What Is Ehrlichiosis?
Ehrlichiosis is a tick-borne disease caused by bacteria in the genus Ehrlichia. In dogs, the most important species worldwide and across much of the United States is Ehrlichia canis, transmitted primarily by the brown dog tick (Rhipicephalus sanguineus). Other species such as Ehrlichia ewingii and Ehrlichia chaffeensis also infect dogs (and sometimes people) via lone star ticks and related vectors, depending on the region.
After an infected tick feeds, the bacteria invade white blood cells. Disease can be mild and brief, or it can progress through acute, subclinical, and chronic phases — which is why some dogs seem to “get better,” then become seriously ill weeks to months later.
Why it matters
Chronic ehrlichiosis can devastate bone marrow and immune function. Dogs may develop severe anemia, bleeding tendencies, and secondary infections. Early antibiotics and year-round tick prevention dramatically change outcomes.
Phases and Signs
Acute phase (often 1–3 weeks after infection): fever, lethargy, reduced appetite, weight loss, swollen lymph nodes, discharge from eyes or nose, and sometimes neurologic signs. Bloodwork may show low platelets (thrombocytopenia), which can lead to bruising or nosebleeds.
Subclinical phase: dogs may appear normal while the organism persists. This quiet period can last months.
Chronic phase: weakness, pale gums, bleeding, eye inflammation, swollen limbs, joint pain, and life-threatening bone-marrow suppression. Chronic disease is harder to reverse and may require hospitalization, transfusions, or intensive supportive care.
Diagnosis and Veterinary Care
Veterinarians combine history (ticks, travel, boarding, kennels), exam findings, CBC/chemistry panels, and specific testing (in-clinic ELISA screens, PCR, and/or antibody titers). Because tick pathogens often travel together, many clinics use panels that also check for Lyme, anaplasma, and heartworm antigen.
Doxycycline is the usual first-line antibiotic when ehrlichiosis is suspected or confirmed; your vet sets dose and duration. Supportive care may include fluids, anti-nausea medication, eye care, and blood products in severe cases. Follow-up bloodwork confirms that platelets and other cell lines are recovering.
Prevention for US Households
- Apply or administer tick prevention on schedule — brown dog ticks can live indoors and in kennels, so “indoor only” dogs are not automatically safe.
- Inspect dogs after outdoor time and remove ticks the same day when possible.
- Wash bedding and vacuum regularly if you find ticks in the home; brown dog ticks can establish indoor populations.
- Screen dogs that are newly adopted from endemic regions, even if they seem healthy.
- Do not delay care for unexplained bleeding, pale gums, or prolonged fever.
When to see a vet urgently
Pale gums, collapse, labored breathing, persistent nosebleeds, bloody urine or stool, seizures, or a dog too weak to stand need emergency evaluation — do not wait for a routine appointment.
Key Takeaways
- Ehrlichiosis is a bacterial infection spread by ticks; E. canis is the classic canine form in the US.
- Disease may quiet down, then return as a dangerous chronic illness.
- Tick prevention plus early testing/treatment protect dogs far better than watching and waiting.
FAQ
Can people catch ehrlichiosis from their dog?
People get certain Ehrlichia species from tick bites, not typically from casual contact with an infected dog. Shared yards and trails are the link.
How is ehrlichiosis different from anaplasmosis?
Both are tick-borne bacterial diseases that can cause fever and low platelets, but they involve different organisms and often different tick species. Combo tests help sort them out.
Will my dog be immune after infection?
Not reliably. Reinfection is possible, so keep prevention going for life.