Tick-borne Diseases and Tick Prevention for Horses

Learn more about tick-borne diseases and tick prevention for horses including three of the most common types of tick-borne diseases that affect horses.

Long hot days and pesky flies may be your biggest concern when keeping your horse comfortable this summer, but have you considered protection from ticks? Some of the biggest threats to your horse’s health and comfort come in the form of small pests, one of the most formidable being ticks. Being in-the-know about the most common types of tick-borne diseases that affect horses as well as having an appropriate tick prevention strategy in place can help you keep your horses happy and healthy this summer—and all year—long. 

What diseases do ticks carry?

Close up photo of adult deer tick

Lyme disease, equine piroplasmosis and anaplasmosis are three of the most common types of tick-borne diseases that affect horses. 

“As far as we know, those are the three big ones. In the past year, we’ve discovered other tick-borne viruses, but we don’t have enough research to know if these can also be transmitted to horses,” says Jennifer Thomas, DVM, a veterinarian at the Center for Veterinary Health Sciences at Oklahoma State University and an affiliate of the National Center for Veterinary Parasitology.

A big challenge for both horse owners and veterinarians is that tick-borne disease can present with nonspecific clinical signs, so veterinarians have to consider numerous possibilities before arriving at a specific diagnosis.

Lyme disease in horses

Lyme disease is transmitted by ticks carrying Borrelia burgdorferi, an infective organism known as a spirochete that is specifically found in the tick species Ixodes scapularis (black-legged tick) and Ixodes pacificus (western black-legged tick), both of which are commonly referred to as “deer ticks.”

Make sure you are checking your horse for ticks on a regular basis

Diagnosing Lyme disease can be an investigative process. Oftentimes Lyme disease isn’t suspected unless the horse lives in or has traveled to an area known to have ticks infected with B. burgdorferi and ticks have been found on the horse. The veterinarian will look for clinical signs while at the same time rule out other causes of those clinical signs. 

Lyme disease is considered acute if it is diagnosed within the first weeks after exposure and chronic if the infection persists for months. Signs can be vague and varied, depending on the tissues affected. They include generalized stiffness, lameness that shifts from limb to limb, swollen joints, weight loss, sensitive skin, lethargy, behavioral changes or rarely uveitis (inflammation of the eye). The horse may just generally not feel good or develop a surly attitude.

Lyme disease is difficult to diagnose because exposure to the bacterium alone is not proof of illness and the outward signs mimic so many other problems. For that reason, other illnesses and injuries are generally ruled out before a Lyme diagnosis is made. Treatment usually consists of a course of antibiotics.

What is equine piroplasmosis (EP)?

Equine piroplasmosis is a general term given to infection with either Babesia caballi or Theileria equi (formerly called Babesia equi). Both of these blood parasites can be transmitted by several species of ticks. Infected horses may have few or no clinical signs which can include mild to general weakness, depression, rapid shallow breathing, lack of appetite, weight loss, jaundice, dark-colored urine and abortion in pregnant mares. In more acute phases, the horse will tend to have a high fever (over 104 degrees Fahrenheit), pale or yellow mucous membranes and lower limb swelling. The disease can affect horses, mules, donkeys and zebras. 

It is important to note that EP is currently not endemic to the United States, Canada, Australia, Japan, England, Ireland or Iceland. Horses imported into the United States from endemic areas must undergo quarantine and testing to ensure that they are not carrying antibodies to either of the two protozoa that cause EP.

What is equine anaplasmosis?

The same ticks that transmit the Lyme disease organism can also carry the bacterium responsible for anaplasmosis (previously known as ehrlichiosis). It’s possible for a horse to have both at once and tends to occur in young horses, often under four years old. Signs of illness don’t usually appear for eight to 14 days after the infected tick feeds on the horse. Fortunately, anaplasmosis is rarely fatal and is easy to treat.

The bacterium infects white blood cells and causes signs like high fever as well as depression, lethargy, poor appetite, jaundice, ataxia and edema in the legs. Antibiotics—primarily oxytetracycline and tetracycline—can eliminate the infection. The good news is horses remain immune once the infection clears. 

Protecting your horse from tick-borne diseases

“I would never consider any tick on a horse to be a ‘safe’ tick,” cautions Thomas. “We keep discovering new viruses and bacteria that they can transmit, so I wouldn’t feel safe saying there’s any tick that doesn’t transmit a disease.”

The best way to prevent your horse from becoming infected with a tick-borne disease is by having an effective tick prevention strategy in place. Always check your horse for ticks daily, especially after rides in wooded areas.

Farnam Equi-Spot tick repellent being applied

You may also consider using tick prevention for horses. Equine spot-on insect control products first came on the market in the mid- to late-1990s, with Farnam’s Equi-Spot Spot-on Protection for Horses debuting in 2002. Smart horse owners have been taking advantage of the easy to use equine tick prevention ever since.

The ingredients and formulation in Equi-Spot Spot-on Protection for Horses are especially effective against ticks, killing and repelling ticks that may transmit Lyme disease. This is important news for horse owners with the increased concern about the recent rise in tick-borne diseases. One application provides continuous weatherproof protection for up to 14 days making it ideal for situations when you can’t see the horse every day to spray a repellent.

The disease threats from ticks may be ever-present, but knowing how to protect your horse and having a tick prevention strategy in place can help keep the risks under control. Your continued vigilance can go a long way toward keeping your horse healthy this summer.

For more tick prevention tips and tricks, check out this EQUUS Short Take.

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