My Dog Has Nosebleeds and Lethargy — Ehrlichia Symptoms and When to Go to the Vet

Infection/ParasitesDiseasesMeongsiljang Veterinary Advisory Board

Canine ehrlichiosis is a bacterial blood disease transmitted by ticks, which invade white blood cells. Key signs include fever, nosebleeds, and swollen lymph nodes. If the condition progresses to the chronic stage, it can become life-threatening due to bone marrow suppression.

What Is Canine Ehrlichiosis? A Tick-Borne Bacterial Blood Infection

A close-up view of a brown ear mite attached to a dog's ear

Canine ehrlichiosis is a bacterial blood disease transmitted by ticks, with the bacteria residing inside white blood cells, particularly monocytes. Early diagnosis is key. If symptoms such as fever, loss of appetite, nosebleeds, or swollen lymph nodes appear within 1–3 weeks after a tick bite, your dog should undergo blood testing at a veterinary clinic immediately. If the condition progresses to the chronic stage, bone marrow function declines, which can become life-threatening, making treatment during the acute phase critical.

Cause and Pathogenesis — The Brown Dog Tick Is the Main Culprit

The causative agent is Ehrlichia canis, a small intracellular parasitic bacterium. The primary vector is the brown dog tick (Rhipicephalus sanguineus), which transmits the bacteria into your dog’s body through its salivary glands while feeding on blood. The longer a tick remains attached, the higher the risk of infection, so it’s important to remove any ticks you find promptly and correctly, and to use regular tick preventatives to stop attachment in the first place. Once inside the body, the bacteria multiply within mononuclear cells such as monocytes circulating in the blood, compromising the immune system and causing decreases in platelet and white blood cell counts.

Key Symptom Checklist — Signs Vary by Stage

Ehrlichia symptoms vary depending on the stage of the disease. Here are the key signs pet owners are most likely to notice first: - Fever: A low-grade to high fever (39.5°C or higher) that persists for several days - Nosebleeds and gum bleeding: Petechial hemorrhages may appear due to a drop in platelet count - Swollen lymph nodes: Lymph nodes under the jaw, in the armpits, and on the inner thighs may feel enlarged - Loss of appetite and lethargy: Your pet may refuse walks or lie down all day - Weight loss: Noticeable weight loss often occurs in the chronic stage - Eye symptoms: Uveitis or retinal hemorrhage can cause the eyes to appear cloudy

If You See These Signs, Go to the Vet Within 24 Hours

If your dog’s nosebleed won’t stop, you notice pinpoint bleeding on the gums or abdomen, or their breathing becomes rapid, seek emergency veterinary care immediately. When platelet levels drop to a critically low point, internal organ bleeding can develop rapidly. Even if you don’t recall your dog being bitten by a tick, always keep this possibility in mind for any dog that goes for walks, and please inform your veterinarian right away.

Diagnosis — Blood Tests Are Decisive

Ehrlichia cannot be definitively diagnosed through a routine physical examination alone. At the veterinary clinic, the following tests are typically performed together. A complete blood count (CBC) is used to confirm decreases in platelets and white blood cells, while a serum antibody test (using kits such as SNAP 4Dx) quickly screens for exposure to the bacteria. For a more accurate definitive diagnosis, a PCR (polymerase chain reaction) test may be conducted to directly detect the bacteria’s DNA. If chronic-stage ehrlichiosis is suspected, a bone marrow examination may be necessary.

Comparison of Acute, Subclinical, and Chronic Stages

Item	Acute phase	Subclinical phase	Chronic phase
Onset timing	1–3 weeks post-infection	6–9 weeks post-infection onward	Months to years later
Main signs	Fever, epistaxis, lymph node swelling	Outwardly normal	Severe anemia, bleeding, weight loss
Platelet count	Decreased	Slightly low or normal	Severely decreased
Treatment response	Good	Good with treatment	Poor prognosis
Treatment duration	3–4 weeks	3–4 weeks	4+ weeks, long-term management

Based on veterinary internal medicine textbook classification

Treatment — Doxycycline Is the First-Line Drug

The standard treatment for ehrlichiosis involves administering the antibiotic doxycycline for a specific period. Your veterinarian will determine the dosage and schedule based on your pet’s weight. Treatment typically needs to be continued consistently for about four weeks; stopping it prematurely, even if symptoms improve quickly, significantly increases the risk of relapse. In cases of severe anemia, a blood transfusion may be necessary, and if immune-mediated complications are present, immunosuppressants may be added to the treatment plan.

Recovery Care Points to Watch at Home

During treatment, please reduce the intensity of walks and ensure your pet gets plenty of rest. It’s very helpful to keep a daily log of whether the gums are returning to a healthy pink color, if the nosebleeds have stopped, and if the appetite is improving—this information will be invaluable at follow-up visits. Since milk and dairy products can interfere with medication absorption, please administer the medicine with a small amount of food instead. Even after treatment is complete, regular blood tests every 6 to 12 months are necessary to monitor for recurrence.

Prevention Is Far More Important Than Treatment

Ehrlichiosis is a disease that can become chronic once contracted, making prevention absolutely essential. Apply tick preventatives (such as those containing fipronil or fluralaner) consistently from spring through autumn, and after walks, check for ticks by running your fingers along the inside of the ears, between the toes, and in the armpits. Extra caution is needed in grassy areas and on hiking trails. For mixed-breed dogs, medium-to-large breeds, and other dogs with frequent outdoor activity, it is crucial not to miss a single monthly dose.

Reviewed by a veterinarian

Dr. Tony — Punnawat Phongkittirak

Veterinarian

A veterinarian who majored in veterinary medicine at Khon Kaen University, Thailand, and completed the IVSA program at North Carolina State University in the United States. Drawing on clinical experience at animal hospitals, he works in the pet healthcare field and is dedicated to building a digital care environment that connects pet parents with veterinarians.

Frequently Asked Questions

Can Ehrlichia be transmitted to humans?

There are specific types of ehrlichiosis that can infect humans, such as Ehrlichia chaffeensis, but direct transmission from dogs to people is rare. However, since ticks can bite humans too, please check your clothing and shoes after walks.

Does one treatment mean they’ll never get it again?

Not at all. Even after antibodies develop, your pet can still be infected by other strains of Ehrlichia or by the same strain again. That’s why it’s important to continue using tick preventatives even after treatment.

Can it be prevented through vaccination?

Currently, there is no commercially available Ehrlichia vaccine for dogs in Korea. The most reliable way to prevent infection is to use external parasite preventatives that effectively block tick exposure.

How much will the treatment cost?

Costs can vary significantly depending on the specific tests, medications, and veterinary clinic, so it's difficult to provide a single, fixed price. We recommend getting a comprehensive estimate that covers both the diagnostic tests and the full four-week treatment plan.

Only one pet in my multi-cat or multi-dog household has been infected. Should the other pets be tested as well?

Since they share the same environment, there’s a high chance both dogs and cats have been exposed to ticks, so we recommend testing all of them. Some pets may be in the asymptomatic, preclinical stage of infection.

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References

[1] Sykes JE. Canine and Feline Infectious Diseases, Chapter 28: Ehrlichiosis

[2] Greene CE. Infectious Diseases of the Dog and Cat, 4th Ed, Chapter 26

[3] Principles and Practices of Canine and Feline Clinical Parasitic Diseases, Chapter on Tick-borne pathogens

[4] BSAVA Manual of Canine and Feline Dermatology, 4th Ed, Tick prevention chapter