Anaplasmosis in Cats: Symptoms, Diagnosis, and Treatment

Name: Anaplasmosis in Cats: Symptoms, Diagnosis, and Treatment
Creator: Dr. Zubair Khalid

By Dr. Zubair Khalid, DVM, MS, PhD · 2026-10-02

Anaplasmosis in cats symptoms are easy to miss because they look like many other illnesses. Most owners notice a cat that suddenly seems tired, stops eating, and feels warm to the touch. This article is educational and is not a substitute for veterinary diagnosis or treatment.

Quick Answer

Anaplasmosis is a bacterial infection spread mainly by tick bites, and it can make cats sick with fever, lethargy, and appetite loss [1].
It appears to be uncommon in cats compared to dogs, but researchers disagree on how often it truly happens [2][1].
Diagnosis usually starts with blood tests, and a blood smear or PCR test can help confirm the infection.
Treatment is an antibiotic prescribed by your veterinarian, with the dose calculated from your cat's weight and health.
Most cats improve with prompt treatment, but some need follow-up blood work to confirm the infection has cleared.

What Is Anaplasmosis in Cats?

Anaplasmosis is a disease caused by a bacterium called Anaplasma phagocytophilum. This bacterium lives inside certain white blood cells, specifically the neutrophil granulocytes, and it is spread through tick bites [1]. The ticks involved belong to the Ixodes group, the same ticks that carry Lyme disease [1].

When an infected tick bites your cat, the bacteria enter the bloodstream and settle inside those white blood cells. The immune system responds, and the cat can develop a fever and other signs of illness. The infection is called granulocytic anaplasmosis because of the type of cell it targets [1].

Anaplasma in cats is part of a group of tick-borne infections that veterinarians watch for in pets that go outdoors. It can also affect people, dogs, horses, and livestock, which is why tick control matters for the whole household [3].

Anaplasmosis in Cats Symptoms: What Owners Notice First

The signs of anaplasmosis in cats are not dramatic in most cases. In a group of seven infected cats from Germany and Switzerland, the most common findings were fever, lethargy, and anorexia (loss of appetite) [1]. Those three signs are what most owners report first.

Other signs can appear depending on how sick the cat becomes. Some cats develop lameness or joint pain, which can look like a sudden reluctance to jump or walk. Others may seem generally unwell without any single obvious problem.

Because these signs overlap with many other conditions, anaplasmosis is easy to overlook. A cat with a fever and no appetite could have a urinary problem, an infection, or something else entirely. If your cat shows vague signs like these, a veterinary visit is the fastest way to sort out the cause. You can read more about how other infections present in Urinary Tract Infection Symptoms Cats Treatment and Cat Skin Infection: Signs and Treatment Options.

Signs That Point Toward a Tick-Borne Infection

Fever that comes on suddenly
Lethargy or reluctance to move
Loss of appetite or complete refusal to eat
Weight loss over a short period
Lameness or stiffness that shifts between legs
Pale gums or unusual bruising in severe cases

Not every cat shows all of these. Some cats carry the bacteria without obvious signs, which is one reason the true number of cases is hard to pin down [2].

How Common Is Anaplasmosis in Cats?

How common is anaplasmosis in cats? The honest answer is that it is less common than in dogs, but it is not as rare as once believed. A large European study tested 1,015 cats and found Anaplasma phagocytophilum DNA in 76 of them, which is 7.5 percent [2]. That study also found infections were more common in Northern Europe than in Central Europe [2].

A separate study from eastern Türkiye found Anaplasma DNA in 78.5 percent of 93 shelter cats, though that was a very different population with heavy tick exposure [4]. The wide gap between these numbers shows how much location and lifestyle affect risk.

Researchers still debate whether cats are truly less susceptible to the bacterium or whether the disease is simply underdiagnosed [1]. Cats may clear the infection on their own more often than dogs do, or veterinarians may not test for it as frequently. Either way, if your cat has tick exposure and unexplained fever, anaplasmosis belongs on the list of possibilities.

Causes and Risk Factors

The main cause is a bite from an infected Ixodes tick [1]. These ticks live in wooded and grassy areas, and they are most active in warmer months. A tick usually needs to stay attached for many hours before it passes the bacteria along.

There is also evidence that other blood-feeding insects may play a role. A laboratory study looked at Stomoxys calcitrans, the stable fly, and found that it could carry Anaplasma phagocytophilum DNA and RNA after feeding on infected blood [3]. That study was done under controlled conditions, so it does not prove flies spread the disease to cats in real life, but it raises the possibility that ticks are not the only route [3].

Risk factors that raise a cat's chance of infection include:

Living in or visiting areas with Ixodes ticks, especially wooded regions [2]
Going outdoors unsupervised
Living in a shelter or multi-cat environment with heavy tick exposure [4]
Living in regions where the bacteria are known to circulate, such as Northern Europe [2]

Indoor cats have a much lower risk, but ticks can hitch a ride indoors on people, dogs, or clothing. A quick tick check after outdoor time is a simple habit that helps.

How Veterinarians Diagnose Anaplasmosis in Cats

Diagnosis is tricky because the signs are vague and the tests have limits. Your veterinarian will start with a full physical exam and a history of your cat's lifestyle, including any tick exposure.

Blood Work and the Anaplasmosis in Cats Blood Smear

Routine blood work often shows changes that suggest infection, such as low platelets or mild anemia. A blood smear lets your veterinarian look at the white blood cells directly under a microscope. In some cases, the bacteria can be seen inside the neutrophils, which is a strong clue.

The problem is that the bacteria are not always visible on a smear. The organism can be present in low numbers, and it may not show up on any given day. A normal smear does not rule out anaplasmosis.

PCR Testing

PCR testing looks for the bacterium's DNA in a blood sample. This is the most sensitive method and is what most reference laboratories use [2][4]. A positive PCR result confirms that the bacteria are present at the time of testing.

Antibody Testing

Antibody tests check whether your cat's immune system has responded to the bacteria. A positive result means exposure happened at some point, but it does not prove the infection is active right now. Your veterinarian will combine test results with your cat's signs to decide what is going on.

Test	What It Shows	Main Limitation
Blood smear	Bacteria inside white blood cells	Often missed when bacteria are few
PCR	Bacterial DNA in the blood	Confirms infection only at the time of the sample
Antibody test	Immune response to the bacteria	Cannot tell current infection from past exposure
Routine blood work	Low platelets, anemia, organ changes	Not specific to anaplasmosis

Anaplasmosis in Cats Treatment

Anaplasmosis in cats treatment centers on antibiotics. The drug most often used is doxycycline, which is effective against Anaplasma species. Your veterinarian will calculate the exact dose from your cat's weight and overall health, so never use leftover medication or a dose meant for another pet.

Treatment usually lasts several weeks. Give every dose on schedule and finish the full course even if your cat starts acting normal after a few days. Stopping early can allow the infection to return.

Supportive care matters too. A cat with a fever and no appetite may need fluids, appetite support, or short-term nursing care. Some cats need to stay at the clinic for a day or two if they are dehydrated or very weak.

If your cat is on other medications, tell your veterinarian. Doxycycline can interact with certain drugs, and your vet needs the full picture to choose the safest plan.

Recovery, Outlook, and Long-Term Management

Most cats respond well to treatment and improve within a few days of starting antibiotics. Fever drops, appetite returns, and energy levels climb back toward normal. Full recovery can take a week or two, depending on how sick your cat was.

Follow-up blood work is often recommended after treatment ends. Your veterinarian may repeat a PCR test to confirm the bacteria are gone, or check blood counts to make sure platelets and red cells have returned to normal. This step matters because a cat can look fine while the infection lingers.

Some cats have lingering joint stiffness or take longer to regain their usual energy. If your cat was already dealing with another illness, recovery may be slower. Talk with your veterinarian about what a realistic timeline looks like for your cat.

Long-term management focuses on preventing new tick bites. A cat that has had anaplasmosis once can be infected again. Consistent tick prevention and regular tick checks are the best protection.

Prevention

Prevention comes down to keeping ticks off your cat. Talk with your veterinarian about a tick preventive product labeled for cats. Never use a dog product on a cat, since some tick medications are toxic to cats.

Other practical steps:

Check your cat for ticks after any time outdoors, especially around the ears, neck, and between the toes
Keep your cat indoors when possible
Clear tall grass and brush near your home
Check dogs in the household too, since they can bring ticks inside
Ask your veterinarian about tick-borne disease risk in your area

If you find an attached tick, remove it carefully with fine-tipped tweezers, pulling straight out close to the skin. Wash the area and note the date. If your cat develops a fever or stops eating in the weeks after a tick bite, call your veterinarian and mention the tick.

Limitations and When to Contact a Veterinarian

No article can tell you what is wrong with your individual cat. Only a veterinarian who examines your cat can diagnose and treat anaplasmosis. Use the guidance below to decide how quickly to seek care.

Contact your veterinarian the same day if your cat:

Has a fever above 103°F
Has stopped eating for more than 24 hours
Seems weak, wobbly, or unwilling to stand
Has pale gums or unusual bruising

Go to an emergency clinic right away if your cat:

Has trouble breathing
Collapses or cannot be woken
Has a seizure
Shows severe bleeding from the nose, gums, or in the stool

Schedule a routine visit if your cat:

Has been lethargic for more than a day or two
Is eating less than usual
Had a tick attached recently and now seems off
Has shifting lameness or stiffness

When in doubt, call. A quick phone conversation with your veterinary team can help you decide whether your cat needs to be seen now or can wait until morning.

Frequently Asked Questions

Can indoor cats get anaplasmosis?

Yes, indoor cats can get anaplasmosis if a tick bites them. Ticks can enter the home on people, dogs, or clothing, so indoor cats are not completely protected. Keeping up with tick checks and talking to your vet about prevention is still worthwhile.

Is anaplasmosis contagious between cats?

No, anaplasmosis does not spread directly from cat to cat. The infection moves through tick bites, so an infected cat cannot pass it to another cat by contact. This means you do not need to isolate a cat that has been diagnosed.

Can anaplasmosis in cats go away without treatment?

Some cats may clear the infection on their own, but there is no way to predict which ones will. Waiting carries a risk of worsening illness, so veterinarians usually treat confirmed cases with antibiotics. Prompt treatment also lowers the chance of long-term problems.

How long does treatment for anaplasmosis last in cats?

Treatment typically runs for several weeks, and your veterinarian will set the exact length based on your cat's response. Give every dose on schedule and finish the full course. Stopping early can let the infection come back.

Should I test my cat for anaplasmosis if it never had a tick?

Testing is usually reserved for cats with signs of illness or known tick exposure. A cat with no symptoms and no tick history rarely needs testing. If your cat has unexplained fever or lethargy, ask your veterinarian whether tick-borne disease testing makes sense.

References

Granulocytic anaplasmosis in cats from central Europe and molecular characterization of feline Anaplasma phagocytophilum strains by ankA gene, groEL gene and multilocus sequence typing. Parasites & vectors, 2023.
Molecular Detection of Anaplasma phagocytophilum in Cats in Europe and Associated Risk Factors. Animals : an open access journal from MDPI, 2024.
Stomoxys calcitrans as a potential mechanical vector of Anaplasma phagocytophilum: assessment through original ex vivo feeding models. Parasite (Paris, France), 2026.
Molecular detection and characterization of Anaplasma phagocytophilum-related strains and Hepatozoon spp. in domestic cats in eastern Türkiye. BMC veterinary research, 2026.