Saturday, May 04, 2013

Ticks, Lyme disease and horses

Since surfacing as an issue in 1975, Lyme disease has managed to steadily spread. Tick-borne disease, such as Lyme, accounts for 30-40 percent of the equine practice for Lodi Veterinary Care, according to David Kolb, DVM. The disease affects humans with joint inflammation, pain and fever. Unsurprisingly, horses also turn up with similar symptoms when infected, said Corinne Wade, Equine DVM, Lodi Veterinary Care.

In the case of Lyme, the culprit is a tick-borne bacterium called Borrelia burgdorferi, she said, that invades the immune system and causes its trouble. It’s the deer tick (Ixodes scapularis ) that harbors and transmits the Lyme bacteria.

Horse owners are left trying to prevent animals from getting Lyme in the first place and dealing with it once a horse ends up with the infection. Starting with what to do, Wade said there is now a new test for Lyme that can detect disease titers at different stages.

“Knowing what stage the disease is in is important for us in determining a treatment program,” Wade said. But the test costs almost $100, the pain of which is reduced if a stable runs the test on multiple animals and captures the discount for volume.

Treatments involve antibiotics sometimes administered repeatedly for more chronic infections. Anyway you look at it a horse with Lyme disease is a problem. If you can prevent the infection in the first place you are money ahead.

“There is a canine vaccine that shows some promise for horses,” Wade said. “The vaccine isn’t yet approved and it’s not 100 percent effective. But a vaccine creates antibodies in the blood and gives the horse some resistance to the disease.” If approved, the vaccine will cost about $30.

The next preventive strategy is to look at what do about the tick itself, said Kolb. There are basic means of dealing with the tick: avoidance and repellants, habitat control, and insecticides.

“The last 10 years or so we’ve seen a spike in cases of Lyme’s,” Kolb said. “Now, 30 to 40 percent of our equine practice is dealing with tick-borne disease. It’s a regional issue with pockets of problems found in various regions of the country including Wisconsin and Minnesota.”

According to Phil Pellitteri, director of the UW-Madison Insect Diagnostic Lab, the only season deer ticks aren’t a problem is if there is snow cover. Anytime other time you can encounter deer ticks. The ticks like undisturbed grass and brushy areas.

“Mowing makes a big difference,” Pellitteri said. “If you can mow back the edges and keep trails well groomed, the deer ticks are less of a problem.”

Spraying an approved insecticide along edges will kill ticks and knock back populations temporarily. But widespread spraying can become expensive and impractical for large areas. Next in the preventive lineup are various repellants.

“There are some insecticides you can pour on the horse that work well,” Kolb said. “But the top two are toxic to cats. You may not want that in your barn.”

Lodi Veterinary Care now offers kits that include repellant leg bands. The leg bands are generally effective and can last up to three months. There also are repellents and insecticides that horse owners can apply directly to the horse.

“You can apply the material to those areas where the ticks are likely to encounter the horse like the muzzle, legs, chest,” he said. “They’ll need to be re-applied.”

Anytime you work with repellants and insecticides you should take care to read and follow all label instructions and warnings. Because tick-borne infections are regional, some research before heading off on a trail ride is a good idea.

There are various theories for why the tick and its associated Lyme disease continue to spread, Pellitteri said. Kolb explained one notion is related to the White-Footed Mouse, a woodland creature that is host to deer tick. Fox prey on the mice and keep populations in check but there are areas where coyote move in and the foxes leave. Without the fox, the mice population goes up.

“But I think moisture patterns have something to do with it,” Pellitteri said. “The only time I’ve seen a drop in tick populations is because of a drought. They don’t like dry conditions.”

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