Keeping cattle fever ticks away from U.S. herds

Kerrville, Texas-Agriculture Research Service (ARS) scientists have shortened the time needed to spot tick resistance to pyrethroids in Mexican cattle.

The discovery will help keep U.S. borders safe from cattle fever ticksthat can transmit bovine babesiosis, officials say.

Despite being eradicated in the United States, cattle fever ticks stillpersist in Mexican cattle, many of which cross the border for U.S. markets.

A quarantine zone in south Texas along the Mexican border is currentlythe only barrier to cattle fever ticks' re-entry into the United States,where all cattle are susceptible to the disease the ticks carry.

To prevent a reinfestation, U.S.-bound animals are "dipped"in coumaphos, an organophosphate pesticide that kills the ticks. But someMexican ticks have developed resistance to coumaphos and other pesticidesused in Mexico. So ARS scientists at the Knipling-Bushland U.S. LivestockInsects Research Laboratory in Kerrville, Texas, have been looking for waysto monitor resistance in Mexican ticks.

ARS physiologist Felix D. Guerrero and microbiologist John H. Pruetthave identified two independent mechanisms by which ticks become resistantto pyrethroid pesticides still used in Mexico. And they have found one strainof resistant Mexican tick possessing a gene that produces a large amountof a specific esterase protein involved in the breakdown of pyrethroids.

Guerrero and Pruett have shortened the time needed to spot pyrethroidresistance in a specimen from six weeks to just one day.