Babesia tests (PCR and IFA antibody titer) in dogs and cats
Babesiae are single-celled parasites that live inside red blood cells and are spread by ticks. A PCR looks for their DNA in the blood and can name the species; an antibody test (IFA) shows that the dog’s immune system has met them. Babesiosis can destroy red cells, so both results are read together with the blood count.
What it shows
Several species infect dogs. Babesia canis, a large species, is carried by Dermacentor reticulatus ticks in Europe; B. vogeli by the brown dog tick, mainly in warmer regions; small species such as B. gibsoni occur more sporadically in Europe. A tick usually has to feed for 24–48 hours before it passes the parasite on. B. gibsoni can also spread through bites between dogs, and any species through blood transfusion.
A form can show two lines:
- Babesia PCR — looks for the parasite’s DNA. It is more sensitive than a blood smear, especially in chronically infected dogs and carriers, and species-specific PCR tells the species apart, which matters to the vet.
- Babesia canis IFA titer — measures the dog’s antibodies by immunofluorescence. Antibodies appear only about two weeks after infection, so the test is often not useful in acute illness. Antibodies to one species may cross-react with others.
Finding the parasites in a stained blood smear confirms acute infection; in chronic infection and carriers they are rarely seen.
Higher than reference — what it may be a sign of
- PCR detected — Babesia DNA is present. In a dog with anemia and fever this supports babesiosis as a possible cause. Finding the parasite does not always mean it is causing the current illness: dogs can carry it without signs.
- Antibodies positive — the dog has met Babesia. In regions where babesiosis is common, being antibody-positive is not the same as being ill. Because of cross-reactions, a positive B. canis titer does not prove which species it was.
- Carriers — a dog diagnosed with Babesia is regarded as a lifelong carrier; illness can return, for example after removal of the spleen or when immunity is suppressed.
Lower than reference
- PCR not detected — the expected result, but false negatives cannot be fully excluded: in chronic infection and carriers the number of parasites in the blood is very low and comes and goes. Blood taken early in the illness gives the best chance.
- Antibodies negative — does not exclude acute babesiosis, since in the first two weeks antibodies may not have formed yet.
Whether to repeat a test or choose another one is the vet’s decision.
Look at together with
- Haematocrit — anemia from red cell destruction is the key finding.
- Reticulocytes — show whether the bone marrow is replacing the lost cells.
- Platelets — a low count is common; low albumin and raised globulins can also be seen.
- Ehrlichia and Anaplasma — other tick-borne infections that also lower platelets.
Units and conversion
Both results are qualitative and have no unit. PCR is reported as detected or not detected, often with the species named. The IFA result is a titer written as 1:N — the highest dilution of serum at which antibodies are still seen, so 1:320 means more antibodies than 1:40; the lab’s positive cut-off is printed on the form. 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 a titer below the lab’s cut-off or “negative”. A positive result is read together with the dog’s signs, the blood count and where it lives or has travelled; the vet decides on the next step.
Cats and dogs
In cats, babesiosis has only occasionally been seen in Europe, and the species and their ticks are still unknown; in the United States it has not been reported in domestic cats. Babesia felis causes illness in cats mostly in southern Africa. The B. canis titer is a dog test.
In dogs, B. canis commonly causes hemolytic anemia and a low platelet count; hemoglobin can sometimes appear in the urine. B. gibsoni tends to cause a chronic illness with severe anemia, and higher infection rates have been found in American pit bull and American Staffordshire terriers.
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.