Ehrlichiosis In Dogs: When To Worry


When it comes to ticks, Lyme disease is the buzzword.  

But did you know there are several other diseases that your dog can get from tick bites?

A big one you may not have heard about is ehrlichiosis.

… And it can cause fever, muscle pain, lethargy and long-term side effects.  

Like Lyme, ehrlichiosis can sound scary when you first hear what it is.

But you shouldn’t treat ehrlichiosis just because your dog tests positive for it.

In fact, you shouldn’t worry about ehrlichiosis tests at all … unless there are other factors present.

I’ll talk more about this shortly.

But before that, let’s look at what ehrlichiosis is and how to identify it.

What is Ehrlichiosis?

Dogs get ehrlichiosis when infected by Ehrlichia bacteria through a tick bite. This bacterium is most often carried by:

  • Lone Star ticks
  • Brown Dog ticks
  • Black-legged ticks

It’s most prominent in the southeastern and south-central United States.

Signs that your dog has ehrlichiosis are:

  • Fever
  • Swollen lymph nodes
  • Depression
  • Lethargy
  • Respiratory distress
  • Muscle and joint pain
  • Weight loss

In some cases, ehrlichiosis can lead to severe issues like:

  • Neurological symptoms
  • Bleeding disorders

But before you jump to fear-based conclusions at the first sign of a tick there’s something you must know …

Like Lyme disease, your dog can have ehrlichiosis without any problems.

When To Treat You Dog For Ehrlichiosis

Synbiotics published a summary about tick-borne disease treatment and tests in dogs.

Vets should diagnose based on a combination of …

  • Clinical signs
  • Hematological abnormalities
  • Serology findings (a titer test for antibodies)

They shouldn’t base the diagnosis on serology alone.

“When clinical signs or clinicopathologic abnormalities consistent with ehrlichiosis are found in conjunction with positive ehrlichial serology … a clinical diagnosis of ehrlichiosis should be made and treatment instituted.” Journal of Veterinary Internal Medicine (JVIM)

Look at Lyme as an example.

Dr Thomas Rau tested high-risk farmers for Lyme. 80% of the farmers tested positive for Lyme disease but …

… only 2% showed any symptoms.

This is because most were able to fight off the disease on their own.

Should You Test Your Dog For Ehrlichiosis?

The JVIM talks about the reasons for and against serological tests.

Arguments For Serological Tests

To screen for ehrlichial antibodies in otherwise healthy dogs:

  1. Gives more information about the level of ehrlichiosis in dogs.
  2. Identifies where to find ehrlichiosis infected ticks.
  3. Allows dogs to act as an indicator for the risk of ehrlichiosis in humans.
  4. May reduce the development of ehrlichiosis in kennels.
  5. Could detect subclinically infected dogs and promote more effective therapy.
  6. Could reduce the population of infected animals with treatment for infected dogs.

Arguments Against Serological Tests

There are even more arguments not to screen healthy dogs for ehrlichial antibodies.

  1. False-positive tests could result in avoidable treatment of dogs who are not infected.
  2. Current serological tests (Snap 3Dx) only detect the Ehrlichia canis antigen. It can’t detect other ehrlichial species like …
    Ehrlichia platys
    Ehrlichia risticii var. atypicalis
    Ehrlichia ewingii
    Ehrlichia chaffeensis
    Ehrlichia phagocytophilia
    Ehrlichia equi
    Human Granulocytic Ehrlichia (HGE)
  3. There is no proof that treatment of ehrlichiosis prevents chronic side effects.
  4. Dogs with a strong immune system may be able to fight the infection without treatment.
  5. The rate at which dogs can fight infection without treatment is not known.
  6. There’s no way to know which dogs will develop chronic disease manifestations.
  7. The presence of ehrlichial antibodies does not mean there is a current infection. It only means the dog’s had exposure to the bacteria.

    The Journal of Veterinary Internal Medicine notes that …

    “After successful treatment in most dogs, antibody titers decline and generally become negative within 6-9 months … Some dogs have a resolution of clinical and clinicopathologic abnormalities yet retain high titers to E. canis for years. It can’t always be determined in these dogs whether there’s continued infection or merely persistence of antibodies.”

  8. There is no treatment benefit for healthy dogs. Dogs treated for ehrlichiosis don’t develop permanent immunity. Reinfection is possible. 
  9. The treatment of infected dogs is unlikely to have an impact on the population of the disease. Other canids (such as wolves, foxes, coyotes, etc) can serve as the source of infection.
  10. Treatment of all dogs with positive test results may increase doxycycline resistance. (Doxycycline is the preferred antibiotic for tick disease.)
  11. Ehrlichiosis treatment drugs have potential adverse effects. Healthy dogs could develop more problems than treatment prevents

Similar Criteria When You Treat Lyme Disease

And ehrlichiosis is not the only tick-borne disease with many criteria for diagnosis.

Veterinary Medicine states, “The criteria for diagnosing Lyme disease in dogs include:

  1. A history of exposure to Ixodes species ticks in an endemic area,
  2. Typical clinical signs,
  3. A positive serologic test result from a validated test,
  4. And, a prompt response to antibiotic therapy.

It would be unusual for a dog with clinical Lyme disease to not fulfill all these criteria.”

And, antibiotic treatment in asymptomatic dogs is not indicated

“Antibiotic therapy in asymptomatic dogs known to have been exposed to Ixodes species ticks or to be seropositive is likely not indicated in most instances … because the incidence of clinical disease in seropositive dogs is relatively low and such therapy is unlikely to eliminate the infection … The high rate of re-exposure in endemic areas also makes prophylactic therapy impractical for many animals.” – Veterinary Medicine

Should You Treat An Asymptomatic Dog?

So, what do you do if a tick bites your dog and your dog shows no symptoms? Do you get serological tests for common tick-borne diseases?

If your dog is still antibody positive after he takes antibiotics, what do you do? Treat it again?

What if your dog is still positive after a second course of treatment? Do you assume doxycycline does no harm and try again?

Doxycycline is considered a relatively safe drug but … the Plumb’s Veterinary Drug Handbook includes the adverse effects like …

  • Nausea and vomiting
  • Esophageal strictures in cats (unknown if this occurs in dogs)
  • Overgrowth (superinfections) of non-susceptible bacteria or fungi.

After review of the literature, Synbiotics shared their opinion … vets do not need to screen for ehrlichiosis and treat dogs who do not show symptoms.

So the next time you see a tick … stay calm. 

Remove the tick and watch your dog closely. If there are no symptoms, you can feel confident that your dog is healthy. No titer test needed. 

5 minutes a day. Healthier Dog.

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