Tick-Borne Diseases in Dogs: Lyme, Ehrlichia, and Anaplasmosis Explained

Ticks Carry More Than Lyme Disease

When most people think of tick-borne disease in dogs, Lyme disease is the first name that comes to mind. But the tick that transmits Lyme — the Ixodes deer tick — also transmits anaplasmosis, and other tick species transmit ehrlichiosis, Rocky Mountain spotted fever, and babesiosis. Each disease has different clinical presentations, geographic distribution, and treatment requirements. Knowing them by name helps you recognize the signs and have more informed conversations with your veterinarian.

Lyme Disease (Borrelia burgdorferi)

Transmitted by the Ixodes scapularis (blacklegged/deer tick) in the Northeast and Upper Midwest, and Ixodes pacificus on the West Coast. An attached tick must feed for approximately 36-48 hours to transmit the bacteria, which is why daily tick checks and prompt removal are effective prevention.

Clinical signs: Many infected dogs never show symptoms. When disease occurs, the most common presentation is sudden-onset lameness (often shifting between legs), fever, lethargy, and reduced appetite. The classic "bull's-eye rash" seen in human Lyme disease is not reliably seen in dogs. A more serious complication is Lyme nephritis — immune-mediated kidney disease that can develop in some dogs (particularly Labrador and Golden Retrievers appear to be at elevated risk) and is potentially fatal.

Diagnosis: Blood test (4Dx or similar combination test that includes Lyme antibody).

Treatment: Doxycycline, typically for 4 weeks. Most dogs with acute Lyme disease respond well. Lyme nephritis has a more guarded prognosis.

Vaccination: A Lyme vaccine is available for dogs and is recommended in endemic areas in addition to, not instead of, tick prevention.

Ehrlichiosis (Ehrlichia canis and others)

Transmitted primarily by the brown dog tick (Rhipicephalus sanguineus) and lone star tick (Amblyomma americanum). More common in the South and Southeast US, though spreading.

Clinical signs: Fever, lethargy, reduced appetite, weight loss, swollen lymph nodes, and notably: low platelet counts leading to bruising, nose bleeds, or unusual bleeding. Chronic ehrlichiosis can cause bone marrow suppression with serious long-term consequences.

Diagnosis: 4Dx test detects antibodies to Ehrlichia. PCR testing can detect active infection.

Treatment: Doxycycline for 4 weeks minimum. Early treatment leads to much better outcomes than delayed treatment.

Anaplasmosis (Anaplasma phagocytophilum)

Transmitted by the same Ixodes tick that carries Lyme disease, with similar geographic distribution.

Clinical signs: Similar to Lyme and Ehrlichia — fever, lethargy, reduced appetite, joint pain, and low platelets. Can be difficult to distinguish clinically from the others.

Diagnosis: 4Dx test; PCR for confirmation.

Treatment: Doxycycline, typically 2-4 weeks.

Rocky Mountain Spotted Fever (RMSF)

Transmitted by the American dog tick and Rocky Mountain wood tick. Despite the name, occurs throughout the US. Among the most rapidly serious tick diseases — severe cases can progress from initial symptoms to life-threatening illness within a week. Signs include fever, vomiting, abdominal pain, joint pain, and in severe cases neurological signs and bleeding.

Treatment: Doxycycline — early treatment is critical.

The Shared Lesson

Year-round tick prevention using proven prescription products, annual 4Dx testing, and prompt evaluation of any febrile illness, lameness, or unusual bleeding in dogs with outdoor exposure are the cornerstones of tick-borne disease management.