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Ehrlichiosis in Dogs

What Is Ehrlichiosis in Dogs?

Ehrlichiosis in dogs is a disease transmitted through tick bites, caused by infectious bacteria from the Ehrlichia genus. Ehrlichia comprises numerous species, but the primary culprits for ehrlichiosis in dogs in the United States are E. canis and E. ewingii. While all strains are tick-borne, the specific tick species responsible may vary depending on the Ehrlichia strain. Moreover, these bacteria infect and reside in different types of white blood cells.

E. canis, also known as tracker dog disease or tropical canine pancytopenia, was first identified during the Vietnam War. Breeds like German Shepherds, Doberman Pinschers, Belgian Malinois, and Siberian Huskies tend to develop a more severe form of the disease compared to others. E. canis infects monocytes, a type of white blood cell, upon entering the host.

On the other hand, E. ewingii is the predominant form of ehrlichiosis in North America, residing within granulocytes, another type of white blood cell, once it enters the host. E. ewingii infections, scientifically known as canine granulocytic ehrlichiosis, generally attract less attention as they are typically less severe than E. canis infections. Most dogs infected with E. ewingii exhibit mild symptoms or may even remain asymptomatic.

Symptoms

The symptoms of Ehrlichiosis in dogs caused by E. canis can be categorized into three phases: acute, subclinical, and chronic.

The acute phase, occurring one to three weeks after a tick bite, marks the initial stage of Ehrlichiosis caused by E. canis. During this period, the bacteria replicate and adhere to white blood cells. Typical clinical signs observed during the acute phase encompass:

  • Fever
  • Lethargy/depression
  • Anorexia/weight loss
  • Enlarged lymph nodes
  • Lameness
  • Vomiting/diarrhea
  • Cough
  • Abnormal bruising and bleeding
  • Neurologic symptoms like loss of balance or stumbling

Treatment during the acute phase usually results in complete clearance of the infection, with dogs returning to their normal state. However, without treatment, dogs often progress to the subclinical phase within one to four weeks.

The subclinical phase, dogs remain infected but display no outward signs of illness. The bacteria remain concealed in the spleen for months or even years. While clinical signs are absent, some alterations in blood work may be evident, such as a slightly reduced platelet count and potentially elevated blood protein (globulin). Not all dogs advance from the subclinical phase to the chronic phase, as some may naturally clear the infection.

In the chronic phase, where the disease persists long-term, dogs fail to eliminate the bacteria and relapse into illness. Clinical signs during this phase include:

  • Abnormal bleeding: Approximately 60 percent of dogs in the chronic phase exhibit decreased platelet counts, leading to anemia.
  • Eye inflammation (uveitis), eye bleeding (hyphema), or blindness
  • Neurological symptoms like loss of balance or stumbling
  • Increased urination (polyuria) and increased drinking (polydipsia) due to kidney damage
  • Lameness/swollen limbs

Prognosis for dogs in the chronic phase is poorer, and the condition can become fatal. Clinical signs of E. ewingii infection are generally milder compared to E. canis and may include fever and swollen joints. Some dogs infected with E. ewingii may not exhibit any clinical signs at all.

Causes

Ehrlichiosis in dogs is caused by different species of Ehrlichia, with E. canis being transmitted by the brown dog tick (Rhipicephalus sanguineus) and E. ewingii being transmitted by the Lone Star tick (Amblyomma americanum). Transmission of the disease can occur within a short span of three to six hours after the tick attaches, underscoring the importance of prompt tick removal.

While humans cannot contract E. canis, they remain susceptible to other forms of ehrlichiosis, including E. ewingii. However, ehrlichiosis is not considered zoonotic, meaning humans cannot contract the disease directly from infected dogs. Nevertheless, humans can contract the disease through tick bites. If there is suspicion of exposure to ehrlichiosis, immediate medical attention is advised.

Diagnosis

When diagnosing Ehrlichiosis in dogs, veterinarians typically begin by gathering a comprehensive history of travel and recent tick exposure. A thorough physical examination follows to assess for symptoms like fever, joint swelling/pain, and enlarged lymph nodes. To establish a baseline evaluation, a complete blood count, serum blood chemistry, and urinalysis are usually conducted.

Veterinarians inquire about recent travel history where tick exposure may have occurred and conduct a comprehensive examination of the dog. They may order various blood tests, including urinalysis and serum blood chemistry, to establish a diagnosis. If Ehrlichiosis is suspected, additional specialized laboratory testing may be recommended.

Most veterinarians employ a Snap 4Dx test to annually screen dogs for heartworms. Alongside heartworms, the test also screens for Lyme disease, Anaplasma, and Ehrlichia. According to the manufacturer’s website, the test detects antibodies for E. canis or E. ewingii. In the absence of clinical signs and in a healthy pet, a positive Snap test for Ehrlichiosis can be perplexing and may necessitate further testing.

Sometimes, the test results in a false positive (indicating a negative result). However, it’s likely that the pet was exposed to the bacteria through an infected tick bite. Based on the presence or absence of symptoms, veterinarians may choose one of three options:

  • Monitor the dog without additional therapy
  • Initiate treatment for Ehrlichiosis
  • Recommend further testing, such as PCR amplification.

Treatment

Ehrlichiosis in dogs is commonly treated with a 28- to 30-day course of antibiotics, with Doxycycline being the most frequently prescribed medication. Dogs in the acute or subclinical phases generally do not require hospitalization and can be managed as outpatients at home with minimal supportive care, which may include pain medications and appetite stimulants. However, dogs with chronic ehrlichiosis may necessitate hospitalization for intensive supportive care, which may involve blood transfusions, steroids, intravenous fluids, and nutritional support.

It’s common for dogs with ehrlichiosis to be concurrently infected with other tick-borne diseases, which can complicate both diagnosis and treatment. Therefore, veterinarians will tailor a treatment plan to address the specific needs of each individual dog.

Living and Management

Dogs diagnosed with acute or subclinical ehrlichiosis caused by E. canis typically show improvement within one to two days of starting treatment and have a favorable prognosis for recovery. Those with E. ewingii infection also tend to recover swiftly once antibiotics are initiated. Although dogs may retain antibodies in their bloodstream for several years post-recovery, they are essentially cured of the infection.

Regrettably, the prognosis for dogs suffering from chronic E. canis infection remains guarded, as this stage can prove fatal. Surviving dogs can potentially become re-infected with ehrlichiosis later in life, as immunity against the disease is not lifelong.

Ehrlichiosis cannot be transmitted directly from one dog to another, but if multiple pets were exposed to the same tick-infested area, consulting a veterinarian regarding testing and/or treating all household dogs is recommended.

While ehrlichiosis is not zoonotic, meaning it cannot be transmitted from dogs to humans, humans can contract the infection directly from a tick bite. If there’s suspicion of exposure to ehrlichiosis through a tick bite, seeking immediate medical attention is advised.

Prevention

Thankfully, most tick bites can be prevented through regular flea and tick preventative care, administered monthly. There are various options available, including topical solutions, tablets, and chewable medications. Your veterinarian can assist you in determining the most suitable option for your pet.

For those residing near wooded areas where ticks are prevalent, it’s advisable to keep your dog away from these environments, particularly since there is currently no vaccine available for ehrlichiosis. After any outdoor excursion, it’s crucial to thoroughly inspect your dog for ticks or fleas and safely remove them. Prompt removal of ticks is the most effective defense against the transmission of any potential infection.

Ehrlichiosis in Dogs FAQs

Can ehrlichiosis in dogs be treated effectively?

Yes, with prompt and appropriate antibiotic therapy, ehrlichiosis can be effectively treated. However, antibodies may persist in the blood for years following successful treatment.

Can I contract ehrlichiosis from my dog?

No, transmission of ehrlichiosis from dogs to humans has never been documented. However, humans can acquire ehrlichiosis from ticks. Since both dogs and humans are often exposed to the same tick population, it’s possible for individuals and dogs within the same household to test positive for ehrlichiosis.

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