced a plan to reduce the population of these exotics in the suspect areas.
The Cattle Fever Tick Eradication Program (CFTEP) was established to eliminate bovine babesiosis from the U.S. cattle population in 1907. The program is a joint state-federal initiative because the disease is a severe and often fatal threat to cattle. It is generally characterized by extensive loss of red blood cells due to the breakdown of a cellular membrane that leads to anemia, jaundice, and death. Infected cattle may exhibit neurological disturbances characterized by incoordination, seizures, muscle tremors, hyper excitability, aggressiveness, blindness, head pressing, and coma, followed by death.
In addition, the two tick species responsible for carrying the disease are capable of causing blood loss, significant damage to hides, and an overall decrease in the condition of livestock.
Since 1907 the CFTEP has patrolled the southern borderlands to prevent infected strays from wandering across the river from Mexico. A permanent quarantine for a thin stretch of property located along the U.S./Mexico border in eight South Texas counties has been under quarantine for 107 years. This area includes property ranging from a few hundred yards up to seven miles wide along the border, beginning on the tip of Texas near Brownville and north up the Rio Grande to Amistad Reservoir near Del Rio, about 150,000 acres of border land in all.
USDA-APHIS tick riders constantly control this thin strip of land and are vigilant for animals displaying symptoms of the disease. In addition, a comprehensive inspection takes place at border checkpoints for all animals entering the U.S. from Mexico.
Nilgia infection complicates the issue. USDA-APHIS officials say nilgia were introduced at the King Ranch in the early 1940s, and because they are known to migrate great distances in search of forage, the population has grown since the exotic antelope was introduced as a game animal for hunters. Recent estimates indicate as many as 36,000 nilgai currently in Texas.
In a report issued by APHIS this week, nilgia are a large species (males weigh in excess of 600 pounds) and can easily compete with cattle and native deer for food and water. White-tailed deer prefer forbs and browse, but consume little grass. If forbs and browse become scarce from competition or weather-related events, wildlife officials say nilgai may shift their diet to grass; white-tailed deer are unable to do so and subsequently can suffer from malnutrition. The ability of nilgai to consume a variety of resources also can affect the carrying capacity of an entire range.
In February 2007, APHIS Mounted Patrol Inspectors (MPI) were presented with a harvested nilgai antelope they had trailed from privately-owned land to U.S. Fish and Wildlife Service (FWS) property at Boca Chica Beach, a tract of land near the Rio Grande in Cameron County. The animal and was infested with southern cattle ticks. The immediate area was immediately placed under temporary quarantine.
In March 2009, after cattle fever tick infestations were found on nearly 25 percent of the nilgai antelope harvested from the FWS property of Boca Chica Beach, the quarantine status for the FWS property was changed to infested. In April 2013, a nilgai that had been privately hunted was scratch-inspected and found infested with cattle fever ticks, confirming the continual presence of infestation in the area.
The Boca Chica Beach Area consists of approximately 42,000 acres. Approximately 22,400 acres of this area is owned by FWS. In addition to the Boca Chica Beach Area infested quarantine status, one private premise, immediately adjacent to the Rio Grande, is quarantined as infested, and one of three cattle herds in the area also is quarantined and termed infested. The other two herds in the area remain at risk of infestation.
In addition to the FWS land at Boca Chica, additional areas along the Port of Brownsville ship channel and property surrounding the communities of Port Isabel and Laguna Vista are increasingly known grazing areas for exotic nilgai, and harvesting these exotic herds is being proposed in these areas.
Federal wildlife officials say without additional effort to prevent the further spread of ticks via nilgai that inhabit the Boca Chica Beach Area, Brownsville Navigation District property, and Bahia Grande area, tick infestations likely will continue to spread up the coast and into areas with even greater numbers of high risk cattle populations. As a result,
USDA-APHIS plans aerial harvesting of nilgai in the Boca Chica Beach Area of Cameron County. Also, APHIS proposes aerial harvest of nilgai in the Bahia Grande area and Brownsville Navigation District property as well, followed by surveillance and ground harvesting after the quarantines are lifted.
The extent of herd reduction in nilgai in the defined areas is unknown, but authorities say they only plan to reduce a small percentage of the animals and test those that have been taken. Thinning of the population of nilgai, if effective, may clear the way for an annual hunt to maintain a steady population level that would help prevent the spread of Cattle Fever ticks.
Once tested, the plan calls for carcasses to be donated to area food banks.
The plan is based upon a comprehensive assessment and will not be put into action until after a public comment period. A bulletin issued by USDA-APHIS on July 11 calls for an immediate comment period which will close 30 days later on Aug. 12, 2014.
The public and other interested parties are encouraged to submit all comments on the environmental assessment by August 12, 2014, to Matthew.T.Messenger@aphis.usda.gov. Comments may also be submitted via first-class mail or by fax (to the following address and telefacsimile number).
Cattle Fever Tick Eradication Program
Animal and Plant Health Inspection Service
U.S. Department of Agriculture
4700 River Rd., Unit 43
Riverdale, MD 20737
Fax: (301) 734-4982
A copy of the environmental assessment titled “Population Reduction of Nilgai in the Boca Chica Beach, Bahia Grande, and Brownsville Navigation District Areas, Cameron County, Texas" can be accessed at: