Tick fever in dogs: signs, diagnosis and prevention

This article covers two tick-borne infections of dogs, ehrlichiosis and babesiosis. Ehrlichiosis is caused by bacteria that infect white blood cells, and babesiosis by parasites that infect red blood cells. Between them the signs can include fever, weakness, pale gums, red or brown urine and bleeding, and a vet needs blood tests to confirm which infection is present. A dog with these signs needs a vet. Merck says tick control is the most important step in preventing ehrlichiosis, and the tropical guideline advises protecting dogs against ticks throughout the year.

Go to a vet now if your dog has been exposed to ticks and has a fever, seems very weak or collapses; has pale gums; has red, brown or yellow-orange urine or jaundice (a yellow tinge to the gums, skin or eyes); or has nosebleeds, blood in the urine or faeces, or unusual bruising. The tropical guideline describes babesiosis that causes sudden collapse, and Merck says it can range from mild to rapidly fatal. The guideline also calls one Babesia species an important cause of death in puppies under 12 weeks. Remove any tick you find, but do not wait for signs to settle.

What causes ehrlichiosis and babesiosis, and how do dogs catch them?

Ehrlichiosis is usually caused by Ehrlichia canis. The Merck Veterinary Manual says these bacteria can live only inside other cells and are spread by ticks that become infected by biting infected animals. Babesiosis is a tick-borne disease caused by Babesia parasites that infect red blood cells (Merck). The Tropical Council for Companion Animal Parasites (TroCCAP) calls it one of the most common and significant diseases of dogs in the tropics, mainly through two species, Babesia vogeli and Babesia gibsoni.

The brown dog tick is central: TroCCAP says it is the most common tick on dogs in the tropics and can complete more than one generation a year there. Merck’s professional manual says E. canis appears to be spread mainly by this tick, and TroCCAP links B. vogeli to it. The Companion Animal Parasite Council (CAPC), in its 2023 tick guideline, says brown dog ticks live inside and around homes and kennels. A 2023 review lists Rhipicephalus sanguineus and R. haemaphysaloides among the ticks reported to carry ehrlichiosis in India.

Signs can take weeks to appear. Merck’s professional manual says the acute form of ehrlichiosis occurs within 1 to 3 weeks after infection, and TroCCAP gives an incubation period of 1 to 6 weeks for babesiosis.

What are the signs of ehrlichiosis and babesiosis in dogs?

The sources describe these patterns:

Infection	Signs reported
Ehrlichiosis, early	Fever, swollen lymph nodes, enlarged spleen, low platelets on a blood test, poor appetite, low energy, stiffness or reluctance to walk, swollen legs, cough or trouble breathing (Merck)
Ehrlichiosis, long-term	Severe weight loss, kidney failure, inflammation of the lungs, eyes, brain or spinal cord, poor coordination or weakness, and bleeding such as nosebleeds, blood in urine or faeces, or bruising (Merck)
Babesiosis, sudden (per-acute)	Rapid collapse from shock, pale gums, fast heart rate, weak pulse, profound weakness; body temperature is more often low than high (TroCCAP)
Babesiosis, acute	Poor appetite, depression, vomiting, pale gums, dehydration, jaundice, and red, brown or yellow-orange urine (TroCCAP)
Babesiosis, long-term	Vague signs such as poor appetite, weight loss, swollen glands, nasal discharge and bleeding; TroCCAP says concurrent ehrlichiosis may be involved

Some dogs show nothing obvious. VCA Animal Hospitals describes a subclinical phase of ehrlichiosis in which the organism is present but not causing outward signs, and says a dog in this phase may show only lab changes such as low platelets. Merck adds that German Shepherd Dogs are more likely to develop the long-term form of ehrlichiosis.

Why does a vet have to test for ehrlichiosis and babesiosis?

Because the signs overlap with other illnesses. Merck says babesiosis can be confused with other conditions that cause fever, anaemia, destruction of red blood cells, jaundice or red urine, and that laboratory tests should confirm it. Its professional manual lists leptospirosis among the diseases that can look like acute ehrlichiosis; see the leptospirosis vaccine and Kerala dogs article for that infection.

Because more than one infection may be involved. TroCCAP tells vets investigating babesiosis to search for other infectious agents, especially Ehrlichia, and says long-term cases may have concurrent ehrlichiosis or another significant disease.

And because treatment of babesiosis is not simple. TroCCAP says many drugs have been used for babesiosis but few are consistently reliable, and only a few work against both the large and small forms of the parasite.

How do vets diagnose and treat these infections?

Merck says ehrlichiosis is diagnosed with blood tests, and its professional manual explains that blood abnormalities are common with many vector-borne infections, so additional testing is required. Antibody tests can be negative early: the manual says seroconversion can take up to 4 weeks in some animals, so when acute ehrlichiosis is strongly suspected a repeat test is advised 2 to 4 weeks after the first. VCA notes that antibody screening looks for evidence of exposure to the organism.

PCR, a test for the germ’s DNA, can detect infection earlier but can miss it when few organisms are present or after antibiotics have started (Merck). For babesiosis, TroCCAP says vets look for the parasite in a stained blood smear, may use PCR, and should assess how severe the anaemia is. It warns that antibody tests can be falsely negative in acute infection.

Treatment depends on the infection, and this article names no medicines on purpose. For ehrlichiosis, Merck says treatment is usually a course of antibiotics and fever often improves soon after it starts; VCA says the course is generally about four weeks. Merck adds that blood changes can take months to resolve in long-term cases and severe bleeding can need transfusions. VCA says a healthy dog that merely tests antibody-positive may not need treatment, and that treating can promote antimicrobial resistance. It advises talking to your vet about the treatment plan.

For babesiosis, Merck says the vet prescribes the medication, supportive care helps, and transfusions can be life-saving in very anaemic dogs. TroCCAP says few treatments, if any, clear the infection completely, most dogs stay lifelong carriers, and relapse can follow stress, immune-suppressing treatment or other illness. VCA says dogs that recover from babesiosis should never be blood donors.

How do you prevent ehrlichiosis and babesiosis in dogs?

Merck says tick control is the most important step. TroCCAP says dogs in the tropics should be protected throughout the year, and that even mostly indoor dogs may be exposed, for instance at parks or when groomed. It advises regular use of products with repellent and fast-killing effects, as labelled, with protection lasting from some weeks to several months.

• Choose products with your vet. TroCCAP advises products licensed for dogs and cats, and warns that highly concentrated synthetic pyrethroids (except flumethrin) and amidines are toxic for cats.
• Check your dog. TroCCAP lists the ears, armpits, groin, around the eyes and between the toes as common attachment sites. Merck’s professional manual says it is unrealistic to expect owners to find all ticks in a dog’s coat.
• Remove ticks promptly. TroCCAP says all visible ticks should be removed promptly to reduce the risk of transmission. Merck advises fine tweezers, grasping close to the skin and pulling straight out; CAPC’s 2023 tick guideline says gloves should be worn in case a tick is crushed during removal.
• Heavy infestations. TroCCAP says hand removal may not be feasible with very many ticks, and a fast-acting product may be needed. Ask your vet.
• Deal with the home. CAPC’s 2023 tick guideline says an established brown dog tick infestation in a home may take several months to bring under control and that a licensed exterminator’s services are necessary.
• Avoid tick-heavy areas when possible (Merck).

Frequently asked questions

Can ehrlichiosis or babesiosis pass between dogs?

Ticks are the main route. For babesiosis, TroCCAP lists ticks, mother to puppies, blood transfusion and, for B. gibsoni, fighting. Merck’s professional manual says ehrlichiosis can also be transmitted by blood transfusion.

Is there a vaccine for ehrlichiosis or babesiosis?

For ehrlichiosis, CAPC’s guideline (last updated 2015) says vaccines are not available. For babesiosis the sources differ: Merck says a vaccine based on some Babesia types exists but does not protect against all types, while VCA says no effective vaccine is available. The routine puppy vaccines in the dog vaccination schedule in India are for other diseases.

Can indoor dogs get these infections?

TroCCAP says even dogs living mostly indoors may be exposed to ticks, and CAPC’s 2023 tick guideline says brown dog ticks live inside and around homes.

Can people catch ehrlichiosis or babesiosis from dogs?

VCA says you cannot get ehrlichiosis from your dog, only from a tick bite, and Merck says an infected dog signals that ticks, and tick-borne disease risk, are present in the area. For babesiosis, TroCCAP lists the dog species as not zoonotic, while Merck says it is unclear whether they are the same as those that infect people. A 2023 review notes that E. canis was long thought not to infect people, but recent studies suggest it might.

Can a dog carry these infections without signs?

VCA describes a subclinical phase of ehrlichiosis with no outward signs of disease. TroCCAP says dogs that survive babesiosis become lifelong carriers even after appropriate treatment.

Sources

This article is general information, not a diagnosis; see the disclaimer and editorial policy.

• Tropical Council for Companion Animal Parasites (2022). Guidelines for the control of ectoparasites of dogs and cats in the tropics, 1st edition. https://www.troccap.com/2017press/wp-content/uploads/2022/01/TroCCAP-Canine-Feline-Ecto-Guidelines-English-v1.pdf
• Tropical Council for Companion Animal Parasites. Guidelines for the diagnosis, treatment and control of canine endoparasites in the tropics: Babesia (web page). https://www.troccap.com/canine-guidelines/other-systems/babesia/
• Merck Veterinary Manual, pet owner version (2026). Ehrlichiosis and related infections in dogs. https://www.merckvetmanual.com/dog-owners/disorders-affecting-multiple-body-systems-of-dogs/ehrlichiosis-and-related-infections-in-dogs
• Merck Veterinary Manual, pet owner version (2024). Blood parasites of dogs. https://www.merckvetmanual.com/dog-owners/blood-disorders-of-dogs/blood-parasites-of-dogs
• Palerme J-S. Merck Veterinary Manual, professional version (2026). Ehrlichiosis in dogs. https://www.merckvetmanual.com/infectious-diseases/rickettsial-diseases-in-dogs/ehrlichiosis-in-dogs
• VCA Animal Hospitals (2025, 2026). Ehrlichiosis in dogs; Babesiosis in dogs. https://vcahospitals.com/know-your-pet/ehrlichiosis-in-dogs and https://vcahospitals.com/know-your-pet/babesiosis-in-dogs
• Companion Animal Parasite Council. Ehrlichia spp. and Anaplasma spp. (2015); Ticks (2023). https://capcvet.org/guidelines/ehrlichia-spp-and-anaplasma-spp/ and https://capcvet.org/guidelines/ticks/
• Aziz MU, Hussain S, Song B, Ghauri HN, Zeb J, Sparagano OA (2023). Ehrlichiosis in dogs: a comprehensive review with emphasis on South and East Asian countries. Vet Sci 10(1):21. https://doi.org/10.3390/vetsci10010021