Anaplasma tests (antibody and PCR) in dogs and cats
Anaplasmas are tiny tick-borne bacteria. One species lives inside neutrophils, another inside platelets. An antibody test shows that the animal’s immune system has met them; a PCR looks for their DNA in the blood and tells the species apart. Many infected dogs show no signs, so a result is always read together with the animal’s condition and blood count.
What it shows
Two species matter in dogs:
- Anaplasma phagocytophilum — lives in neutrophils and is carried by Ixodes ticks. It can cause fever, lameness, enlarged lymph nodes and spleen, and bleeding.
- Anaplasma platys — lives in platelets and is carried by the brown dog tick (Rhipicephalus sanguineus). It causes a platelet count that falls and recovers in cycles of about 1–2 weeks.
A form can show two lines:
- Anaplasma antibody — an in-clinic rapid test or a lab immunofluorescence test (IFA) that finds the animal’s antibodies. The tests do not tell the two Anaplasma species apart.
- Anaplasma PCR — looks for the bacteria’s DNA. It is usually detectable within the first week of infection, earlier than antibodies, and it is the only method that names the species.
Higher than reference — what it may be a sign of
- Antibodies positive — the animal has met Anaplasma. Antibodies can persist for many months, so a positive result does not show when the infection happened or whether it is active. Antibodies alone, with no signs of illness, are not regarded as a reason for therapy. Cross-reactions are possible: with Ehrlichia and, for A. phagocytophilum, with A. platys and some other bacteria.
- Rising titer — paired samples 2–4 weeks apart help show a fresh infection: the antibodies appear or rise between the two tests.
- PCR detected — generally confirms infection and shows the species. Infection is often subclinical, so a positive PCR in a dog without signs is read together with the blood count and history.
Sometimes the bacteria are seen in a blood smear as small clusters (morulae) in neutrophils or platelets; a smear finding is then confirmed by PCR, since A. phagocytophilum looks the same as Ehrlichia ewingii under the microscope.
Lower than reference
- Antibodies negative — a test within the first week or so after infection can be falsely negative; seroconversion may take 1–4 weeks. A second test 3–4 weeks later is usually needed to see it.
- PCR not detected — does not exclude infection: the number of bacteria in the blood may fall below the test’s limit, for example after antibiotics.
Whether to repeat a test is the vet’s decision.
Look at together with
- Platelets — a low platelet count is the most common blood count change; it appears 1–2 weeks after infection. With A. platys the count may fall in cycles.
- Neutrophils — the cells where A. phagocytophilum lives; its clusters may be seen inside them in a smear.
- Ehrlichia — shares ticks and cross-reacts in antibody tests, so the vet may look at both.
- Lyme disease — carried by the same Ixodes ticks as A. phagocytophilum.
Units and conversion
Both results are qualitative and have no unit. A rapid test is reported as positive or negative. An IFA result may be printed as a titer, 1:N — the highest dilution of serum at which antibodies are still seen; the lab’s cut-off is on the form. PCR is reported as detected or not detected, often with the species named. In the app these results are stored as text.
Reference range
The reference range is on your lab’s form: for PCR it is “not detected”, for the antibody test “negative” or a titer below the lab’s cut-off. A positive result is read together with the animal’s signs, the platelet count and, if needed, a repeat test.
Cats and dogs
In cats, A. phagocytophilum infection has been reported but is rare; dogs are by far the most affected species. Infected cats have shown lethargy, poor appetite, fever, enlarged lymph nodes, anemia and a low platelet count. Much less is known about anaplasmosis in cats than in dogs.
In dogs, infection is usually subclinical. Both species have also been reported in people, but a tick is needed for transmission, so the dog does not pass it on directly; questions about human risk are for a doctor. Infection can also spread through blood transfusion.
Add a lab form — Pet Tracker Space recognises the lines, keeps the form’s units and draws each indicator over time with your lab’s reference band.
Sources
This page explains what a lab value means. It is not a diagnosis and not a substitute for your veterinarian — only they can interpret results for your pet.