Products approved to fight bluetongue in Montana sheep

BOZEMAN, MT – Sheep producers who are worried about another bluetongue outbreak in Montana now have permission to use three products against the insect that transmits the disease. One product, normally used on cattle, is an ear tag that contains insecticide. The other two are insecticide sprays.

Greg Johnson, a veterinary entomologist at Montana State University, said the Montana Department of Agriculture recently approved the PYthon ear tag, GardStar 40EC spray and Permectrin CDS, an insecticide spray that contains piperonyl butoxide, an additive or synergist to enhance its effectiveness.

Johnson and two researchers in Wyoming tested the products last summer on sheep owned by the University of Wyoming. The insects – also known as “no-see-ums” because they’re so small – came from a colony of biting midges that belong to the U.S. Arthropod-borne Animal Disease Research Lab in Laramie, WY. Working with Johnson were Jack Lloyd, a retired professor from the University of Wyoming and veterinary entomologist, and Will Reeves, a research entomologist with the U.S. Department of Agriculture.

The scientists found that ear tags and spray individually prevented bites and bloodshed for three to four weeks, Johnson said. Used together, they were effective for more than four weeks.

Montana’s bluetongue outbreak occurred in early August last year in deer, antelope and sheep. The outbreak was severe enough that 16 counties, most of them in eastern Montana, were placed under quarantine. Producers in those counties couldn’t ship their lambs to market from about Sept. 1 through early October. Bluetongue also killed 250 sheep in Wyoming’s Big Horn Basin.

Bluetongue is a serious disease whose symptoms include a swollen, blue tongue because of a lack of oxygen to that area. Other symptoms, according to the Montana Department of Livestock, are a crusty, swollen muzzle, lesions or bleeding in the mouth of on the skin, and lameness. Animals may also look depressed and act differently than normal. They may have a high fever and lose wool and muscle strength.

The kind of biting midge infecting sheep, antelope and deer doesn’t feed on humans, therefore humans won’t get bluetongue, Johnson said. Antelope and white-tailed deer are very susceptible to the biting midge. Mule deer, in general, are not.

Johnson and his team of county agents and private citizens are currently trapping midges at seven Montana locations where sheep had bluetongue last year. Those locations are near Billings, Pompeys Pillar, Jordan and Miles City. Midges have been collected so far this summer at each of those sites.

But based on the number of midges collected, Johnson said he thinks another outbreak of the magnitude seen last year is unlikely.

Outbreaks typically require lots of insects, and he hasn’t seen that this year except near Malta, Johnson said. His team there has trapped “zillions” of biting midges, but he doubts they are transmitting bluetongue because he doesn’t know of a bluetongue outbreak there last summer, Johnson said.