October 17, 2007

 

US cattle farmers facing tough battle against fever ticks

 

 

US livestock health officials say cattle farmers are in for a tough fight against fever tick as it will take two years to completely control the pests which can cost US$13 million.

 

The former fever tick-free areas of five counties along the Texas-Mexico border are now heavily infested. 

 

The fever tick, less than 1/8 inches long, is capable of carrying and transmitting "babesia," a blood parasite deadly to cattle.

 

According to Dr. Bob Hillman, Texas state veterinarian and executive director of the Texas Animal Health Commission (TAHC), the fever tick, which started spreading since 1940s, cannot be ignored as it is capable of transmitting a foreign animal disease.

 

He said the fever tick can spread from coast to coast to as far as north as Washington DC except the arid lands of New Mexico and Arizona if it cannot be stopped. Hilllman added that as the tick spreads, so will the need for personnel and resources and it is thus important to "win the battle along the Rio Grande in Texas, and other states won't have to fight the war."

 

TAHC has placed temporary fever tick quarantines on 1,116.3 square miles in five Texas border counties. In addition, an 852-square mile permanent quarantine zone butts up against the Rio Grande from Del Rio to Brownsville, Texas, and is under the management of the US Department of Agriculture's 60-person Fever Tick Force.

 

USDA, which added 30 tick inspectors, and TAHC, which has detailed inspectors to south Texas on a rotating basis, is working with ranchers to locate, corral and eradicate the tick. In this area about the size of Delaware, all cattle, horses, penned deer, llamas, camels and any other species that can host the tick are being manually "inspected" or "scratched" by TAHC or USDA inspectors.

 

Animals will undergo another "scratch" inspection and will be dipped or sprayed with disinfectant if they are moved from their premises.

 

When fever tick-infested livestock are detected, the premises are quarantined for six to nine months. As of early October, this included at least 25 premises in the temporary quarantine areas and about 56 premises in the permanent quarantine zone.

 

USDA has made US$340,000 available for immediate fever tick needs in south Texas, and the state legislature granted TAHC an extra $150,000 to purchase additional Co-Ral, the acaracide used for dipping vats and in spray rigs, Hillman said.

 

He reported that a USDA report concluded that it will take US$13 million to completely eliminate fever ticks as it the operation would need additional personnel, repair or replace worn out portable tick-dipping equipment, buy new spray facilities and other necessities.

 

Tracing the movement of cattle is also important to control fever tick, says Hillman, Currently, TAHC field staff has checked nearly 800 animals and about 459 have been located, inspected and found to be fever tick free. These are found in Kansas or Texas Panhandle feedyards, and others were scattered across the state and to two other states.

 

The fever tick, by itself, will not cause disease. However, cattle tick fever is imminent if the fever tick is carrying babesia and transmits it to cattle, meaning they have no resistance to the organism that quickly breaks down red blood cells, noted Hillman. There are two potential scenarios with fever ticks that keep TAHC, the Tick Force and border ranchers awake at night, he said.

 

The first scenario, Hillman explained, involves Mexico, where fever ticks and babesia have not been eradicated. Young calves there may be exposed to babesia, survive the disease and develop immunity but continue to carry the organism.

 

Even if Mexican feeder cattle carry babesia, they will not cause a disease problem unless there is fever tick involvement, explains Hillman. Mexican-origin feeder cattle enter the US under strict USDA fever tick inspection and dipping requirements. To keep them away from fever ticks, Hillman says TAHC requires Mexican-imported cattle to have an 'M' branded on their hip and prohibits these animals from being maintained in the permanent quarantine zone."

 

If fever ticks are moved to sites where Mexican feeder cattle are pastured, the pests may pick up babesia, says Hillman. The babesia-infected female tick transmits the disease to the next generation of fever ticks. Only one element then would be missing from the dangerous disease equation: US cattle with no immunity to the babesia, noted Hillman. It's crucial therefore to keep the fever tick pushed beyond the border and support and fund surveillance activities in the permanent fever tick quarantine zone, he stressed.

 

Hillman said the second scenario involves wildlife as effective alternative hosts and sources for movement of ticks into Texas from Mexico and from the permanent quarantine zone to the free area of Texas. Elk, white-tailed deer, nilgai and red deer serve as effective hosts for fever ticks but are not affected by babesia.

 

According to him, treating wildlife is a tricky proposition because current methods are limited to feeding cervids ivermectin-treated corn or drawing them to 'four-poster' stations where they rub against pyrethrin-treated posts, which transfers the chemical.

 

The fever tick is not a human health threat, however, Hillman said, getting ticks to other sites is easy. He added getting and keeping the fever tick out of Texas and the US is critical for disease control and our continued ability to move livestock without restrictions.