Doxycycline for Tick-Borne Disease in Dogs and Cats: Ehrlichia, Anaplasma, RMSF, and Lyme

Bottom line.

• Doxycycline is the treatment of choice for the principal tick-borne bacterial infections in companion animals, including canine monocytic ehrlichiosis (Ehrlichia canis), canine and feline anaplasmosis (Anaplasma phagocytophilum, A. platys), Rocky Mountain spotted fever (Rickettsia rickettsii), and Lyme disease (Borrelia burgdorferi).
• Standard dose is 10 mg/kg PO or IV once daily for 28 days for Ehrlichia and Anaplasma infections; doxycycline 10 mg/kg PO q12h for 4 weeks is recommended for Lyme disease (CAPC).
• Clinical improvement in acute tick-borne disease is typically rapid (24–72 hours); a full 28-day course is still required because shorter courses have been associated with treatment failure and PCR-positive recrudescence.
• Generic doxycycline tablet formulations (e.g., DoxyVet) have documented efficacy equal to brand formulations for E. canis at 10 mg/kg/day for 28 days, providing a cost-effective option.
• Administer with food to reduce esophageal irritation; follow each dose with water or food and avoid dosing immediately before lying down.
• This is a clinician-facing evidence summary. It is not a treatment protocol; confirm drug dosing against current formularies and current CAPC/ACVIM guidelines.

Clinical facts

• Drug class: Tetracycline antibiotic; bacteriostatic; inhibits 30S ribosomal subunit, blocking protein synthesis of obligate intracellular organisms.
• Target pathogens: Ehrlichia canis (canine monocytic ehrlichiosis, CME), Ehrlichia ewingii (canine granulocytic ehrlichiosis), Anaplasma phagocytophilum (granulocytic anaplasmosis, dogs and cats), Anaplasma platys (canine cyclic thrombocytopenia), Rickettsia rickettsii (RMSF), Borrelia burgdorferi (Lyme disease, dogs), Neorickettsia spp., and Bartonella spp. (partial response).
• Standard dose (dogs and cats): 10 mg/kg PO SID (or divided q12h) × 28 days for Ehrlichia/Anaplasma; 10 mg/kg PO q12h × 4 weeks for Lyme disease. IV dosing (5 mg/kg slow IV infusion q12h) for vomiting patients.
• Esophageal safety: Doxycycline is irritating to the esophageal mucosa; esophageal stricture is a well-documented complication in cats following dry tablet administration. Always administer with food and follow with a full syringe of water (at least 6 mL) in cats; liquid suspension or doxycycline hyclate capsules dissolved in water are preferred in cats.
• Monitoring: Serum chemistry and CBC at baseline and at recheck (typically day 28 post-treatment) in dogs with thrombocytopenia or hypoalbuminemia at presentation. PCR of peripheral blood can be used to confirm clearance in persistently seropositive or clinically unresolved cases.
• Resistance: Tetracycline resistance in tick-borne Ehrlichia is not clinically established; doxycycline retains activity in all documented veterinary cases to date.

Managing a tick-borne disease case in your clinic this week?

Get an instant cited answer — no signup needed for your first question. Voyage Clinical Desk brings species-specific evidence, tick-borne disease dosing, and monitoring protocols to the case in front of you.

Try Voyage Clinical Desk

What the evidence shows

Generic doxycycline efficacy in canine monocytic ehrlichiosis

A controlled experimental study by Fourie et al. (2015, Journal of the South African Veterinary Association, PMID 26018824, PMC6138191) evaluated the efficacy of a generic doxycycline tablet (DoxyVet, 10 mg/kg PO SID × 20 days) in six Beagle dogs challenged with E. canis-infected Rhipicephalus sanguineus ticks.¹ PCR analysis at day 28 failed to detect E. canis DNA in any treated dog (100% PCR clearance at Day 28). However, four of five surviving dogs showed PCR-positive recrudescence by day 56, and a subsequent 28-day retreat (10 mg/kg SID) cleared four of those five dogs for the remaining 3-month observation period. The study confirmed generic doxycycline achieves PCR clearance in naturally infected dogs at a 10 mg/kg dosing regimen, and also directly demonstrated that a 20-day course is insufficient in some cases — supporting the current consensus recommendation of 28 days.

CAPC guidelines: Ehrlichia and Anaplasma treatment recommendations

The Companion Animal Parasite Council (CAPC) guidelines for Ehrlichia spp. and Anaplasma spp. confirm that doxycycline 10 mg/kg PO q24h (or divided q12h) for 28 days is the recommended treatment for all Ehrlichia and Anaplasma infections in companion animals.² CAPC notes that clinical improvement is typically seen within 24–72 hours of initiating treatment; failure to improve within 24–48 hours should prompt re-evaluation of the diagnosis. Reinfection after treatment is possible because protective immunity does not develop reliably, and PCR-positive recrudescence has been documented — further underscoring the importance of completing full-length courses and re-testing seropositive dogs in endemic areas.

Practical species-specific considerations

Dogs: The acute presentation of E. canis CME (fever, lethargy, lymphadenopathy, thrombocytopenia, epistaxis) responds rapidly to doxycycline; complete blood count recovery typically lags clinical improvement. Chronic CME with pancytopenia and bone marrow hypoplasia carries a guarded prognosis even with appropriate therapy. RMSF is a veterinary and public health emergency: aggressive early treatment with doxycycline is critical, as delays beyond the first 24–48 hours significantly worsen outcome.

Cats: Doxycycline is used for A. phagocytophilum in cats, though feline anaplasmosis is less commonly diagnosed and typically mild. Esophageal stricture risk in cats is a genuine clinical concern with tablet administration; using a compounded liquid or gel-cap formulation with food, followed by a water flush, is strongly preferred. Dose: 10 mg/kg SID for 28 days (same as dogs); some sources use 5 mg/kg BID for cats to reduce peak esophageal drug concentrations.

How this fits clinical practice

Doxycycline at 10 mg/kg/day for 28 days remains the cornerstone of tick-borne disease treatment in companion animal practice, supported by decades of evidence and CAPC guidelines. The practical points that most commonly cause treatment failure or complication are: (1) using too short a course (< 28 days), which predisposes to PCR-positive recrudescence as shown by Fourie 2015; (2) administering doxycycline tablets to cats without esophageal protection, risking stricture; and (3) failing to counsel owners that rapid clinical improvement at 48–72 hours does not mean the full course can be discontinued. For practices in endemic areas, anaplasma seropositivity on point-of-care screening tests should be interpreted in clinical context — subclinical PCR-positive dogs may not require treatment per se, but symptomatic dogs with any positive tick-borne screen should receive a full 28-day course promptly given the rapid clinical benefit.

Always confirm drug dosing, species-specific formulation guidance, and tick-borne disease testing protocols against current CAPC guidelines and formulary.

Voyage Clinical Desk

From clinical question to SOAP draft — cited differentials, live dose calculators, owner handouts. Trained on the veterinary canon (Plumb's, Ettinger, JVIM, ACVIM consensus, 50,000+ indexed references). First answer free, no signup.

Open Voyage Clinical Desk

References

1. Fourie JJ, Stanneck D, Luus HG, et al. 2015. The efficacy of a generic doxycycline tablet in the treatment of canine monocytic ehrlichiosis. J S Afr Vet Assoc 86(1):1252. https://pubmed.ncbi.nlm.nih.gov/26018824/
2. Companion Animal Parasite Council (CAPC). Ehrlichia spp. and Anaplasma spp. Treatment Guidelines. https://capcvet.org/guidelines/ehrlichia-spp-and-anaplasma-spp/

Changelog

• 2026-07-02: First published.