Anaplasmosis in dogs: symptoms, tests and treatment

Overview

Anaplasma bacteria live inside a dog's cells. Anaplasma phagocytophilum infects neutrophils, a type of white blood cell. Its disease is called granulocytic anaplasmosis. Another species, Anaplasma platys, infects platelets. It causes periodic falls in platelet numbers. The species can produce partly similar general signs despite targeting different cells.

A study from northern Europe published in 2023 looked for bacteria in ticks removed from pet dogs and cats. Anaplasma phagocytophilum was found in 12 ticks, or 3.5% of those examined. There were 342 ticks in total. These findings concern bacteria in ticks, rather than the percentage of dogs becoming ill. A tick attached to a healthy dog can therefore also be an exposure source.

The northern European tick study collected samples at 10 veterinary practices. Across all pathogens tested, 17% of ticks carried at least one. The castor bean tick was the most common species collected. It accounted for 84.5% of examined ticks. Taiga ticks accounted for 14.9%.

Causes

Infection passes to a dog through a feeding tick. Bacterial transmission usually requires about 24–48 hours of attachment. Signs generally begin within 1–2 weeks of the bite. Nevertheless, remove a tick as soon as you find it; an estimated transmission time is no reason to wait.

Blood-borne Anaplasma infection can also pass through transfusion. The brown dog tick, Rhipicephalus sanguineus, has been associated with transmission of A. platys. In parts of northern Europe, the castor bean tick, Ixodes ricinus, and taiga tick, Ixodes persulcatus, pose risks to pets. Tick species and travel history therefore influence which pathogens the vet suspects.

Inflammation triggered by infection can reduce platelet numbers through both destruction and reduced production. Low platelets predispose to small haemorrhages and other bleeding. The disease therefore involves more than local irritation at the bite site.

Anaplasma-infected cells occur in the circulation and in sites such as the spleen, liver and bone marrow. In Europe, the castor bean tick transmits A. phagocytophilum.

Risk factors

Risk chiefly depends on how often your dog encounters infected ticks. Long grass, woodland undergrowth and leaf litter increase opportunities for tick contact. Inadequate tick prevention also increases exposure opportunities.

Tick numbers and range have increased in parts of northern Europe, including urban and suburban environments. Living in a town therefore does not remove risk. A travelling dog may encounter ticks in different seasons in different regions. The evidence cited here does not establish a reliable breed or sex predisposition.

Keeping your dog on paths reduces contact with dense vegetation favoured by ticks.

In Europe, A. platys infections occur particularly in countries with a Mediterranean climate. In colder countries, cases are diagnosed especially in animals imported from that region.

Typical symptoms

Infection without signs is common, so not every exposed dog seems ill. When signs develop, they may be vague and resemble many other diseases. Changes you may notice at home include:

• Fever and greater tiredness than usual.
• Reduced appetite or refusal to eat.
• Lameness and stiff movement.
• Muscle pain and reluctance to move normally.
• Vomiting or diarrhoea.
• Rarely, a nosebleed.

Some dogs also become dehydrated. Neck pain and seizures are uncommon signs. Examination may find enlarged lymph nodes or an enlarged spleen.

Less common signs may include coughing or laboured breathing. Joint pain is another possible sign of Anaplasma infection in dogs.

Complications and consequences

Low platelet numbers, or thrombocytopenia, are the most common blood count change. This often appears 1–2 weeks after infection. In A. platys infection, platelets may fall and rise in 1–2-week cycles without treatment. This can make assessment from one blood sample difficult.

A severely affected dog should also be investigated for concurrent tick-borne infections. The outlook for a treated dog with signs is usually good. Treatment does not provide reliable protection against reinfection. Signs can return after new tick exposure.

Anaplasmosis often resembles Lyme disease, and a dog may have both infections together. They occur in the same regions because the same tick species transmit them. Finding Anaplasma antibodies therefore does not rule out another cause of lameness or fever.

Diagnosis at the vet

Diagnosis combines signs, blood results and infection tests. The blood count particularly assesses platelet numbers. An antibody test measures the body's response to the bacterium. A positive result may reflect past exposure rather than active disease. Antibodies can remain in the blood for months after infection.

An antibody test may still be negative during the first 1 week after infection. Antibodies are checked in another sample after 2–4 weeks when needed. Antibody testing also does not distinguish different Anaplasma species.

PCR looks for bacterial genetic material in a blood sample, for example. Genetic material may be detected during the first week after infection. PCR also allows identification of the Anaplasma species responsible. The aim is to sample as early as possible and before antibiotics begin.

Antibiotics already started can reduce bacteria in the blood and make PCR negative. A naturally low bacterial count may also fall below the test's detection limit. A negative result is therefore interpreted according to sampling time and the wider situation. A blood smear may show bacterial clusters, called morulae, in neutrophils or platelets. However, these are often difficult to find even during acute illness.

A morula in a neutrophil does not reliably distinguish Anaplasma from Ehrlichia ewingii infection. Laboratory method choice is therefore particularly important when several bacteria targeting blood cells are suspected in a travelled dog.

Detectable antibodies can take 1–4 weeks to form after exposure. In practice, paired samples are often taken 3–4 weeks apart. Antibody tests may cross-react with other bacteria, such as A. platys. A smear from the sample's white blood cell layer may improve detection of morulae. A positive microscopic finding is recommended to be confirmed by PCR.

Treatment

The vet prescribes treatment and medicines. Anaplasmosis causing signs is usually treated with the antibiotic doxycycline. Dogs often begin improving within 1–2 days of starting treatment. In most, signs resolve during the first 1 week after antibiotics begin. Continue treatment according to the veterinary plan; rapid improvement is not an instruction to stop medication.

A positive antibody test alone, without signs or blood count changes, does not require antibiotics. Other blood results are therefore also checked when assessing treatment need. Monitoring may include further tests to confirm diagnosis. If suspicion arises only from screening, the result does not automatically mean your dog currently has a feverish illness.

The vet may prescribe pain relief when needed. A dehydrated or otherwise unwell patient may also need fluids. Some cases involve an immune-mediated inflammatory response. A corticosteroid and other supportive care may then be necessary. Most mild cases do not need extensive supportive care.

If doxycycline is unavailable, the vet may choose minocycline instead. In some cases, bacteria may persist despite treatment. When signs recur, both reactivation of an old infection and reinfection are assessed. Tick prevention is also reviewed in a dog that has tested positive.

Doxycycline belongs to the tetracycline antibiotics used for anaplasmosis. Unnecessary antibiotic courses can promote resistance and make later treatment less effective. A clinically recovered dog may still have a positive antibody test. Another course is not usually given simply to make the test negative.

Prevention

There is no anaplasmosis vaccine for dogs. Prevention relies on reducing tick exposure and suitable tick medication. Choose a product suited to your dog and use it according to the instructions. Coat checks alone do not provide complete protection because not every tick is found in practice.

Check your dog's coat after walks and remove ticks promptly. Keeping grass and shrubs short in the garden reduces habitats favoured by ticks. Removing leaf piles is another preventive measure. Avoid dense undergrowth and long grass in tick areas.

Remove a tick with tweezers or a purpose-made removal tool. Avoid contact with its contents, using gloves if necessary. Wash your hands afterwards. Do not give a dog-only tick product to a cat. Garlic does not stop ticks attaching. It can also cause anaemia in dogs.

Important for dog owners

Record the date a tick was found, any travel and when signs first appeared. Bring details of tick prevention and all medicines to the appointment. Mention antibiotics started before blood sampling, as they may affect PCR results. At home, watch appetite, alertness, movement and any bleeding. Agree with your vet which blood values need rechecking and when to report your dog's condition again.

Anaplasmosis can also make humans ill. However, it does not spread directly from dogs to people. A dog can still bring ticks indoors on their coat. Check your own skin and clothing after walks too. Remembering tick exposure helps interpret later signs, but diagnosis requires examination of your dog.

Frequently asked questions

Does a positive test mean my dog is ill?

Not necessarily. Antibodies can remain in the blood for months after a previous infection. A symptom-free dog with a normal blood count does not need antibiotics solely because of an antibody result. The vet decides on further investigations from the result and overall circumstances.

Can the test be negative at first?

Yes. Antibody testing may be negative during the first 1 week after infection. Another sample after 2–4 weeks can then help assessment. PCR can detect bacterial genetic material in blood very early in infection.

How quickly do antibiotics help?

Many dogs with signs begin to brighten within 1–2 days of starting medication. In most, signs disappear during the first 1 week. Nevertheless, complete the prescribed treatment. Contact your vet again if improvement does not occur as expected.

Can my dog become ill again?

Yes. Reinfection is possible when an infected tick attaches. Previous illness does not appear to provide protective immunity. Continue tick control after successful treatment. A positive result is also an opportunity to review how well current protection works.

Can my dog give me anaplasmosis?

Direct transmission from dog to human does not occur; a tick is needed. However, your dog can bring ticks indoors. Check both your dog's coat and your own skin after walks. Good tick protection for your dog reduces shared exposure.