Bartonella PCR in cats and dogs
Bartonella are small bacteria that live inside red blood cells and the lining of blood vessels. Cats are the main natural carriers, usually without any signs; fleas spread the bacteria between cats. A PCR test looks for Bartonella DNA in blood or tissue — and because healthy cats are often positive, the result is read together with the signs.
What it shows
More than 22 Bartonella species are known. In cats the most common is Bartonella henselae, the cause of cat scratch disease in people. Cats pick it up mainly through fleas and infected flea dirt. Young cats under two years, cats with outdoor access, cats from multi-cat homes and cats without flea control carry it more often.
Most infected cats look healthy. The bacteria can stay in the blood for months and come and go: in experiments young cats had relapsing bacteraemia for up to 454 days. Disease is uncommon but can be serious — it includes infection of heart valves or heart muscle, bone, fluid in body cavities and enlarged lymph nodes, among others.
PCR detects the bacterium’s DNA. Culture is considered the gold standard, and culture combined with PCR, repeated tests or several sample types find it more often.
Higher than reference — what it may be a sign of
- “Detected” (positive) — Bartonella DNA is in the sample. This shows infection, not necessarily disease: a positive culture or PCR does not confirm bartonellosis even in a cat with fitting signs, because healthy cats in areas where it is common are often positive. The vet first looks for other causes of the signs.
- How common carriers are — CDC cites Bartonella in the blood of 30–40% of domestic and shelter cats; in other studies the share of cats with DNA in blood ranged from 2.4% of healthy cats in one study to about 40% in sick cats in another study.
- In a dog — Bartonella is more likely to cause illness than in a cat, so a positive result together with signs such as fever or heart valve disease weighs more.
Lower than reference
“Not detected” (negative) means no Bartonella DNA was found in this sample. Because the bacteria may be in the blood only at times and in small numbers, one negative PCR does not completely rule out infection. If suspicion remains, the vet may repeat the test, test another sample or combine it with culture.
Look at together with
- Bartonella antibodies — a different test. Antibodies show exposure, not current infection, and do not protect against new infection. The antibody test has a low positive but high negative predictive value: a negative antibody result helps rule infection out better than a positive one rules it in.
- Globulin and neutrophils — high globulin or a rise in neutrophils can accompany bartonellosis but are not specific to it.
- Echocardiogram — when heart valve or muscle involvement is suspected.
- Haemoplasma PCR — another blood infection that a vet may check when looking for the cause of fever or anaemia.
Units and conversion
This is a qualitative test, so the result has no unit. On the form it is written as “detected” / “not detected”, or “positive” / “negative”; some labs also name the species found, for example B. henselae. Antibody results are reported separately, often as a titre (1:N) — that is a different row. The app stores the wording printed on the form.
Reference range
The reference is on your lab’s form — for this test it is “not detected”. ABCD advises testing cats with suspected bartonellosis, healthy cats that donate blood, and cats living with people whose immune system is weakened; testing healthy cats otherwise brings no benefit. B. henselae can infect people; any question about a person’s risk is for that person’s own doctor.
Cats and dogs
Cats are the main reservoir of B. henselae. Infection is most common and lasts longest in cats under two years. Most carriers have no signs; when signs occur, they include a short fever and, less often, lethargy, swollen lymph nodes, red eyes or poor appetite.
Dogs can be infected with B. henselae and other Bartonella species and are more likely than cats to become ill. Signs include fever, infection of the heart valves or heart muscle, heart rhythm problems, enlarged lymph nodes and nosebleeds. Bartonella is a recognised cause of aortic valve endocarditis in dogs. For a sick animal, blood or tissue, such as a lymph node or a heart valve, can be sent for culture or PCR.
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.