A woman checks her dog for ticks.

Anaplasmosis in Dogs

Anaplasmosis is a bacterial disease caused by the bacterium from the species Anaplasma (A. spp.). Variant species of Anaplasma are found worldwide, but the most common species in the United States is Anaplasma phagocytophilum. A. phagocytophilum invades the bloodstream and infects the white blood cells of the host.

Anaplasmosis is a vector-borne disease. This type of disease needs an intermediary living organism to be the middleman (or vector) in order for a pathogen to be transmitted from one animal or person to another. The vector for A. phagocytophilum is the Ixodes species (Ixodes spp.) of tick, which can be found globally. In the U.S., the blacklegged deer tick (Ixodes scapularis) is the most common member of Ixodes spp. This tick is found mainly in the upper midwest and northeastern states, which leads to a majority of cases popping up in those regions. Cats, horses, cows, and other ruminants are also susceptible to Anaplasma infection, but cases are significantly less common than those in dogs.

Anaplasmosis is a reportable disease, meaning that government officials deem it to be of great public health importance. By law, doctors must report any confirmed or suspected cases. By gathering information on the number and geographical location of cases, public health officials can monitor the disease and attempt to provide early warning of potential outbreaks.

Transmission of Anaplasmosis

A. phagocytophilum is transmitted when an animal or person is bitten by a tick that is infected with the bacteria. Infection can occur at any time of the year, however, most cases are reported from June to November, when people are out hiking and enjoying nature.

Ticks live in long grasses and wooded areas, so spending time outside can put you and your pet in contact with ticks. They must feed on blood during every point of their life cycle to survive and are constantly looking for their next meal. They lay in wait on the tips of grasses and plants and detect body heat. When a host brushes past, the tick climbs aboard and attaches. The tick then bites the skin and inserts a feeding tube to extract blood from their host. They will stay attached until they’ve had their fill. At this point, a pathogen can be transmitted from the tick to the current host, or the tick can acquire a pathogen from an infected host that it can pass on to its next host. Once a tick has finished its blood meal, it will drop off and begin to look for the next host. Ticks must be attached to a host for 24 – 48 hours to transmit disease.

The bacteria is most commonly transmitted by the nymph or juvenile stage of the tick. Due to their miniscule size, they may be difficult to spot and it may be hard to detect a bite.

Clinical Signs

The clinical signs of anaplasmosis typically present 1 – 2 weeks after a tick bite, and are similar to Lyme disease (which is also a tick-borne illness). Blood tests must be run to come to a definitive diagnosis. The blacklegged deer tick is also the disease vector for Lyme disease and dogs can be infected with anaplasmosis and Lyme disease concurrently.

Many infected dogs do not show any sign of disease. If symptoms are seen, they are often very vague and commonly include:

Less common signs include:

The disease tends to be self limiting and most dogs will only show symptoms for 1 – 7 days. Dogs who are very young, elderly, or who have a compromised immune system may be at risk for more serious illness, which can include respiratory and clotting difficulties.


When you take your dog to the veterinarian, they will run blood tests to determine a diagnosis. A complete blood count (CBC) will be conducted, which checks the amount and quality of the parts of the blood, including red and white blood cells and clotting cells known as platelets. They will likely also make a slide of a small amount of blood, called a blood smear, which will be examined under a microscope.

Thrombocytopenia, a reduction in the normal number of platelets in the blood, is seen on the CBC of most infected dogs. This can be a dangerous deficiency, as it can cause slow clotting times and excessive bleeding or bruising from even small injuries. Dogs may often present with a bloody nose (epistaxis).

When inspected under a microscope, the blood smear will show the bacteria inside the white blood cells. This will indicate a high likelihood of anaplasmosis. A quick in-clinic test is available that will be run by your veterinarian if there is suspicion of a tick-borne disease. It is an enzyme-linked immunoassay test (ELISA). The ELISA measures antibodies in the blood, indicating that there has been an infection. It is a quick test that can provide accurate results in just a few minutes with a small amount of blood. Your veterinarian may also send blood to an outside lab to be analyzed to confirm the results of the in-clinic test.

Treatment for Anaplasmosis

Treatment for anaplasmosis concentrates on treating the symptoms of the disease and eliminating the bacteria from the body. This includes the use of antibiotics, pain relievers, and anti-inflammatories. Most animals will not need to be hospitalized.

The most common antibiotic to treat anaplasmosis is doxycycline. An animal will most likely be prescribed a 4-week regimen of this medication. Most dogs show a marked improvement of symptoms within 48 hours of starting the antibiotic, but it is important to finish the full regimen to ensure that the bacteria is completely eliminated from the body. If deemed necessary, your veterinarian will prescribe medication to treat any pain or stiffness. If your pet has uncommon symptoms, like vomiting or diarrhea, antinausea and antidiarrheals may also be prescribed. While some dogs have clotting issues, it is usually not necessary for them to receive a blood transfusion. The prognosis for dogs with anaplasmosis is excellent, if appropriate treatment measures have been taken and no long-term effects have been noted.


There is no vaccine available to prevent anaplasmosis, so the most effective prevention is to protect your pets from tick bites.

Preventative measures include:

Can I Get Anaplasmosis from My Pet?

Anaplasmosis is considered a zoonotic disease, meaning that it can be transferred from human to animal and from animal to human. Since the A. spp needs a vector to transmit, it is extremely unlikely that you will catch anaplasmosis from your pet. However, if you are taking your pet somewhere that it can be bitten by a tick, it is possible that you could also be bitten and contract the bacteria. Protect yourself in many of the same ways you protect your pet, including staying on marked trails, wearing long clothing when hiking or camping, using insect repellent, and checking for ticks after being in long grasses or wooded areas.