Ehrlichiosis in Dogs

Ehrlichiosis is a disease that primarily affects blood cells. It is caused by bacteria that are spread by ticks. This disease was first discovered in the United States in the 1970s and increased in frequency throughout the 1980s and 1990s. 

According to the Companion Animal Parasite Council, nearly 3 percent of dogs within the United States tested positive for ehrlichiosis in 2022 (1).

What is Ehrlichiosis?

Ehrlichiosis is a bacterial infection that can be caused by several different Ehrlichia species. The species most commonly involved in canine ehrlichiosis are Ehrlichia canis and Ehrlichia ewingii. 

Both of these bacteria are also capable of causing human infection, although humans are most commonly infected with a different Ehrlichia species. It is important to note, however, that humans cannot get this tick-borne disease directly from an infected dog. Infection can only occur through the bite of an infected tick.

Ehrlichiosis is a disease that is seen worldwide. Within the United States, ehrlichiosis is most common in the Southwest and Southeast. 

Any breed of dog can be infected with ehrlichiosis. German Shepherds appear to be more susceptible to this infection than other breeds, but the cause of this predisposition is unknown.

What Causes Ehrlichiosis in Dogs?

Ehrlichiosis is spread through the bite of an infected tick.

When tick larvae hatch out of their eggs, they immediately begin to search for an animal to feed on. If they feed on a dog or a wild animal with ehrlichiosis, that tick becomes infected with bacteria. This infection will persist within the tick as the tick continues to mature to adulthood, resulting in the tick spreading the infection to any human or animal that it feeds upon.

Once the bacteria have entered a dog through a tick bite, the bacteria replicate and spread throughout the dog’s bloodstream.  

Which Ticks Transmit Ehrlichiosis to Dogs?

The most common cause of ehrlichiosis, Ehrlichia canis, is typically spread by the Brown Dog Tick. 

Ehrlichia ewingii, a less common cause of ehrlichiosis, is primarily spread by the bite of the Lone Star Tick. 

Other tick species may spread other strains of ehrlichiosis, but these are far less likely to infect dogs.

Ehrlichia Symptoms in Dogs

The most significant symptoms of ehrlichiosis are seen in dogs that are infected with Ehrlichia canis. These dogs tend to go through a set progression of clinical signs. 

In the acute phase of infection, which occurs 1-3 weeks after the bite of an infected tick, dogs may develop signs such as fever, weight loss, and trouble breathing. This sudden illness may be mild and dismissed by pet parents, or it may be severe enough to warrant seeking veterinary care. After a few weeks, signs of illness typically resolve. 

Dogs then enter a stage that is referred to as subclinical infection. Dogs typically have no visible signs of illness during the subclinical phase, although they may have difficulties with blood clotting if they become injured. In some cases, the condition continues to progress and dogs develop clinical ehrlichiosis. In this phase, signs may include bleeding disorders, limping, and other issues. 

Dogs infected with Ehrlichia ewingii, the less common form of ehrlichiosis, develop different clinical signs. These dogs may develop fever, lethargy, limping, gastrointestinal signs, and neurologic signs. 

Ehrlichiosis symptoms in dogs may include any of the following:

• Fever
• Lethargy
• Dehydration
• Weight loss
• Breathing difficulties
• Enlarged lymph nodes
• Limping
• Bleeding disorders (nosebleeds, coughing up blood, unexplained bruises)
• Pale gums
• Vomiting or diarrhea
• Neurologic signs (difficulty walking, muscle tremors, seizures, loss of consciousness)

Diagnosing This Condition in Dogs

If your dog has nonspecific signs of illness, such as those seen with ehrlichiosis, your veterinarian will likely begin by performing blood tests. A complete blood cell count and serum biochemistry allow your veterinarian to assess your dog’s overall health, including red blood cell count, white blood cell count, platelet count, and organ function tests. If your dog has ehrlichiosis, these blood tests typically show an abnormally low platelet count and low blood protein levels. Red blood cell counts and white blood cell counts may also be reduced.

The most common test for ehrlichiosis is an in-house test that detects Ehrlichia canis. This test can be run in the veterinary clinic and provides accurate results in approximately 10 minutes. In-house testing may be performed on dogs with suspected ehrlichiosis, but it is also often performed as a part of yearly wellness testing in dogs. Many heartworm tests used by veterinary clinics also include a test for Ehrlichia canis.

Other tests are available to detect less-common Ehrlichia species. These tests often require sending a blood sample to an off-site laboratory for analysis. It may take several days to receive the results from these tests. 

How to Treat Ehrlichiosis in Dogs

Ehrlichiosis is a bacterial infection. Therefore, the most important component of ehrlichiosis treatment in dogs is antibiotics. 

Dogs that are severely ill may require additional treatments. In some cases, medication may be required to address pain and inflammation. Dogs with significant bleeding problems may need to be hospitalized for blood transfusions, to address anemia and low cell counts. 

Medications to Treat Ehrlichiosis in Dogs

Doxycycline is an oral antibiotic used to treat ehrlichiosis. This antibiotic is used to treat a variety of tick diseases. Doxycycline may be given in tablet or capsule form. Treatment with doxycycline is typically continued for four weeks, in order to fully eliminate the infection. The most common side effects of doxycycline are nausea and vomiting. Giving the medication with food may lessen side effects. In some cases, other antibiotics that are closely related to doxycycline, such as minocycline or tetracycline, may be used. 

Prednisone tablets may also be given in severe cases, to reduce inflammation associated with ehrlichiosis. Side effects of prednisone may include increased thirst and urination, increased appetite, and increased panting. These side effects typically resolve once the medication is stopped.

General Cost to Treat Canine Ehrlichiosis

The cost of ehrlichiosis treatment depends on the severity of the disease. In dogs with mild disease, requiring only doxycycline, the cost of medication may range from $25-$100. 

In dogs with severe signs of disease, requiring blood transfusions and more aggressive treatment, the cost may increase to thousands of dollars.

How to Prevent Dogs From Contracting Ehrlichiosis

The only way to prevent ehrlichiosis is to ensure that your dog is not exposed to ticks. For most dogs, this requires the use of year-round tick prevention. There are a number of different types of tick prevention available, including oral medications, topical medications, and tick collars. Tick prevention not only prevents ehrlichiosis, but also prevents other tick borne diseases in dogs. 

Talk to your veterinarian to determine the best tick prevention for your pet. 

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