Written By Brendt Bonura, DVM –  B-Line Equine Veterinary Services

Original Publish Date June 2014

You may have known that ticks can cause diseases in dogs & humans. But, did you know that horses can be victims too?

Ticks, unlike fleas, tend to proliferate in the colder months. Tick-borne diseases are more common in the northeast. Louisiana is considered a “low risk” state. However, if your pastures are woody, as many are in this region, then your horses might be at risk.

   Ixodes (the “deer tick”) is the most common tick species that can transmit diseases to horses. This tick, like many tick species, has a specific life cycle, during which it must attach itself to hosts along the way. For example, the typical primary reservoir for these ticks is the mouse, and sometimes birds. For the tick to transmit disease, it must be attached to the second host (like a dog, human, or horse) for at least 24 hours. Diseases that these ticks can transfer to horses include Lyme disease & Erlichiosis. The “tropical horse tick,” which is found in Florida & Texas, has been known to transmit Piroplasmosis.

• Lyme disease is caused by a bacterium called Borellia burgdorferi and usually manifests as a “shifting lameness” with stiffness. Some horses will display behavioral changes and perhaps neurologic signs. Uveitis (inflammation of structures in the eye) can also occur.
• Anaplasma phagocytophilum is the organism that causes Equine Granulocytic Erlichiosis (EGE). This bacterium likes to live inside of the host’s white blood cells. Signs include fever, depression, and swelling of the extremities (legs & face). Some horses will display neurologic signs, such as ataxia (stumbling & wobbling).
• Piroplasmosis (Babesiosis) is caused by Babesia protozoa that destroy the horse’s red blood cells, causing anemia and signs such as lethargy, swollen extremities, and fever. It is transmitted from horse to horse through blood contamination (biting insects or contaminated needles). Some horses can become resistant & show no signs, but will carry the disease, increasing the chances of others getting infected. Equine piroplasmosis is rare in the US. To keep it that way, testing is required for horses entering into this country, traveling to some states, and even before setting foot on a race track.

Both Lyme disease & EGE can be treated with tetracycline antibiotics (such as doxycycline), but early detection is the key to a better prognosis. Piroplasmosis is untreatable, unless involved in a USDA research study, and horses that are found positive must be euthanized. There is no equine vaccine for these diseases, but here are a few tips if you are having a tick problem on your farm:

• Cut tall grasses, trim shrubs, and avoid pasturing horses in woody areas during the cooler months.
• Eliminate the ticks’ common primary host, the mouse, i.e. get a “barn cat” or set traps.
• Frontline topical spray for dogs can be used on your horses.
• Get a flock of guinea hens – They eat ticks!
• Clip your horses’ long coats, feathers, etc.

If you find a tick on your horse, remove it immediately, making sure to remove the mouth parts, as the organisms are transferred via the tick’s saliva.