Newsdate: May 1, 2025 11:30 am
Location: LEXINGTON, Kentucky
Spring has officially sprung in Kentucky with flowers in full bloom and the horses off to the races! While we may be excited to get outdoors and enjoy the sunshine after a long winter, the warm weather also draws out other critters… ticks.
Ixodes scapularis - Blacklegged (Deer) Tick.
To reduce equine tick exposure, environmental, behavioral and chemical strategies are available to reduce the number of ticks and reduce equine exposure to areas where ticks are common.
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Often overlooked compared to mosquito-borne pathogens, ticks are capable vectors of several equine diseases and can cause adverse effects ranging from local irritation to acute and chronic disease. Proactive tick management is an essential component of equine preventive care, particularly as many regions continue to report increased numbers of tick bites and changes in tick species distributions.
In the United States, notable tick-borne diseases affecting horses include:
• Equine Granulocytic Anaplasmosis (Anaplasma phagocytophilum) – most commonly observed signs of infection include fever, lethargy, limb edema and ataxia. In equines, A. phagocytophilum is most commonly transmitted by the blacklegged tick (Ixodes scapularis) in the Northeast, Midwest and parts of the Southeast, but may be transmissible by the Western blacklegged tick (Ixodes pacificus) on the West Coast.
• Lyme Disease (Borrelia burgdorferi) – although horses are less susceptible than dogs or humans infection can result in chronic weight loss, shifting lameness, behavioral changes, and neurological signs. This disease can be difficult to diagnose in equines, as a positive blood test indicates exposure to the pathogen but not necessarily current disease status. Lyme Disease is also transmitted by I.scapularis.
• Equine Piroplasmosis (EP) – caused by Babesia caballi and Theileria equi. This disease is reportable in the mainland U.S., but endemic in Puerto Rico and the U.S. Virgin Islands. Transmission can occur through tick bites (most commonly from Dermacentor or Rhipicephalus spp.), but most U.S. outbreaks or reports of disease are associated with iatrogenic transmission from contaminated equipment during unsanctioned racing events or through illegal importation of infected Quarter Horse racehorses.
• Tularemia (Francisella tularensis) – a rare tick- borne zoonotic disease in horses, associated with Dermacentor spp. and Amblyomma spp. ticks. This pathogen can be transmitted through bites from fleas and flies and through contaminated water sources, but is most commonly associated with tick bites. While rare in horses, it is of veterinary and public health significance due to its ability to persist in the environment, multiple modes of transmission and zoonotic disease potential.
• Tick Paralysis and Hypersensitivity – Toxins in tick saliva may cause neuromuscular dysfunction or localized inflammatory responses in sensitive animals. Emerging Tick species: Asian Longhorned Tick The Asian longhorned tick (Haemaphysalis longicornis) is an invasive species that has been detected in numerous U.S. states along the East Coast and Appalachian Mountains, including Kentucky, where it has been detected on wildlife, cattle, equines, dogs and people.
• It reproduces asexually via parthenogenesis, enabling rapid population growth and large infestations, particularly on livestock.
• This tick has been documented on horses in the U.S., although no confirmed cases of equine disease have been associated with it.
• Internationally, H. longicornis can transmit pathogens of veterinary and medical concern, causing diseases such as anaplasmosis, babesiosis, ehrlichiosis, theileriosis and rickettsiosis.
• Its ability to cause anemia and death in cattle raises concern for similar effects in heavily infested horses, particularly if infestations go unnoticed, though such cases have not yet been reported.
• As horses can develop hypersensitivity reactions to tick and other arthropod bites, even mild infestations of H. longicornis could exacerbate stress, pruritus and allergic dermatitis, affecting welfare and performance even in the absence of pathogen transmission.
Most Common Equine-Associated Tick Species in the U.S.
• Amblyomma americanum (lone star tick)
• Amblyomma maculatum (Gulf Coast tick)
• Amblyomma mixtum (Cayenne tick)
• Dermacentor albipictus (winter tick)
• Dermacentor andersoni (Rocky Mountain wood tick)
• Dermacentor variabilis (American dog tick)
• Haemaphysalis longicornis (Asian longhorned tick)
• Ixodes scapularis (blacklegged tick)
Integrated Tick Prevention and Property Management
Most tick species tend to prefer habitats with shade, moisture and vegetation, including wooded edges, brush and tall grasses commonly found on or adjacent to horse properties, or along trail riding locations. To reduce equine tick exposure, there are environmental, behavioral and chemical strategies available to reduce the number of ticks on the property and reduce equine exposure to areas where ticks may be more common. This can include pasture and property management toreduce areas that are more likely to harbor ticks andreduce wildlife from bringing ticks onto the property.
Integrated management also includes on-animal prevention strategies to reduce ticks from attaching to animals and removing ticks quickly when they do
attach to animals.
Pasture and Property Management
• Mow and maintain pastures frequently to reduce habitat more likely to harbor ticks.
• Create buffer zones between wooded or brushy areas and paddocks.
• Remove brush, leaf litter and overgrown field margins.
• Exclude wildlife (e.g., deer, raccoons) via fencing or deterrents to reduce tick introduction and movement of disease-causing pathogens.
• Control rodents through exclusion and secure feed storage; rodents serve as reservoirs for immature ticks and several tick-borne pathogens.
On-Horse Prevention
• Perform daily tick checks, focusing on thin- skinned, less-visible areas such as ears, eyelids, muzzle, chest, belly, mane and tail. Full body tick checks are recommended after equines have been in areas where ticks may be more common, suchas after trail rides in brushy habitat.
• Apply EPA-registered pyrethroid-based sprays labeled for equine use. Reapplication may be needed based on rainfall or sweat exposure and is typically only effective for short-term applications.
• Fly sheets or insect barriers may provide partial protection from both biting flies and ticks.
• Avoid off-label or overuse of pesticide products to prevent skin irritation or systemic absorption.
Consultation with a veterinarian before application of on-animal chemical products is highly recommended
When to Heighten Vigilance
• After trail rides or turnout in brushy or wooded areas.
• During peak tick activity months: spring through fall, although milder winters may support year- round activity in parts of the Southeast and South Central U.S.
Veterinary Role in Surveillance and Education
Veterinarians are well-positioned to contribute to equine welfare through owner and caretaker education on tick-borne diseases and bites and preventative approaches for tick and other arthropod-borne diseases and associated conditions. In many states, ticks can be submitted for identification through the state’s Departments of Agriculture, Environmental Health or Public Health Departments, or through state Extension services. In Kentucky, suspected Asian longhorned ticks can be submitted through the University of Kentucky Cooperative Extension Service by bringing them to your county Extension office, mailing them to the Entomology Department through the contact information below or by contacting the Office of the State Veterinarian at statevet@ky.gov.
For identification of suspected Asian longhornedtick in Kentucky, please preserve specimens in ethanol or hand sanitizer (without additives like aloe), or in a ziplocked bag after freezing specimens (to kill ticks).
Mail specimens to University of Kentucky Veterinary Entmologist, Dr. Hannah Tiffin, at the address below along with information on date of collection, host animal collected from, county of collection and follow- up contact information.
Hannah Tiffin, PhD
Assistant Professor
Department of Entomology
University of Kentucky
S-225 Ag Science North
Lexington, KY 40546-0091
Article provided by Equine Disese Quarterly