Neospora caninum antibodies (IFA) in dogs and cats
Neospora caninum is a single-celled parasite related to Toxoplasma. Dogs are its definitive host and can also fall ill, most strikingly puppies with weak, stiffly extended hind legs. The IFA test measures antibodies in serum or cerebrospinal fluid: it shows that the dog has met the parasite, while illness is judged together with the signs and other tests.
What it shows
IFA (indirect fluorescent antibody test) detects antibodies against N. caninum; it is considered a gold-standard serological test in dogs. Antibodies usually become detectable 2–3 weeks after infection. The test can be run on serum or on cerebrospinal fluid.
Other tests the vet may add:
- ELISA — another antibody test.
- PCR — looks for the parasite’s DNA, for example in cerebrospinal fluid.
- Muscle biopsy — the parasite can be seen under the microscope; immunohistochemistry may be needed to confirm it, because Neospora looks like Toxoplasma.
Higher than reference — what it may be a sign of
- Positive titer — the dog has been exposed. CAPC considers a titer of 1:50 or higher positive for exposure. Antibodies confirm contact with the parasite, but not disease: they are found in clinically healthy dogs too, and subclinical infections are suspected.
- High titer — most dogs with clinical signs have titers of 1:200 or higher. Together with fitting signs this supports a presumptive diagnosis.
- Rising titer — a fourfold rise in paired samples taken 15–30 days apart points to active infection.
- Signs that prompt the test — in puppies, weakness and rigid extension of the hind legs; in adults, nervous-system signs such as tremors, paralysis or difficulty swallowing, or muscle inflammation.
Lower than reference
A negative result makes exposure less likely but does not rule out neosporosis. Some dogs with clinical signs are seronegative at the time of testing, and very early in infection antibodies may not have appeared yet. PCR has gaps too: in one study 58.1% of dogs had a negative PCR despite high titers. That is why antibody testing and PCR of cerebrospinal fluid are recommended together with the signs. Stool tests help little: oocysts are rarely found and look like those of related parasites (Hammondia).
Look at together with
- Toxoplasma — a related parasite that causes similar signs; it is tested separately, with its own antibody tests.
- Cerebrospinal fluid analysis and PCR — when there are nervous-system signs.
- Littermates — often more than one puppy in a litter develops signs, so the vet may check littermates for antibodies too.
Units and conversion
Results have no unit. IFA is reported as a titer — the highest dilution of serum, written 1:N, at which antibodies are still detected (the larger N, the more antibody) — or simply as positive or negative. In the app these results are stored as text.
Reference range
The reference range is on your lab’s form, where the lab states from which titer it calls a result positive. Diagnosis is most often presumptive, based on history, signs and positive serology or PCR; finding the parasite in tissue confirms it. The vet reads the titer together with the signs and, where possible, paired samples.
Cats and dogs
In cats neosporosis has been produced experimentally, but clinical infection is extremely rare. Antibodies have been found in some feral cats, at low rates and without signs. A Neospora test in a cat is therefore unusual and is ordered by the vet for a specific reason.
Dogs are the definitive host. They become infected mainly by eating tissues of infected animals, especially cattle placenta and fetal membranes, and an infected bitch can pass the parasite to her puppies, sometimes in more than one litter. Signs usually appear before 6 months of age and as early as 3 weeks; the hind legs are affected first. Disease is less severe in adult dogs and can be subclinical. The parasite is not considered zoonotic.
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.