New Cattle Disease Detected in Tennessee

Aug 01, 2022


A new, potentially dangerous, disease of cattle has been reported in Tennessee. Theileria orientalis Ikedia, which is a protozoan known to be carried by the Asian longhorned tick (ALT), has been diagnosed in a herd in Middle Tennessee.
Theileria orientalis infects red and white blood cells and causes bovine infectious anemia. Clinical signs of theileriosis in cattle include anemia, jaundice, and weakness, says University of Tennessee Extension veterinarian Dr. Lew Strickland. “Native genotypes of T. orientalis in the United States are usually nonpathogenic; however, Theileria orientalis genotype Ikeda is a virulent strain that is novel to U.S. cattle. T. orientalis Ikeda infections have been reported to cause mortality in up to 5% of infected cattle.” Pregnant heifers and calves are particularly susceptible to the infection, he adds. Clinical findings include weakness, reluctance to walk, and abortion. Physical examination may reveal pale mucus membranes, high fever, and elevated heart and respiratory rates.
Strickland says cattle that recover from Theileria infections usually become carriers, which is a source of infection for other cattle in the herd.
There is not an approved effective treatment or vaccine for T. orientalis. Because of this, Strickland says prevention and biosecurity are imperative. He recommends these steps:
Prevention and Control
  • Regularly inspect cattle for ticks. The ALT is small and may go unnoticed with only a quick look. Focus on the head and the neck, but also check the flanks and back, the armpits and groin, and under the tail. Tick larvae, nymphs, and adults may all be found at the same time on a single animal.
  • Cattle with low weight gain, are lethargic or anemic, have patchy hair, or generally look unthrifty should always be inspected for ticks.
  • Animals may have large numbers of ALT, but only a few ALTs may be sufficient to transmit cattle disease. Submit tick samples to your local county Extension agent or veterinarian for species confirmation.
  • Once ALT is confirmed on your animals, you should assume it is established in the area and management for this tick will be a continuing process.
Chemical Control
  • There appears to be an elevated risk of cattle disease transmission by ALT February through March and August through September. Tick control is highly recommended during these time periods, but ALTs are active during much of the year. Consider chemical control for ALT from March into November.
  • A single pesticide application method may not be fully effective against ALT. Consider using pesticide-impregnated ear-tags along with backrubbers and other devices.
  • Use permethrin or organophosphate ear tags. However, ear tags will not be effective in all areas that the tick prefers. Do not mix classes of chemicals with insect control. Use the same class of chemicals for one to two years, then rotate.
  • Use backrubbers and siderubbers (“bullets”) or similar devices charged with permethrin. Hang rubs in such a way that cattle must contact the rub as they move past, spreading the pesticide along the top of their bodies. Vertical strips hung from a backrubber help apply material to the head and flanks as the cattle move past.
  • Recharge devices regularly following the pesticide label. ALT management may require recharging devices every 2 to 3 weeks.
  • Use pour-on permethrin at the rate recommended on the label. Apply along the topline of the animal in a narrow strip, starting at the back of the withers and continuing all the way to the tail head. Be aware that heavy rain may wash pesticides off the animal. Increased fly burdens at several days after a heavy rain may indicate the need to retreat the animal.
  • Treat all animals in a herd for ticks at the same time. Apply formulations specifically labeled for tick control. Follow all label recommendations for pesticides (including ear tags, backrubbers, pour-ons, etc.) used, including time to retreat, withdrawal periods, beef vs. dairy, lactating vs. dry, use of personal protection, etc.
  • Chemical treatment of pastures is not recommended except when tick populations are extremely large. Carbaryl (Sevin) labeled for use on pastures should be restricted to sections of the pasture with the highest number of ticks. Pasture treatments should be used in conjunction with other treatments.
  • Chemical control greatly reduces tick burdens on animals but does not eliminate the chance of ticks, tick bites, or acquiring tick-borne diseases.
Herd Management
  • Inspect purchased cattle for ticks and treat if found before adding to the established herd.
  • Consider having animals tested by a vet for tickborne disease if ticks are found on them, especially if the cattle are not gaining weight, have patchy hair, appear lethargic, or show symptoms of anemia.
  • Keep pastures mowed short as long grass and brush enhance ALT survival. Leaving pastures ungrazed will not control ticks as they can survive about a year without feeding. Wildlife in the ungrazed pastures will support tick survival in the absence of cattle, too.
  • Mow pastures short before rotating stock back into them, even if the cattle have been treated for ticks.
  • Keep cattle out of wooded areas. If possible, fence cattle 20 feet away from wooded areas.
  • Wildlife, such as deer, small mammals, and birds, can serve as alternative hosts for ticks and assist their spread.
  • Check pets if any ticks are found on cattle.
  • People working in areas infested with ticks of any species should inspect themselves regularly for ticks.
Strickland adds that monitoring the movement of the ALT is imperative to future prevention efforts. Rebecca Trout-Fryxell, an associate professor of medical and veterinary entomology with UT, has distributed tick collection kits to local county Extension agents for collection and submission of ticks. If you find ticks on your cattle, contact your local Extension agent or veterinarian so that the tick can be submitted for identification.
Producers with questions may contact Strickland by email at lstrick5@utk.edu, or at askdrlew.tennessee.edu.

More information is available from the Tennessee Department of Agriculture at this website. For more content like this, check out the latest issue of The Cooperator.
 

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