Ticks lurk everywhere our horses go, from the trail to the stables to the pasture. Most horses will get bitten by a tick during their lifetime, and there’s a good chance they will contract a tick-borne infection. Many remain asymptomatic, but others suffer chronic illness after a tick bite. Learn about the most common tick-borne diseases in horses and how you can keep your horse safe.

Anaplasmosis in Horses

The number one most common tick-borne disease in horses is anaplasmosis. Anaplasmosis is transmitted by the deer tick, which is found across most of the United States.
In mild cases, anaplasmosis causes a high fever that begins around five days after infection and may last about a week. It also causes mild swelling in the limbs, loss of appetite, and impaired coordination. It’s possible for mild cases to clear up within a few weeks without treatment. The infection is not contagious to humans or other horses; it can only be transmitted through deer tick bites.
Adult horses, especially seniors, are more susceptible to severe symptoms of anaplasmosis. They may develop jaundice, red spots on the whites of their eyes, and neurologic symptoms like seizures or tremors. The infection is rarely fatal unless accompanied by a secondary infection.
Horses with anaplasmosis often seem to recover after a few weeks but may then relapse. Once fully recovered, they will be immune to the bacteria for two years.

Lyme Disease in Horses

The second most common tick-borne disease in horses is Lyme disease. As many as 75% of horses have antibodies that indicate they have been exposed to Lyme, but diagnosed, symptomatic cases are relatively uncommon. Even so, with milder winters each year, tick populations have been increasing and they’re being found across more regions of the United States. As a result, reports of Lyme disease in horses are increasing each year.
Lyme disease often goes undetected in horses. Though the tick must be attached for at least 24 hours to transmit the bacteria that causes Lyme disease, it may fall off before it is noticed. Horses can get the bulls-eye shaped rash, too, but it may not be noticeable under their coat.
Symptoms of Lyme disease can imitate those of more common conditions. Joint stiffness and inflammation are common but often misattributed to arthritis or a joint injury. However, joint inflammation associated with Lyme disease can be intermittent and may shift from limb to limb. Other nonspecific symptoms include unexplained weight loss, lethargy, difficulty swallowing, fever, and laminitis.
Lyme disease in horses responds well to antibiotics, but joint damage, neurological symptoms can persist for months.

Equine Piroplasmosis or Babesiosis in Horses

Piroplasmosis, also known as babesiosis, is tick-borne parasitic disease that’s rarely seen in the United States. In 2020, just 23 US cases were reported, almost all quarter horse racehorses. However, it’s more common in other countries, so it’s good to know if you ever travel with your horse.
Horses that contract the parasite develop symptoms within one to three weeks. Symptoms include weakness and fever, jaundice, poor appetite, trouble breathing, and a swollen belly. Piroplasmosis has been reported to be fatal in around 5-10% of horses. Horses in endemic countries seem to have a better prognosis, as they may receive antibodies from their mother or early life exposure.

Protect Your Horse From Tick-Borne Illnesses

Ticks can be found in tall grasses, woodpiles, shrubs, leaf piles, and other moist, shaded spots, so keeping your property trimmed and uncluttered can help keep them away. They contract disease-causing bacteria by feeding off infected deer and mice. Keep your property free of food sources for wild animals like uncovered bird feeders and open grain bins.
When spending time in tick-infested areas is inevitable, protect your horse with Absorbine UltraShield EX Fly Spray to repel ticks, mosquitoes, and other biting pests.