Leishmania tests (IFA antibodies and PCR) in dogs and cats
Leishmaniosis is a parasitic disease caused by Leishmania infantum and spread mainly by sand flies. Many infected dogs never become ill, so a result is read together with signs and other blood work. Two lines appear on forms: IFA measures antibodies against the parasite, and PCR looks for the parasite’s DNA.
What it shows
Leishmania infantum occurs across the Mediterranean basin, Africa, parts of Asia and the Americas, and is increasingly found in countries where it is not native, mostly in imported dogs. Besides sand flies it can pass from mother to puppies, through mating and through blood transfusion. In regions where it is common, usually 5–30% of dogs are infected, and more than 60% in some areas, yet only about 10% of infected dogs show signs. The incubation period can last months to years.
- IFA (indirect immunofluorescence) for antibodies — a quantitative test: the serum is diluted step by step and the result is the highest dilution at which antibodies are still detected. It shows the immune response to the parasite, not the parasite itself.
- Leishmania PCR — looks for the parasite’s DNA in a sample. How useful it is depends heavily on which tissue is sent.
Higher than reference — what it may be a sign of
- High antibody levels in a dog with fitting signs and lab changes are regarded as conclusive for leishmaniosis.
- Low positive titer — not enough on its own: infection is confirmed by other methods, such as cytology, histology or PCR. Antibodies can cross-react with other Leishmania species and with trypanosomes (Trypanosoma cruzi where it occurs), and some vaccines against leishmaniosis produce antibodies that certain tests detect — the vaccination history matters.
- PCR detected — the parasite is present, that is, the animal is infected. Infection is not the same as disease: many infected dogs stay healthy. For an apparently healthy, unvaccinated dog with positive PCR and negative antibodies, the LeishVet recommendation is monitoring every 3–6 months for antibodies and signs.
- A titer rise of at least 2–3 dilutions on follow-up is read as a marker of relapse; a fall of at least 2–3 dilutions can accompany clinical improvement within 6–12 months.
Lower than reference
A negative or low antibody result does not exclude infection: infected dogs without signs may have no or low antibody levels — finding infection in them may need both antibody testing and PCR — and cats tend to have weaker antibody responses than dogs. A negative PCR on blood or urine means little on its own, because these samples are much less sensitive than bone marrow, lymph node, spleen or skin. Testing two or three samples from different tissues is recommended. If the picture still fits, the vet may repeat the test or choose another method.
Look at together with
- Globulins, albumin, A/G ratio — high total protein with high globulins, low albumin and a lower A/G ratio are the most consistent chemistry changes.
- Protein electrophoresis — shows a polyclonal rise of beta and/or gamma globulins.
- Hematocrit — a mild to moderate non-regenerative anemia is common.
- UPC and creatinine — the kidneys are often involved; both are used to stage the disease.
Units and conversion
Neither line has units. IFA is reported as a titer 1:N — the highest dilution at which antibodies are still found; the larger N, the more antibodies — or as positive/negative, with the lab’s cut-off. PCR is reported as detected or not detected; quantitative PCR may also give an amount. In the app both are stored as text.
Reference range
The reference range is on your lab’s form: for PCR it is “not detected”, and for IFA the lab states which titer it considers negative, low positive and high positive. This split matters, because low and high positives are read differently. Leishmaniosis is a zoonosis; questions about the risk for people belong with a doctor for humans.
Cats and dogs
Cats get infected less often than dogs in the same area. The most common findings are skin or mucocutaneous lesions and enlarged lymph nodes; the most common lab change is high gamma globulins. Because cats tend to make fewer antibodies, a negative or low result in a cat with fitting signs leads to cytology, histology or quantitative PCR. Cats with FIV or FeLV are more likely to have antibodies, so cats suspected of leishmaniosis are also tested for FIV and FeLV.
Dogs are the main reservoir of the parasite. Most infected dogs stay without signs for a long time, which is why finding infection in a healthy dog — before import or blood donation, for example — may need both quantitative antibody testing and PCR. Marked high globulins without another cause in a dog from an endemic region are compatible with leishmaniosis.
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.