Anaplasmosis in Dogs

Jessica Vogelsang, DVM
By Jessica Vogelsang, DVM. Reviewed by Lauren Jones, VMD on May 3, 2022

Finding a tick on your dog is upsetting for a number of reasons. First, it can be upsetting, especially when the tick has been feeding for a while and is engorged like a bloodsucking raisin. More importantly, ticks carry a variety of diseases that can be passed to both dogs and humans. While many people are familiar with Lyme disease, anaplasmosis is a lesser-known but also significant tick-borne disease that can affect both you and your dog. 

What Is Anaplasmosis?

Anaplasmosis is a bacterial disease that, in a dog, comes in two forms:

  • Anaplasma phagocytophilium infects white blood cells (this is the form that is also found in people).
  • Anaplasma platys infects a dog’s platelets, which are involved in blood clotting.

Anaplasma occurs through many regions in the United States and Canada, correlating to the presence of the species of tick that transmit the disease. The areas with greatest incidence of canine anaplasmosis are the northeastern states, Gulf states, California, upper Midwest, southwestern states, and mid-Atlantic regions. 

According to the Companion Animal Parasite Council (CAPC), the incidence of anaplasmosis will likely continue to follow the expanding range of the deer tick in 2022. The Northeast and upper Midwest will likely see the most positive cases. CAPC also predicts many positive anaplasma cases in some regions of Virginia, West Virginia, and Texas.

How Is Anaplasmosis Transmitted?

Anaplasma platys is transmitted by the brown dog tick. Anaplasma phagocytophilium is transmitted by the deer tick and the western black-legged tick. Because the deer tick and the western black-legged tick are also vectors for other disease, it is not uncommon for dogs to be co-infected with multiple tick-borne diseases such as ehrlichiosis, Rocky Mountain spotted fever, and Lyme disease. There is no evidence that dogs can directly transmit the Anaplasma bacterium to people.

Anaplasmosis occurs worldwide in a wide number of mammals including dogs, cats, and people. Rodents are thought to be the reservoir for A. phagocytophilum while dogs are theorized to be the reservoir for A. platys. In both cases, while mammals are the reservoir, ticks are the means of transmission.

What Are the Symptoms of Anaplasmosis?

Symptoms usually begin within one to two weeks of the initial tick bite and transmission. As the two main anaplasmosis organisms infect different types of cells, the symptoms vary depending on which organism has infected the dog.

A. phagocytophilium is the more common form of anaplasmosis. Symptoms are generally vague and non-specific, which can make diagnosis difficult as there is no one clear sign that makes one suspicious for the disease. In people, the most commonly reported symptoms are fever, headache, chills and muscle ache. While we can extrapolate how affected pets might feel, we are limited to what we can observe when describing what the symptoms of Anaplasmosis are in dogs. Reported signs include:

  • Lameness and joint pain
  • Lethargy
  • Inappetence
  • Fever
  • Less commonly: coughing, seizures, vomiting and diarrhea

A. platys infects the platelets and affect blood clotting. Therefore, signs of this form of anaplasmosis are related to the body’s inability to properly stop bleeding and include bruising and red splotches on the gums and belly as well as nosebleeds.

How Is Anaplasmosis Diagnosed?

Your veterinarian will begin by taking a full history of your dog’s health and performing a physical examination. Your veterinarian may also suggest a number of tests depending on their clinical suspicion of anaplasmosis. Pets who have a history of tick exposure, live in an endemic area, and have the appropriate signs are all considered at risk.

An examination of the blood is the first step to evaluate the blood cells and platelets. While the organism may occasionally be identifiable under the microscope, more accurate tests are performed in the laboratory. These tests include ELISA (enzyme linked immunosorbent assay), IFA (indirect fluorescent antibody) and PCR (polymerase chain reaction).

How Is Anaplasmosis Treated?

Anaplasmosis can be treated with the antibiotic doxycycline. The earlier in the course of disease the treatment begins, the better the outcome. Most dogs are treated for 14-30 days, though improvement is often seen within the first few days of treatment.

Even if your dog has improved clinically, it is essential to finish the entire course of antibiotics. The long term prognosis for dogs who have undergone a full course of treatment is excellent. It is unknown if some dogs become persistent carriers without showing clinical signs of disease; some dogs may continue to test positive for anaplasmosis even after treatment and appearing clinically healthy.

How Do I Prevent Anaplasmosis?

The best prevention includes stringent tick prevention. “Natural” tick prevention treatments are usually poorly effective, especially in highly endemic areas. A wide variety of effective spot-on treatments, oral medications and tick collars are available to best fit your dog’s needs; consult your veterinarian for the choice that is best for you.

Check your dog for ticks every day, being sure to check in between the toes, under the collar, behind the ears, and in the armpits. Use your fingers to run through your dog’s fur, feeling for bumps. Ticks vary from the size of a pinhead to the size of a grape; while usually dark brown or black, they turn grey after they have been attached and feeding for a period of time. Grasp the tick close to the skin using tweezers or a device specifically designed for tick removal. Dispose of the tick by placing it in alcohol or flushing down the toilet.

Prophylactic treatment with doxycycline after a tick bite is not common practice in veterinary medicine. Antibiotic treatment is reserved for clinically ill dogs that have tested positive for the anaplasma bacterium. However, many laboratories test ticks for the presence of diseases like anaplasma and Lyme. Therefore, after the tick is removed, you may submit the tick to these labs to know if it carries harmful diseases.

While anaplasmosis doesn’t get the same attention as other tick-borne diseases such as Lyme and ehrlichiosis, it remains a significant disease of dogs and is being diagnosed with increased frequency across the United States. It is important to remember that a dog diagnosed with one type of tick-borne disease may have other ones as well because of the shared vector.

While prevention of transmission through good tick control is the best way to keep your pet safe, it’s good news that we have an effective treatment available. If you think your pet may have been exposed to any tick-borne disease, let your vet know so he or she can get your dog back on track.

Jessica Vogelsang, DVM


Jessica Vogelsang, DVM


Jessica Vogelsang, DVM, is a person who loves too many topics to be able to stick to one descriptor: writing, dogs, communication, cats,...

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