4 July 2008

6 minute read

North America

Fever ticks, capable of carrying and transmitting deadly "tick fever" to cattle, have been detected on livestock or wildlife on 139 Texas pastures during the past 12 months.

"In July 2007, the first preventive quarantine was established--39,325 acres in Starr County--to enable the US. Department of Agriculture's Tick Force and the TAHC to inspect and treat livestock moved from the area, get ahead of the fever tick and push it back across the quarantine line," said Dr. Bob Hillman, Texas' state veterinarian and head of the Texas Animal Health Commission, the state's livestock and poultry health regulatory agency. "Now, a year later, we have more than a million acres under preventive quarantines in Starr, Zapata, Jim Hogg, Maverick, Dimmit and Webb counties, in addition to the half-million acres in the permanent fever tick quarantine zone that runs alongside the Rio Grande, from Del Rio to Brownsville."

The enlarged preventive quarantine includes portions of Starr, Zapata counties and a small area in Jim Hogg County. It is bounded on the north by Texas Highway 16, from its intersection on the west with US Highway 83 to its eastern junction with Ranch Road 649. Ranch Road 649 is the eastern boundary to its southern intersection with US Highway 83, which is the western boundary stretching northward to the intersection with Texas Highway 16. Maps of this and all preventive fever tick quarantines are available on the TAHC website at http://www.tahc.state.tx.us or by calling the TAHC at 800-550-8242.

"This is no longer a 'border war' against the fever tick," said Dr. Hillman. "The fever tick has gained a substantial foothold on Texas soil, and without adequate resources to fight this pest, it will spread." The fever tick, which can survive winters from coast to coast and as far north as Washington, D. C., was successfully pushed back into Mexico in 1943. Periodic tick incursions since then have occurred in Texas, but only one, in the 1970s, eclipsed the current outbreak for the number of premises infested and took six years to eradicate.

"In smaller states, a quarantine area the size of Delaware would raise red flags," said Dr. Hillman. "Texas' vastness and the previous success at keeping the fever tick controlled may be working against us. Now we need help, with a million more acres to cover and finding about a dozen infested premises a month."

"Early this year, the fever tick program received $5.2 million of the $13 million of federal funds requested to fight the tick, and while appreciated and used, it is not enough to win this battle," said Dr. Hillman. "Furthermore, there has been no funding for the National Fever Tick Eradication Strategic Plan, developed and approved by USDA in 2006. It called for preventing entry of cattle fever ticks into the U.S., enhancing surveillance, and eradicating infestations resulting from fever tick incursions. The plan also was to identify and procure the tools necessary to keep the U.S. free of fever ticks, and to work with Mexico, where cattle fever ticks are not controlled. The strategic plan has not been implemented."

"It's really a 'pay now or pay later' scenario, because this tick won't be stopped with less than an all-out assault that requires adequate personnel, sufficient treatment products, and enough equipment, such as portable dipping vats or portable spray boxes for cattle, and treatment equipment for deer and other wildlife hosts," said Dr. Hillman. "Texas has a ticking time bomb in south Texas. So far, we have had only two of the three elements for a 'tick fever' outbreak--fever ticks and fever tick hosts--including cattle, horses and several species of wildlife. If, however, some of these fever ticks carry babesia, a blood parasite deadly to cattle, the equation would be complete and we could see livestock death losses."

On the front lines are the ranchers in the preventive quarantine areas who must gather their cattle for inspection-which in the south Texas brush country usually requires helicopters and cowboys on horseback. The TAHC and USDA work cooperatively to provide the inspections to determine the scope of infestation in the area. Cattle, horses and ruminants, including llamas and camels, also must be inspected, treated and permitted prior to leaving the area.

Dr. Hillman encouraged ranchers to comply with the preventive quarantines and asked producers in adjacent counties to have their livestock checked prior to movement out of the area. "In discussions with ranchers, it has been suggested that cattle moving through south Texas livestock markets be inspected and dipped prior to sale," said Dr. Hillman. "This is being considered, but it, too, requires additional personnel, chemicals and the construction of dipping vats, resources we do not have at this time."

"We have traced more than 1,000 cattle moved from ranches later found to be tick-infested," said Dr. Hillman. "Requesting an inspection prior to movement costs nothing for the rancher, but it could save us countless hours of tracking cattle, time that could be better used in the field to fight the ticks. I also encourage ranchers anywhere in Texas to call us if they see tick infestations on their cattle. We can check the animals, and collect and send tick samples to the state-federal laboratory for identification. We do not want to take any chances with these ticks and spread them further." Ranchers can call their area TAHC office, or the agency headquarters at 800-550-8242.

Ranches where ticks have been detected are quarantined, and cattle are rounded up, inspected and treated as often as every two weeks, or as seldom as every 28 days, depending on the treatment method-dipping, spraying or injection with Dectomax, an injectable treatment. The cattle are repeatedly treated and returned to the pasture to 'pick up' ticks on the vegetation, until the animals are tick-free, indicating that the premises is free of the pests.

Another method of clearing a pasture of ticks involves removing clean, treated cattle and 'vacating' the pasture for as long as nine months to starve out the ticks. Recently, this method has met with less than positive results, as ticks have demonstrated their adaptability to live on wildlife when cattle hosts are not available.

"Historically, fever ticks preferred cattle, and sometimes, hitched a ride on horses. Now fever ticks are being detected not only on white-tailed deer and nilgai, but also on aoudad sheep, fallow, axis and red deer, and elk. Fighting fever ticks on a variety of species--especially free-ranging animals that don't respect fences--makes this battle much more difficult," said Dr. Hillman.

Currently, treatment of wildlife or exotic livestock is limited to providing corn treated with an insecticide, or setting up feeding stations equipped with treated posts that transfer pyrethrin, an insecticide, to the animal's head and neck. Later, as the animal grooms itself, the pyrethrin is distributed across its body, killing the fever ticks. The problem: some products require a 60-day withdrawal period, so they can't be used just prior to or during the hunting season. In the quarantined areas, the hides of harvested animals are either left behind, or inspected and treated prior to being removed from the premises.

"Concerns about fever ticks run deep in Texas, where the TAHC was established in 1893 to fight this pest. A Fever Tick Working Group, with industry and related agency membership, is working on recommendations for getting ahead of the fever tick, so it can be pushed back to the border. Likewise, a Wildlife Subcommittee also is working on suggestions for addressing fever ticks on free-ranging and exotic livestock," said Dr. Hillman. "Fighting fever ticks may seem simple, but it's not easy.and it's never cheap."

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