Feline Leukemia Virus (FeLV) Testing: Complete Guide¶
Feline leukemia virus (FeLV) is a retrovirus that causes immunosuppression, anemia, and lymphoma. Testing strategy hinges on one critical distinction: persistent vs transient infection.
Why p27 Antigen¶
FeLV testing targets the p27 core antigen, which indicates active viral replication. This is the clinically relevant state — persistent infection carries a poor long-term prognosis, while transient infection is cleared by an immune-competent cat.
When to Test¶
| Signal | Action |
|---|---|
| New cat / kitten intake | Screen (standard of care) |
| Sick cat with anemia/lymphoma/immunosuppression | Test |
| Pre-vaccination | Test (establish status) |
| Multi-cat household / breeding | Test all |
Result Interpretation¶
| Result | Interpretation |
|---|---|
| p27 antigen positive | Active infection — confirm before management decision |
| p27 antigen negative | No active infection detected |
Confirmation Protocol¶
A single positive should be confirmed to distinguish persistent from transient infection:
- Retest antigen in 6–12 weeks (persistent infection stays positive).
- PCR (proviral DNA) can distinguish regressive from progressive infection where available.
Critical: Never make a euthanasia or rehoming decision on a single unconfirmed positive.
FAQ¶
Can a cat clear FeLV? Yes — some cats mount an effective immune response and clear the infection (transient/regressive infection). This is why confirmation matters.
Should I test kittens? Yes, but maternal antibodies do not cause p27 positivity — a positive kitten is genuinely infected.
Case Study: The Shelter Cat¶
A 2-year-old stray cat is admitted to a shelter. Initial screening:
- FeLV p27 antigen: positive.
- Physical exam: normal; no clinical signs.
Management: Per protocol, the positive was not treated as a final diagnosis. The cat was retested at 12 weeks — the repeat p27 antigen was negative, indicating a transient infection that the cat's immune system cleared.
Lesson: A single positive FeLV antigen is a signal to confirm, not to euthanize or rehome. Persistent infection is confirmed only by a repeat positive or PCR — this distinction changes outcomes.
References¶
- Giselbrecht J, Jähne S, et al. Evaluation of a Revised Point-of-Care Test for the Detection of Feline Leukaemia p27 Antigen and Anti-p15E Antibodies in Cats. Viruses. 2024;16(4):553. PMID: 38675954
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Authored by: Migibio Clinical & Scientific Affairs, Guangzhou Magic Biotech Co., Ltd.
Reviewed by: Migibio R&D Quality Committee
Last updated: 2026-08-13
Disclosure: Migibio (Guangzhou Magic Biotech Co., Ltd.) is the manufacturer of the FIA680/FIA880 analyzers and FICT reagents referenced in this content. See our Editorial & Review Policy.