What is Tularemia?
This disease occurs throughout the Northern Hemisphere and has been reported in North America, China, Japan, and Korea. Tularemia is a notifiable disease in the United States and is a zoonotic disease, which means it can be transmitted from animals to humans. In humans, the symptoms may be similar to that of the common cold, with symptoms commonly including lethargy, chills and headache. If your suspect that your horse may have Tularemia you should contact both your doctor and the veterinarian.
Tularemia is bacterial disease that affects horses and other mammals such as rabbits, hares, and rodents. This disease is caused by the bacteria Francisella tularensis and is transmitted by biting insects such as ticks, lice, mosquitoes and horseflies. Although rare, it can be seen in horses. Tularemia in horses is often accompanied by severe tick infestations, fever, shortness of breath, ataxia, and depression.
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Symptoms of Tularemia in Horses
The symptoms may vary, with some animals showing no signs of the disease. When symptoms are seen these may include:
- Severe tick infestations
- Weak or wobbling knees
- Vomiting (though not in horses)
- Swelling of the lower limbs
In rabbits or rodents that develop this disease, they may huddle together and behave strangely.
Causes of Tularemia in Horses
This disease is highly infectious and caused by the bacteria Francisella tularensis. This bacterium can live in the soil, water and vegetation for months and can be spread through infected biting insects, through the air or through direct contact with contaminated water or environments. Carnivorous animals such as prairie dogs may contract this disease by eating the flesh of an infected animal. Tularemia is most commonly spread to horses through tick infestation.
Diagnosis of Tularemia in Horses
The first thing your veterinarian will do is perform a thorough physical examination. Your vet will ask questions and discuss your horse’s history with you. They will then watch your horse from a distance to observe their gait and movement, behavior and body condition. Your vet will then carefully examine your horse, monitoring heart and respiration rates and thoroughly checking over their body. Further diagnostic tests your veterinarian may perform are:
Serology, Antibody Titer
This diagnostic test is performed by sending a blood sample to a laboratory. This tests for antibodies in the blood that show exposure to the antigen (disease). High titer levels of the antibody may lead to a diagnosis of the disease.
Complete Blood Count
This is a diagnostic test that is performed using a blood sample collected from the vein. The number of red and white blood cells and platelets are then counted. This can indicate infection, inflammation, dehydration, and anemia, among other conditions.
Culture and Sensitivity
This test is used to test for bacteria present on your horse. Your veterinarian will take a sample using a sterile cotton culture swab. This sample will then be sent to a laboratory for testing. At the laboratory this sample is spread onto a bacterial growth medium and watched for growth patterns and characteristics that indicate bacterium type. A “sensitivity” is determined by introducing antibiotics into the bacteria colony, bacteria death indicates effectiveness.
Treatment of Tularemia in Horses
If your horse receives prompt antibiotic treatment the chance of recovery is greatly improved. Streptomycin, an aminoglycoside antibiotic, will most likely be used for your horse. This is the drug of choice for both animals and humans. Your horse will require a 14 day course.
Recovery of Tularemia in Horses
Parasite control is essential to decrease the risk of your horse developing this condition. Ensure an effective parasite control program is in place, your veterinarian can help implement an appropriate regime for your horse.
Prevent exposure to rodents and rabbits as they are carriers of the disease. Manage your facilities well to decrease the rodent population and ensure the environment is free of brush piles. To prevent attracting rodents, store all grain and food in sealed containers. Use humane rat traps. Other steps you can take are:
- Ensure your horse’s fresh fruit and vegetables are thoroughly washed prior to consumption
- Enable access to clean, fresh drinking water only
- Avoid contact with sick animals – quarantine any unwell animals
As tularemia is a zoonotic disease consider your own well-being and prevention as well as your horses. Ensure that you:
- Wash all fruits and vegetables prior to consumption
- Avoid contact with wild animals, avoid handling dead wildlife without using gloves and appropriate protective gear
- Wash your hands thoroughly with a chlorhexidine wash following contact with animals
- Avoid contact where possible with sick animals
- Ensure all food is cooked thoroughly and well heated.
- Only drink water from a safe, clean source
Tularemia is a notifiable disease in the United States, if your horse is diagnosed with this disease this should be reported to local or state health authorities.