Anaplasmosis is a bacterial tickborne disease. Some dogs with anaplasmosis may never show signs of illness or require treatment, but those that do commonly get a fever and respond quickly to antibiotics. The use of year-round tick preventatives is the best strategy to avoid infection.  


Anaplasmosis is caused by the bacteria Anaplasma phagocytophilum, and it is spread by black-legged ticks. Once bitten, a tick must stay attached for 24-48 hours to transmit the bacteria. After that, it takes 1-2 weeks for clinical signs of anaplasmosis to occur.  

In the United States, anaplasmosis is most common in the Northeast, upper Midwest and West Coast.  

Clinical signs 

Dogs exposed to anaplasmosis may never develop any clinical signs, or the signs may be vague and non-specific.  

The most common clinical signs of anaplasmosis include: 

  • Fever 

  • Decreased appetite 

  • Lethargy  

  • Dehydration 

Other signs could include lameness, vomiting and diarrhea, or in rare circumstances, bleeding from the nose, neck pain and seizures.  


Anaplasmosis is often diagnosed with a blood test to detect antibodies. A positive antibody test does not necessarily indicate active infection needing treatment, but rather previous exposure, which can remain detectable for several months.  

Your veterinarian may recommend follow-up testing to confirm a diagnosis and blood work to help determine if your dog has an active infection that requires treatment.  


Anaplasmosis is commonly treated with the antibiotic doxycycline. After starting medication, dogs often start to feel better in 1-2 days, but require treatment for at least two weeks. An extended course of four weeks may be necessary for patients infected with Lyme disease at the same time. A patient with a positive antibody test, but no clinical signs or changes in blood work, does not require antibiotic treatment. 

Your veterinarian will assess the need for additional treatments, such as pain medications or fluid therapy. In some cases, an immune-mediated component may occur, making treatment with steroids and other supportive care necessary, depending on the patient’s clinical signs.  


Many dogs that test positive for anaplasmosis never become ill or require treatment. Dogs that become ill from anaplasmosis and receive treatment have a good prognosis.  

Re-infection can occur if they are re-exposed to ticks carrying the disease. Any dog testing positive for anaplasmosis should have their tick control and prevention measures re-evaluated.  


Anaplasmosis can infect multiple mammal species but is not directly transmittable between animals, including, but not limited to dogs, cats, horses, cows, sheep, goats and humans.  

Similarly, humans get infected with Lyme disease from being directly bitten by ticks and not from interacting with dogs that have Lyme disease. However, dogs can increase your exposure to these ticks when they brush against vegetation where the ticks live and then unintentionally transport the ticks into your living environment.  

Limit the opportunities for your pet to bring ticks into your space by implementing tick control measures. Additionally, it is important to check both of your bodies for ticks after being in areas with a high prevalence, such as in tall grass, forest litter and brushing against other vegetation.   


There is no vaccination to prevent anaplasmosis. The best ways to avoid anaplasmosis and other tick-borne diseases in dogs include:  

  • Year-round tick preventatives for all pets  

  • Backyard management (e.g. keep lawns cut short, remove leaf piles, etc.)  

  • Routine tick checks  

  • Prompt removal of ticks   

  • Avoid high-risk areas (wooded areas with a dense understory, tall grass and leaf litter)