Anaplasmosis is a disease of dogs, and sometimes in cats, called Anaplasma phagocytophilum. This infectious organism is an unusual type of bacteria known as a rickettsial agent/bacterium.

The disease is transmitted to our pets through a tick bite. As with some other tick-borne diseases, a tick must remain attached to the pet for more than 24 hours for the infection to be transferred.

This disease is found around the world in a variety of animals.

Signs of Anaplasmosis

Symptoms begin 1 to 2 weeks after the tick bite. Anaplasmosis organisms enter the bloodstream and live in the animal’s white blood cells, which aid in fighting infections. This invasion of circulating white blood cells creates inflammation throughout the body.

Signs can include poor appetite and fever. Joints are commonly affected, making the pet seem stiff or painful or appear to have trouble walking. Sometimes pets may have signs associated with bleeding as well. A bloody nose, dark bloody stool, or bruising may be seen.

Not all pets will have symptoms. Some pets will only appear sick for a short time, then start to improve. We don’t fully understand why this happens, but it may be associated with a pet’s ability to fight off the infection. 

Diagnosing Anaplasmosis

Anaplasmosis in dogs and cats
Common places to look for ticks

A veterinarian’s physical examination is often not the only thing needed to make a diagnosis; however, in pets showing signs, it will help your veterinarian know what tests to run.

A complete blood count, (CBC), may indicate a decrease in red blood cells (anemia), or a decrease in platelets (thrombocytopenia). Sometimes anaplasmosis can be diagnosed by finding the organisms in a blood sample by using a microscope.

Additional lab tests that specifically look for tick exposure or infection may be needed to confirm the diagnosis. Occasionally, these tests can be positive in a dog or cat who is not showing symptoms. This does not necessarily mean the pet has the disease, but it can mean that they were exposed to it at one point. 

Treatment and Recovery 

Anaplasmosis is treated with certain types of antibiotics, most commonly doxycycline. This antibiotic is  commonly used for 2-4 weeks; the longer course tends to be given if the pet also has Lyme disease, but it all depends on the specific case.

Pets usually feel better within a few days after taking the antibiotic. If the anemia or thrombocytopenia are severe, a blood transfusion may also be needed. Most cats and dogs make a full recovery when the disease is caught early on.


No vaccine is available to prevent anaplasmosis. The best form of prevention is tick control, either through treating the yard or through applying tick preventive medications to the pet. Consult your veterinarian for the best prevention options for each pet.

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