What Causes Ehrlichiosis?

Ehrlichiosis is caused by a bacteria called Ehrlichia, which is spread to dogs through the bite of a tick. Brown dog ticks are the most common tick to spread Ehrlichiosis, although it has been spread by the lone star tick, deer tick, and American dog tick. All dog breeds can be infected with Ehrlichia but not every infected dog will become seriously ill from the disease.

Symptoms of Ehrlichiosis in Dogs

The bacteria infects white blood cells and causes a variety of symptoms. Symptoms are generally seen 1-4 weeks after the tick bite. The disease has three stages: acute, subclinical, and chronic. Some dogs that are infected never become sick, while for other dogs, the infection can be fatal. Dogs may progress through only some or all of the stages of the disease. It is unknown why some dogs become severely ill and others are mildly affected.

What you see in the acute stage: This stage most commonly occurs 1-4 weeks after the tick bite. Some dogs clear the infection during this stage, while others progress to further stages.

• Fever
• Lethargy
• Anorexia
• Lameness - often as a stiff gait
• Swollen lymph nodes
• Weight loss
• Vomiting and diarrhea
• Bleeding disorders - pale gums, bruising, nosebleeds
• Neurologic abnormalities - head tilt, abnormal gait, seizures
• Blood cell abnormalities

What you see in the subclinical stage: Dogs can be in the subclinical stage for months to years. From here they may clear the infection, progress to the chronic stage, or remain in the subclinical stage and carry the bacteria throughout their life.

• The dog has no outward signs of the disease
• Some dogs have a mild low platelet count

What you see in the chronic stage: This stage can occur months to years after the initial infection. Any breed can progress to the chronic stage, but it is more commonly seen in German Shepherd dogs, Siberian Huskies, and Belgian Malinois. Signs are similar to the acute stage but are often more severe and can depend on what organ(s) are affected.

• Fever
• Lethargy
• Anorexia
• Weight loss
• Lameness - often as a stiff gait
• Swollen lymph nodes
• Systemic disease - kidney failure, liver disease, pneumonia
• Bleeding disorders - pale gums, bruising, nosebleeds
• Neurologic abnormalities - head tilt, abnormal gait, seizures
• Blood cell abnormalities

Diagnosing Ehrlichiosis in Dogs

Diagnosing Ehrlichiosis can be tricky because some dogs may test positive for years after exposure to the bacteria. Therefore, a positive result may show that they were exposed to Ehrlichia at some point but might not have an active infection. Along with testing for the organism, we often look for clinical signs and corresponding bloodwork abnormalities to make a definitive diagnosis. There are many different ways to diagnose Ehrlichiosis.

Most veterinarians can test for Ehrlichia in the clinic. A blood sample can determine if your pet has antibodies to Ehrlichia. Antibodies are proteins that our bodies make to defend against infection. This test lets us know if your pet has been exposed to the bacteria, but it does not tell you if they have a current infection. If your pet is showing clinical signs of Ehrlichiosis and they test positive in the veterinary clinic, further testing is necessary to determine if the results are indicating an active infection.

Outside lab testing can identify the type and quantity of antibodies. This helps determine if your pet has an active infection. It may be necessary to run two tests, a few weeks apart, to see how the antibody level is changing. If the antibody numbers are increasing, it is likely an active infection. If the antibody numbers remain the same or are decreasing it is likely not an active infection.

PCR tests are also available for Ehrlichia. This tests for the presence of the bacteria’s genetic material. If your pet is positive on a PCR test, it indicates that they are likely actively infected with Ehrlichia bacteria.

Treating Ehrlichia in Dogs

Ehrlichia is treated with tetracycline antibiotics, most commonly, Doxycycline. Dogs are normally treated with antibiotics for 4 weeks or longer. If the patient has severe symptoms, other medications and even 24-hour hospitalization may be needed.

Preventing Ehrlichiosis in Dogs

As Ehrlichia is transmitted by a tick bite, we can try to prevent this disease by reducing exposure to ticks. There are many medications available that help prevent tick bites. Some are applied as a topical medication on the skin, while others are given as a chewable treat. Many of these medications last for one month. Giving these medications year-round is important, as even in cold climates, ticks will emerge with just a few warm days, and it is hard to gauge when ticks will return in the spring.

​​Can people get Ehrlichiosis?

People can be infected with Ehrlichia, but dogs cannot spread the disease to humans. The bacteria needs to be transmitted by the bite of a tick. However, if your dog tests positive for Ehrlichia, it tells you that the ticks in your area are likely carrying the bacteria.

Make sure to regularly check for ticks on your pets and everyone in your family. Contact your doctor if you have been bitten by a tick or have any symptoms after a tick bite.

Read more:

Rocky Mountain Spotted Fever in Dogs

Symptoms and Treatment of Babesiosis in Dogs

Lyme Disease in Dogs

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