Tick-borne diseases are among the fastest-growing infectious disease threats in veterinary medicine, driven by expanding tick populations due to climate change, urbanization, and deer population growth. A single tick can transmit multiple pathogens simultaneously, and many infections remain subclinical (no visible symptoms) for months to years before causing serious illness.
- Major Tick-Borne Diseases
- Lyme Disease (Borrelia burgdorferi)
- Ehrlichiosis (Ehrlichia canis)
- Anaplasmosis (Anaplasma phagocytophilum)
- Rocky Mountain Spotted Fever (Rickettsia rickettsii)
- Testing
- Prevention
- Frequently Asked Questions
- My dog tested positive for Lyme but has no symptoms. Should I treat?
- Do tick preventatives kill ticks before they can transmit disease?
Major Tick-Borne Diseases
Lyme Disease (Borrelia burgdorferi)
- Vector: Black-legged tick (Ixodes scapularis/pacificus)
- Endemic areas: Northeast, Upper Midwest, Pacific Coast US
- Symptoms: Shifting leg lameness (limping that moves between legs), fever, lethargy, swollen lymph nodes, joint swelling. Only 5-10% of infected dogs show clinical signs.
- Serious complication: Lyme nephritis — fatal kidney disease. More common in Labradors and Golden Retrievers.
- Treatment: Doxycycline 30 days. Most dogs respond within 48-72 hours.
Ehrlichiosis (Ehrlichia canis)
- Vector: Brown dog tick (Rhipicephalus sanguineus), Lone Star tick
- Endemic areas: Southeast, South-Central US; expanding range
- Symptoms: Acute phase: fever, lethargy, weight loss, bleeding disorders (nosebleeds, bruising). Chronic phase: bone marrow suppression, pancytopenia (all blood cell lines decreased).
- Treatment: Doxycycline 28 days. Chronic cases may require longer treatment and have guarded prognosis.
Anaplasmosis (Anaplasma phagocytophilum)
- Vector: Black-legged tick (same tick as Lyme)
- Endemic areas: Same distribution as Lyme disease
- Symptoms: Fever, lethargy, joint pain, decreased platelets (thrombocytopenia). Often co-infected with Lyme.
- Treatment: Doxycycline 14-30 days. Generally good response.
Rocky Mountain Spotted Fever (Rickettsia rickettsii)
- Vector: American dog tick, Rocky Mountain wood tick, Brown dog tick
- Endemic areas: Southeast, South-Central US (despite the name, most cases are NOT in the Rocky Mountains)
- Symptoms: High fever, depression, joint/muscle pain, facial swelling, neurological signs. Can be rapidly fatal.
- Treatment: Doxycycline — early treatment is critical. Delayed treatment significantly worsens prognosis.
Testing
- 4Dx SNAP test: In-clinic rapid test detecting antibodies to Lyme, Ehrlichia, Anaplasma, and heartworm. Standard annual screening in endemic areas.
- Quantitative C6 antibody (Lyme): Measures antibody level. Used to determine if positive Lyme test represents active infection requiring treatment vs. exposure without active disease.
- CBC (Complete Blood Count): Detects thrombocytopenia (low platelets) common in tick-borne diseases.
Prevention
| Product | Type | Duration | Ticks Killed |
|---|---|---|---|
| Simparica Trio | Oral chewable | Monthly | 5 species + heartworm + fleas |
| NexGard | Oral chewable | Monthly | Black-legged, American dog, Brown dog, Lone Star |
| Bravecto | Oral chewable | 12 weeks | Black-legged, American dog, Brown dog |
| Seresto collar | Collar | 8 months | Multiple species + fleas |
Frequently Asked Questions
My dog tested positive for Lyme but has no symptoms. Should I treat?
Controversial. Many vets recommend monitoring with quantitative C6 and urine protein:creatinine ratio. Treatment is recommended if: C6 levels are high (>30 U/mL), protein is detected in urine, or clinical signs develop. A positive test alone without these findings may be monitored.
Do tick preventatives kill ticks before they can transmit disease?
Most oral preventatives kill ticks within 24-48 hours of attachment. Lyme transmission requires 36-48 hours of attachment. So effective tick prevention typically kills ticks before disease transmission — but the window is tight. No preventative is 100%, so daily tick checks in endemic areas are still recommended.
