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Tularemia in horses is a rare bacterial infection caused by Francisella tularensis, an organism most often associated with rabbits, rodents, ticks, biting flies, and contaminated environmental sources.
Although reported cases in horses are uncommon, tularemia can cause serious systemic illness when infection occurs. Signs such as fever, lethargy, reduced appetite, weight loss, and enlarged lymph nodes can resemble many other infectious diseases, making veterinary evaluation and diagnostic testing important.
Tularemia is also a zoonotic disease, meaning it can affect humans as well as animals. Horse owners in areas where tularemia occurs should be aware of potential exposure risks, especially during seasons when ticks and biting insects are active or when wildlife activity around barns and pastures is high.
Understanding the risks associated with tick exposure is important for all horse owners in endemic regions. Keep reading to learn more about tularemia and how to reduce risk to keep your herd safe during peak insect and tick seasons.
What is Tularemia in Horses?
Tularemia is a bacterial disease that affects a wide range of mammals, birds, and reptiles. Also known as rabbit fever, the disease is caused by Francisella tularensis bacteria.
Infection is most often spread through tick and deer fly bites, contact with infected animals, or exposure to contaminated food, water, or soil. [1]
Tularemia occurs throughout much of the Northern Hemisphere, including North America, Europe, and parts of Asia. Although the disease is widely distributed, reported cases in horses are rare.
Horses appear less prone to infection than many other animal species, and relatively few equine cases have been described in the veterinary literature. However, tularemia can cause serious illness when infection does occur. [2][3][4]
Because the disease is uncommon and many of its symptoms overlap with those of other infectious conditions, horse owners may have difficulty recognizing tularemia based on clinical signs alone.
Early veterinary evaluation and diagnostic testing are important for horses showing signs of illness, particularly in regions where tularemia is known to occur and during periods of increased tick and insect activity.
Although tularemia is uncommon in horses, infections can occur when animals are exposed to infected ticks, biting flies, wildlife, or contaminated environmental sources. Most reported equine cases have occurred in regions where the disease is already established in local wildlife populations. [1][5][6]
Once inside the body, F. tularensis can spread through the lymphatic system and bloodstream, triggering inflammation and systemic illness. The severity of infection varies among species and individuals.
Horses appear less susceptible to tularemia than many other animals, which may help explain why equine cases are reported relatively infrequently. [2][7]
Tularemia is a zoonotic disease, meaning it can infect humans. People are most commonly exposed through tick bites, contact with infected wildlife, or contaminated environmental sources.
Because tularemia can also affect humans, horse owners and veterinary professionals should use appropriate precautions when handling animals suspected of having the disease. [1]
Understanding how horses are exposed to F. tularensis can help owners recognize risk factors and take steps to reduce the likelihood of infection.
What's your top priority with your horse's health?
What's your top priority with your horse's health?
Is Tularemia Contagious?
Tularemia is not generally considered contagious between horses. Most infections occur when horses are exposed to infected ticks, biting flies, wildlife, or contaminated environmental sources rather than through direct contact with another horse.
Although horse-to-horse transmission appears uncommon, veterinarians may recommend limiting unnecessary contact with affected animals until a diagnosis is confirmed and appropriate biosecurity measures are in place.
Table 1. Tularemia in Horses at-a-glance
| Category | Key Information |
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| Definition |
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| Primary Cause |
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| Common Causes |
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| Onset |
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| Symptoms |
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| Severity |
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| Treatment |
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| Recovery Time |
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| Prognosis |
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| Prevention |
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Causes
Tularemia is caused by infection with the bacterium Francisella tularensis. This organism is adapted to live in the bodies of host mammals. Wildlife populations are the primary hosts, particularly rabbits, rodents, and other small animals.
Horses can become infected when they are exposed to the bacteria through insect vectors, infected animals, or contaminated environmental sources. [1][5][8]
Tick Bites
Ticks are considered one of the primary vectors of F. tularensis. Horses may become infected when an infected tick feeds on them and transmits the bacteria through its saliva. Ticks typically acquire the organism while feeding on infected wildlife then spread it to other animals. [9]
Safe Tick Removal
Ticks should be removed as soon as they are found, using a slow and careful technique to limit skin irritation and reduce the risk of pathogen transmission. Wear gloves if possible, and use fine-tipped tweezers or a tick-removal tool to grasp the tick.
Apply steady upward pressure and allow the tick to release from the skin without twisting, jerking, or crushing it. The tick may remain attached for several seconds before letting go, so maintain gentle, even pressure rather than pulling abruptly. Avoid squeezing the tick’s body, as this may push infectious material into the bite site.
Once the tick is removed, clean the area with an appropriate antiseptic and continue monitoring the skin for swelling, irritation, discharge, or other signs of infection.
Do not try to remove ticks by burning them, smothering them with petroleum jelly, or applying chemicals to force detachment. These methods can increase the risk of injury or disease transmission.
Contact your veterinarian if mouthparts remain in the skin, the bite becomes inflamed, or the horse develops signs such as fever, swelling, lameness, or lethargy after a tick bite.
Biting Flies
Biting insects, particularly deer flies or horse flies, can also transmit tularemia. These insects may carry the bacteria from infected animals and introduce it to new hosts during feeding. [1][10]
The risk of exposure is generally highest during the warmer months when fly activity peaks. Horses kept near wooded areas, wetlands, brush, or wildlife habitat may be more likely to encounter infected biting insects, especially if deer flies or horse flies are active on the property.
Fly control, turnout management, and reducing exposure during periods of heavy biting insect activity can help lower the risk of insect-borne transmission. Because tularemia can also affect people, owners should take care when handling sick animals, carcasses, or heavily contaminated environments.
Contact with Infected Wildlife
Rabbits and rodents are among the most important reservoirs of F. tularensis. Horses may risk exposure through direct contact with infected animals, carcasses, or materials contaminated by wildlife. While this route of transmission is considered less common than insect-borne exposure, it may contribute to infection in some cases. [1][10]
Wildlife exposure may occur when horses share environments with infected animals or when contaminated carcasses, water sources, or pasture spaces are present. Barn cats, dogs, or other animals may also move carcasses or wildlife remains into areas used by horses and people.
Owners should avoid handling dead wildlife with bare hands and should remove carcasses from horse areas using appropriate protective equipment. Maintaining property hygiene, secure feed storage, rodent control, and prompt removal of animal remains can help reduce potential exposure to wildlife-associated sources of infection.
Contaminated Water & Environmental Sources
F. tularensis can survive in water, soil, mud, and other moist environments for extended periods. Horses may become infected by consuming contaminated water or feed, or through contact with environmental sources containing the bacteria.
Risk Factors
Several environmental and management factors may increase a horse’s risk of exposure to Francisella tularensis, including: [10]
- Living in regions where tularemia is endemic
- Exposure to ticks or biting flies
- Grazing in areas with large rabbit or rodent populations
- Access to untreated ponds, streams, or other natural water sources
- Spending time in wooded, brushy, or heavily vegetated pastures
- Increased insect activity during the spring, summer, and early fall
Horses with one or more of these risk factors are not necessarily more susceptible to infection, but they may have a greater likelihood of encountering the bacteria in their environment.
Clinical Signs
Clinical signs of tularemia in horses are not well-characterized because naturally occurring cases are uncommon. Reported symptoms are generally nonspecific and may resemble those associated with many other bacterial, viral, or tick-borne diseases.
Affected horses may develop: [2][8][11]
- Fever
- Lethargy
- Reduced appetite (anorexia)
- Weight loss
- Enlarged lymph nodes
- Lack of coordination (ataxia)
- Breathing difficulties
In many cases, fever, decreased appetite, and lethargy are among the earliest signs noticed by owners, beyond horses appearing generally unwell. Enlargement of nearby lymph nodes may occur as the immune system responds to infection.
Additional signs may occur depending on the severity and progression of infection. While some horses may experience relatively mild disease, others can develop more severe systemic illness requiring veterinary care.
Because these clinical signs are not unique to tularemia, diagnostic testing is required to distinguish this disease from other conditions that cause fever, lethargy, weight loss, and enlarged lymph nodes in horses.
When to Contact a Veterinarian
Horse owners should contact a veterinarian whenever a horse becomes suddenly unwell after possible exposure to ticks, biting insects, wildlife, or contaminated environments. Because tularemia is uncommon in horses and its signs are nonspecific, veterinary assessment is important to rule out other infectious, inflammatory, neurologic, or tick-borne diseases that can appear similar.
Call your veterinarian promptly if your horse develops a persistent fever, stops eating, becomes unusually dull, shows swollen lymph nodes, or appears uncoordinated or weak. Breathing difficulty, rapid decline, or signs affecting multiple body systems should be treated as urgent concerns.
Veterinary evaluation is also warranted if illness occurs after known tick attachment, heavy deer fly or horse fly exposure, contact with rabbits or rodents, or discovery of sick or dead wildlife on the property. These history details can help your veterinarian determine whether tularemia or another infectious disease should be considered.
Diagnosis
Because the clinical signs of tularemia overlap with those of many other diseases, diagnosis typically requires laboratory testing. Veterinarians often begin by evaluating the horse’s clinical signs, medical history, and potential exposure to ticks, biting insects, wildlife, or contaminated environments.
During a physical examination, a veterinarian may identify findings such as fever, enlarged lymph nodes, lethargy, or other signs of systemic illness. However, these findings are not specific to tularemia and cannot confirm a diagnosis.
Blood tests may reveal abnormalities consistent with infection or inflammation, but additional testing is required to identify Francisella tularensis specifically.
Diagnostic tests for Francisella tularensis may include: [12][13]
- Serology to detect antibodies against F. tularensis
- Polymerase chain reaction (PCR) testing to identify bacterial DNA
- Culture of infected tissues or body fluids
Because F. tularensis can pose a risk to laboratory personnel, bacterial culture requires specialized handling procedures and is not routinely performed in all laboratories.
Differential Diagnosis
Several conditions can cause signs that resemble tularemia in horses, including:
- Strangles
- Potomac horse fever
- Equine anaplasmosis (formerly erlichiosis)
- Equine infectious anemia
- Other bacterial or viral infections that cause fever and enlarged lymph nodes
Accurate diagnosis is important because treatment recommendations and biosecurity considerations may differ depending on the underlying cause of illness.
Treatment
Prompt treatment is important for horses diagnosed with tularemia. Because the disease is caused by a bacterial infection, treatment typically involves antimicrobial therapy along with supportive care to address clinical signs and maintain hydration and comfort.
Antibiotic Therapy
Several antibiotics have been used to treat tularemia in animals. The choice of medication, dosage, and treatment duration depends on factors such as the severity of illness, the horse’s overall health, and the veterinarian’s clinical judgment. [8]
Early treatment may improve the likelihood of a successful outcome and help reduce the risk of complications associated with systemic infection.
Supportive Care
In addition to antibiotics, your veterinarian may recommend supportive care to help affected horses recover. Depending on the severity of disease, supportive treatments may include:
- Fluid therapy to maintain hydration
- Anti-inflammatory medications to reduce fever and discomfort
- Nutritional support for horses with reduced appetite
- Rest and monitoring during recovery
Horses with severe illness or complications requiring intensive veterinary management may additionally require hospitalization.
Monitoring Recovery
Regular veterinary follow-up can help assess the horse’s response to treatment and identify any ongoing health concerns. Improvements in appetite, attitude, body temperature, overall condition, and other factors are often used to evaluate recovery.
Prognosis
Because tularemia is uncommon in horses, information regarding long-term outcomes is limited. However, horses that receive prompt veterinary care generally have a better prognosis than those with delayed diagnosis and treatment. [8]
The prognosis for horses with tularemia depends on several factors, including the severity of infection, how quickly the disease is recognized, and how soon treatment is initiated.
Severe systemic infections may require intensive supportive care and prolonged recovery periods. As with many infectious diseases, early intervention can help reduce the risk of complications and improve the likelihood of a successful outcome.
Prevention
Preventing tularemia in horses involves reducing exposure to infected ticks, biting insects, wildlife, and contaminated environmental sources. Although tularemia is uncommon in horses, owners in areas where the disease occurs can take steps to reduce the risk of infection.
Control Ticks & Biting Insects
Ticks and biting flies are important carriers of Francisella tularensis. An effective insect control program can help reduce exposure to tularemia and other vector-borne diseases. [8]
Preventive measures include:
- Using veterinarian-approved fly and tick control products
- Regularly checking horses for ticks and removing them promptly
- Mowing tall grass and managing brush around pastures
- Using fly masks, fly sheets, and other protective gear when appropriate
- Reducing standing water and other insect breeding areas
Limit Contact with Wildlife
Rabbits, rodents, and other small mammals can carry F. tularensis without appearing sick. Reducing contact between horses and wildlife may help lower the risk of exposure.
To limit contact with wildlife, horse owners can:
- Store feed in sealed containers
- Clean up spilled grain and feed
- Implement rodent control measures around barns
- Remove wildlife attractants when possible
- Avoid handling wildlife carcasses without protective equipment
Maintain Clean Water Sources
The bacteria that cause tularemia can survive in water and other moist environments. Providing clean drinking water and limiting access to potentially contaminated sources can help reduce exposure.
Best practices to maintain clean water sources include:
- Providing fresh, clean water daily
- Inspecting ponds and water troughs regularly
- Preventing wildlife access to feed and water sources whenever possible
Practice Good Biosecurity
Tularemia is a zoonotic disease that can affect both animals and humans. Although evidence of horse-to-human transmission is limited, horse owners should take appropriate precautions when caring for horses suspected of having the disease. [11][15][16][17]
Recommended biosecurity measures include:
- Contacting a veterinarian promptly if tularemia is suspected
- Limiting unnecessary handling of affected horses until a diagnosis is confirmed
- Wearing disposable gloves when handling sick animals, bodily fluids, or potentially contaminated materials
- Washing hands thoroughly after animal contact
- Avoiding direct contact with wildlife carcasses or tissues
- Cleaning and disinfecting equipment that has come into contact with sick horses
- Following veterinary recommendations regarding isolation and disease management
People who develop fever, swollen lymph nodes, skin lesions, or flu-like symptoms after exposure to a horse or wildlife suspected of having tularemia should seek medical attention and inform their healthcare provider about the potential exposure. Early diagnosis is important because tularemia can also affect humans.
Frequently Asked Questions
Here are some frequently asked questions about tularemia in horses:
Tularemia in horses is an uncommon bacterial infection caused by Francisella tularensis. This disease is also known as rabbit fever because rabbits, rodents, and other small mammals are important natural reservoirs for the bacteria. Although horses appear less susceptible than many other species, tularemia can cause serious systemic illness when infection occurs. Veterinary diagnosis and treatment are important because the signs can resemble many other infectious diseases.
Horses get tularemia when they are exposed to Francisella tularensis through infected insects, wildlife, or contaminated environments. Tick bites are considered an important route of transmission, and biting flies such as deer flies or horse flies may also spread the bacteria. Horses may also be exposed through contact with infected rabbits, rodents, carcasses, contaminated feed, contaminated water, soil, mud, or other moist environmental sources. Risk is generally higher in areas where tularemia is established in local wildlife populations.
Signs of tularemia in horses are usually nonspecific and can include fever, lethargy, reduced appetite, weight loss, and enlarged lymph nodes. Some affected horses may also show lack of coordination or breathing difficulties, depending on the severity and progression of infection. Because these signs overlap with many bacterial, viral, and tick-borne diseases, they cannot confirm tularemia on their own. A veterinarian should evaluate horses with fever, depression, swollen lymph nodes, or other signs of systemic illness.
Tularemia is not generally considered contagious between horses. Most infections occur after exposure to infected ticks, biting flies, wildlife, contaminated water, contaminated feed, or environmental sources rather than direct horse-to-horse spread. Even so, veterinarians may recommend limiting unnecessary contact with a sick horse until the cause of illness is confirmed. Basic biosecurity precautions are especially important because tularemia can also affect humans.
Humans can get tularemia, but horse-to-human transmission is poorly documented. People are more commonly exposed through tick bites, contact with infected wildlife, or contaminated environmental sources. Horse owners should still use caution when handling sick horses, body fluids, bedding, equipment, or materials that may be contaminated. Anyone who develops fever, swollen lymph nodes, skin lesions, or flu-like symptoms after possible exposure should seek medical care and mention the potential tularemia exposure.
Tularemia in horses is diagnosed by combining clinical signs, exposure history, physical examination findings, and laboratory testing. A veterinarian may consider tularemia when a horse has fever, lethargy, enlarged lymph nodes, and a history of exposure to ticks, biting insects, wildlife, or contaminated environments. Diagnostic testing may include serology to detect antibodies, polymerase chain reaction testing to identify Francisella tularensis genetic material, or bacterial culture from infected tissues or fluids. Culture requires specialized handling because Francisella tularensis can pose a risk to laboratory personnel.
Diseases that can look like tularemia in horses include strangles, Potomac horse fever, equine ehrlichiosis, equine anaplasmosis, equine infectious anemia, and other infections that cause fever or enlarged lymph nodes. These conditions can produce similar early signs, such as lethargy, reduced appetite, and general illness. This is why diagnostic testing is needed instead of relying on symptoms alone. Correct diagnosis matters because treatment, monitoring, and biosecurity recommendations may differ depending on the underlying disease.
Tularemia in horses is treated with veterinary-directed antimicrobial therapy and supportive care. The choice of medication, dose, and treatment duration depends on the horse's condition, severity of illness, and the veterinarian's clinical judgment. Supportive care may include fluid therapy, anti-inflammatory medication, nutritional support, rest, and close monitoring during recovery. Severely affected horses may require hospitalization or more intensive veterinary management.
You should call a veterinarian about possible tularemia if your horse develops fever, lethargy, reduced appetite, weight loss, enlarged lymph nodes, or other signs of systemic illness after possible exposure to ticks, biting insects, wildlife, or contaminated environments. Prompt veterinary evaluation is important because tularemia is uncommon and cannot be reliably identified from symptoms alone. Early diagnosis and treatment may improve the chance of recovery and reduce the risk of complications. Veterinary advice is also recommended if multiple animals become ill or if unusual numbers of sick or dead rabbits, rodents, or other wildlife are found nearby.
Animals that carry tularemia most commonly include rabbits, rodents, and other small mammals. These wildlife species can serve as natural reservoirs for Francisella tularensis and may contaminate the environment or infect insects that later feed on horses. Ticks and biting flies can also carry and transmit the bacteria after contact with infected animals. Reducing contact with wildlife and controlling insect vectors can help lower exposure risk for horses.
Tularemia is found throughout much of the Northern Hemisphere, including North America, Europe, and parts of Asia. The disease is more relevant in regions where Francisella tularensis is established in wildlife populations. Horses living in wooded, brushy, heavily vegetated areas or places with high tick, biting fly, rabbit, or rodent activity may have greater exposure risk. Seasonal insect activity in spring, summer, and early fall can also increase the likelihood of contact with infected vectors.
Tularemia prevention in horses focuses on reducing exposure to ticks, biting flies, wildlife, and contaminated water or feed. Practical steps include using veterinarian-approved fly and tick control, checking horses for ticks, mowing tall grass, managing brush, reducing standing water, and using protective gear such as fly masks or fly sheets when appropriate. Feed should be stored in sealed containers, spilled grain should be cleaned up, and rodent control should be maintained around barns. Providing fresh, clean drinking water and limiting wildlife access to feed and water sources can also help reduce risk.
There is no commercially available tularemia vaccine for horses. Prevention relies on management practices that reduce exposure to infected insects, wildlife reservoirs, and contaminated environments. Horse owners in areas where tularemia occurs should focus on tick control, biting fly control, clean water, wildlife management, and prompt veterinary attention for unexplained illness. These measures are especially important during periods of increased tick and insect activity.
Tularemia can be serious in horses, but the prognosis depends on the severity of infection and how quickly treatment begins. Because equine cases are rare, long-term outcome information is limited. Horses that receive prompt veterinary diagnosis, antimicrobial therapy, and supportive care are expected to have a better chance of recovery than horses with delayed treatment. Severe systemic infections may require intensive care and a longer recovery period.
Summary
Tularemia is a rare bacterial disease caused by Francisella tularensis that can affect horses, wildlife, and humans.
- Horses typically become infected through exposure to infected ticks, biting flies, wildlife, or contaminated environmental sources
- Clinical signs include fever, lethargy, reduced appetite, weight loss, and enlarged lymph nodes
- Because the symptoms are nonspecific, laboratory testing is required to confirm a diagnosis
- Treatment typically involves antibiotics and supportive care, with earlier intervention generally associated with better outcomes
- Prevention focuses on insect control, wildlife management, clean water sources, and appropriate biosecurity practices
References
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