What is ehrlichiosis?
Updated By PetymFacts checked against official sources on
Quick answer
Ehrlichiosis is a disease of dogs caused by Ehrlichia canis, a bacterium carried by the brown dog tick. Signs appear 1 to 3 weeks after infection: fever, dullness, bleeding such as nosebleeds or bruising, and enlarged lymph nodes. Some dogs seem to recover but carry the infection silently and later develop a severe chronic form.
Also called canine ehrlichiosis, canine monocytic ehrlichiosis, Ehrlichia canis, tropical canine pancytopenia.
Key facts
- Ehrlichia canis is carried by the brown dog tick; signs appear 1 to 3 weeks after infection. Merck Veterinary Manual
- Signs include fever, bleeding such as nosebleeds, bruising and black stools, and an enlarged spleen and lymph nodes. Merck Veterinary Manual
- Some dogs go on to a chronic form after the first illness. Merck Veterinary Manual
- Ehrlichia canis has been confirmed by molecular testing in dogs in eastern India. Pathogens (2024), OUAT Bhubaneswarstudy
- Co-infection with other tick-borne pathogens is common in Indian dogs, as in a study from Andhra Pradesh. Veterinary Research Forum (2023)study
What are the three stages of ehrlichiosis?
Not every dog passes through all three. Merck notes most dogs clear the infection within 2 to 4 weeks, and the chronic form is rare.
- Acute stage
- Starts 1 to 3 weeks after the infected tick bite: fever, dullness, poor appetite, swollen lymph nodes, and sometimes bleeding. Merck Veterinary Manual
- Subclinical stage
- The dog looks well but stays infected, sometimes for months or years, with low platelet counts that only a blood test shows. Parasites & Vectors (2015)study
- Chronic stage
- In a minority of dogs the bone marrow is damaged: severe anaemia, bleeding, weight loss, eye inflammation and repeated infections. This form is serious and slower to respond. Indian Journal of Veterinary and Animal Sciences Research (2026), TANUVASstudy
What does ehrlichiosis look like at home?
The early signs are easy to put down to the heat or a bad day: a dog that is quiet, off its food and warm to the touch. Watch for bleeding, which points strongly to a tick-borne infection: nosebleeds, small red spots on the gums or belly skin, bruises, or black, tarry stools from bleeding in the gut. Some dogs have eye problems or become lame.
Because the signs overlap with babesiosis and other tick infections, which often occur together in Indian dogs, the vet will run blood tests: a blood count to look at platelets, and antibody or PCR tests to identify the organism.
How is ehrlichiosis treated?
With a course of an antibiotic chosen by your vet, usually for about four weeks, plus supportive care; dogs with severe bleeding or anaemia may need a transfusion. In the acute stage the fever usually settles within a day or two of starting treatment, but the whole course must be finished. Blood changes in chronic cases can take 3 to 6 months to settle, and your vet will recheck. Never stop or change the medicine without your vet.
How do you prevent ehrlichiosis?
Prevention rests on tick control all year round, on indoor dogs too, with a product licensed for dogs, plus daily checks and quick removal of any tick. The brown dog tick breeds indoors, so a heavily infested home or kennel may need treating. Before a stay away make sure tick prevention is current, and afterwards keep watching for 1 to 3 weeks or more.
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Questions owners ask
What are the symptoms of ehrlichiosis in dogs?
- Fever, dullness, poor appetite and swollen lymph nodes, starting 1 to 3 weeks after infection, often with bleeding such as nosebleeds, bruising or black stools. Some dogs recover from this stage but stay infected and later develop a chronic form with severe anaemia and bleeding. See your vet for a blood test.
Is ehrlichiosis contagious between dogs?
- Not by ordinary contact. It spreads through the bite of an infected brown dog tick, and can also pass through a blood transfusion from an infected dog. A household with one infected dog likely has ticks, so all dogs in the home need tick control and a vet's advice.
Can a dog fully recover from ehrlichiosis?
- Many dogs treated in the acute stage recover well; the fever usually settles within a day or two of starting treatment, and the whole course must be finished. The rarer chronic form, where the bone marrow is affected, is slower to respond, with blood changes lasting months. Early diagnosis gives the best chance.
Is ehrlichiosis the same as tick fever?
- It is one of the infections Indian owners and vets call tick fever. The other common one is babesiosis, and a dog can have both at once. A blood test tells them apart, which matters because they need different medicines.
Keep reading
Related terms
More in vaccines and parasites
- BabesiosisBabesiosis is a disease of dogs caused by Babesia, tiny parasites that live in and destroy red blood cells. It is spread mainly by ticks, and in India one species, Babesia gibsoni, also spreads through dog fights and blood transfusions. Signs are anaemia with pale gums, weakness, jaundice and red or brown urine. Dogs that recover can relapse.
- Booster vaccineA booster is a repeat dose of a vaccine that tops up or confirms a pet's protection. Puppies and kittens get a booster at about 26 weeks after their first course. After that, modern core vaccines for distemper, parvovirus and panleukopenia protect for years, while leptospirosis, kennel cough and most killed vaccines need a booster every year.
- Brown dog tickThe brown dog tick, Rhipicephalus sanguineus, is the most common tick on dogs in the tropics, including India. Unlike most ticks it lives and breeds indoors, in homes and kennels, as well as outdoors. It spreads ehrlichiosis and one form of babesiosis, the infections Indian owners call tick fever, so tick control is needed all year.
- Core vaccinesCore vaccines are the vaccines every dog or cat should have, wherever it lives, because they protect against widespread, serious diseases. For dogs they cover distemper, adenovirus and parvovirus; for cats, panleukopenia, herpesvirus and calicivirus. In India rabies is core for both, and WSAVA also treats leptospirosis vaccine as core for dogs where the disease is endemic.
- DewormingDeworming is giving a pet medicine, chosen by your vet, to kill intestinal worms such as roundworms, hookworms and tapeworms. Puppies can be born with roundworms and catch more from their mother's milk, so deworming starts in the first weeks of life. Some dog and cat worms can infect people, especially children, so regular deworming protects the family too.
- DHPPi vaccineDHPPi is the combined core vaccine for dogs printed on many Indian vaccine cards. The letters stand for distemper (D), hepatitis from canine adenovirus (H), parvovirus (P) and parainfluenza (Pi). DHPPiL adds leptospirosis (L). It is the same vaccine group that US cards call DHPP or DA2PP, and puppies start it at 6 to 8 weeks.
- Flea and tick preventionFlea and tick prevention means regularly protecting a pet from these parasites with a product your vet recommends, plus checking the coat and treating the home. Tropical guidelines say dogs and cats in places like India should be protected all year, including indoor pets. Use products licensed for the species, and never put a dog product on a cat.
- FleasFleas are small, wingless, blood-feeding insects. The cat flea, Ctenocephalides felis, is the most common flea on dogs and cats worldwide, and the main flea on dogs studied in India. Fleas cause itching, flea allergy, tapeworm and, in heavy infestations, anaemia in puppies and kittens. Most of the flea life cycle happens in the home.
- FVRCP vaccineFVRCP is the core combined vaccine for cats. It protects against feline viral rhinotracheitis (herpesvirus), calicivirus and panleukopenia. Indian cards often show a brand name from the vial sticker instead, such as Tricat. Kittens start at 6 to 8 weeks, with doses every 2 to 4 weeks until 16 weeks or older, then a booster at about 26 weeks.
- HeartwormHeartworm, Dirofilaria immitis, is a long worm that lives in the heart and lung blood vessels of dogs and, less often, cats. It is spread by mosquito bites and is widespread in tropical regions, including parts of India. Signs include coughing, tiring on exercise and weight loss. It can be prevented, and dogs should be tested yearly.
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Sources
Each source was opened and read on the date shown. How Petym checks its sources
- Merck Veterinary Manual: Ehrlichiosis in dogs (opens in a new tab)
- Companion Animal Parasite Council: Ehrlichia and Anaplasma (dog) (opens in a new tab)
- Queensland Government (Business Queensland): Canine ehrlichiosis (opens in a new tab)
- Tropical Council for Companion Animal Parasites: Guidelines for the control of ectoparasites of dogs and cats in the tropics (2022) (opens in a new tab)
- European Scientific Counsel Companion Animal Parasites (ESCCAP): GL5: control of vector-borne diseases in dogs and cats (5th edition, 2024) (opens in a new tab)
- Pathogens (2024), OUAT Bhubaneswar: Ehrlichia canis in Eastern India: molecular confirmation, epidemiology and pathophysiology (opens in a new tab)
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- Veterinary Research Forum (2023): Co-infections of major tick-borne pathogens of dogs in Andhra Pradesh, South India (opens in a new tab)
- Parasites & Vectors (2015): Guideline for veterinary practitioners on canine ehrlichiosis and anaplasmosis in Europe (opens in a new tab)
- Indian Journal of Veterinary and Animal Sciences Research (2026), TANUVAS: Canine monocytic ehrlichiosis: pathogenesis, diagnosis, treatment and outcomes (review) (opens in a new tab)
- Parasites & Vectors (2010): Canine vector-borne diseases in India: a review of the literature (opens in a new tab)