Anaplasmosis in Cats

What is Anaplasmosis in Cats?

Anaplasmosis is a tick-borne illness. It’s more common in humans, dogs, and other animals, but cats do contract it in rare instances.

Cats develop anaplasmosis as a result of being bit by a tick that carries the Anaplasma phagocytophilum bacterium. As with some other tick-borne diseases, a tick must remain attached to your cat for more than 24 hours for the infection to be transferred.

According to the Centers for Disease Control and Prevention, anaplasmosis is found across the United States, but higher rates of the illness are reported in the Northeast, Midwest, and West Coast. It is found in areas where there is a high tick population. In the Northeast, infections are most common in May, June and October.

Symptoms of Anaplasmosis in Cats

Cats usually develop symptoms within a few days to a week after the tick bite. Clinical signs may include:

• Poor appetite

• Lethargy

• Fever

• Stiff, painful joints

• Limping or trouble walking

• Enlarged lymph nodes

• Bloody nose

• Dark bloody stool

• Bruising

• Wobbly gait

• Seizures

• Conjunctivitis

• Protrusion of the third eyelid (inside the eye)

Not all cats carrying the anaplasma bacteria will have symptoms. Rarely, those that have a strong immune system will get sick for a short period of time and then recover quickly.

Causes of Anaplasmosis in Cats

The bacteria are transmitted to cats by ticks that carry the disease. Infections are highest in the late spring and autumn, when both nymph and adult ticks are most mobile. Anaplasmosis is transmitted to cats 24 to 48 hours after the tick attaches to your cat.

Anaplasmosis is not contagious from cat to cat, but it is common that all cats in the same home will get the disease at once, due to the same tick exposure.

How Veterinarians Diagnose Anaplasmosis in Cats

Your veterinarian will obtain a full history, including when a tick bite might have occurred, and conduct a complete physical examination. If the vet suspects this illness, they will order blood tests and urine tests to investigate further.

Your veterinarian might be able to diagnosis anaplasmosis by examining a blood sample under a microscope and spotting the bacteria. This is not always possible, and often requires a clinical pathologist because the organism is difficult to visualize. In most instances, your veterinarian will be looking for blood tests to indicate that your cat has thrombocytopenia (fewer platelets) or anemia (fewer blood cells); these findings suggest an Anaplasma infection because the organism affects different cells in the blood.

Anaplasmosis can be confused with other illnesses that cause fever, lethargy, anemia, thrombocytopenia, stiff joints, or dark stool. One or more of the following laboratory tests is performed to confirm the diagnosis.

• Wright’s stain is a special stain used on a cat’s blood sample that is examined in a microscope. This helps your veterinarian differentiate blood cells, making an infection of the blood more apparent as it allows for the bacteria to be seen on the blood smear. This used to be the primary way that veterinarians diagnosed anaplasmosis.

• Immunofluorescent antibody (IFA) tests for antibodies in the serum of the blood that react with the Anaplasma organism. The serum is the part of the blood left behind when all of the cells are removed by centrifugation ( high-speed spinning of a blood sample). This test also uses a microscopic evaluation.

• Enzyme-linked immunosorbent assay (ELISA) is another blood test. Typically, this test will not become positive until at least 8 days post-infection. This is a common test for cats suspected of having a long-term case of anaplasmosis.

• Polymerase chain reaction (PCR) tests for the presence of Anaplasma DNA in a biological sample, usually whole blood in cats. It is a more sensitive test done without a microscope. Molecular detection by PCR is very useful to quickly identify this organism and confirm reinfection or carrier status. This is the most common way that anaplasmosis will be diagnosed by your veterinarian, who will send a blood sample from your cat to an outside laboratory for analysis.

Treatment of Anaplasmosis in Cats

If your cat has severe anemia or thrombocytopenia, they might need a blood transfusion. Most of the time, anaplasmosis is treated with an oral antibiotic such as doxycycline. This drug works well but it has been associated with a narrowing of the esophagus, so it’s important to give your cat at least 5 milliliters of water or food after each dose.

Cats generally feel better 24-28 hours after starting the antibiotic, but do not stop administering the medication. Closely follow the vet’s instructions and administer every pill provided to your cat. A typical course of antibiotics lasts 2 to 4 weeks. 

Recovery and Management of Anaplasmosis in Cats

With correct treatment, the prognosis for cats with anaplasmosis is good. If your cat doesn’t seem to improve within a few days of starting antibiotics, they should be tested for other vector-borne diseases such as Lyme disease.

Most cats make a full recovery from anaplasmosis, but your veterinarian will want to monitor them afterward to be sure that the infection has cleared. Expect to bring your cat in for checkups two months after finishing antibiotics; treatment is considered successful once your cat has had two to three consecutive negative tests.

To reduce your cat’s chances of developing anaplasmosis in the future, limit outdoor access, use preventive medications, and conduct daily tick checks. Year-round tick prevention should be part of your cat’s preventive care, especially if ticks are common in your area.

Cats can still get ticks even if they are on monthly preventive treatment. It’s best to check your cat often if you live in an area where ticks are prevalent and after your cat comes in from outdoors (if applicable). Ticks are typically found near a cat’s neck, head, or ears, and in the creases under their legs.