Regressive FeLV infection: what it means for the cat
Healthy 3-year-old domestic shorthair proposed as a blood donor. The FeLV p27 antigen test is negative, but the blood provirus PCR is positive.
Which statement is correct?
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A. It is a false-positive PCR of no clinical relevance; he can donate
With a negative antigen, a positive provirus PCR usually indicates genuine regressive infection. Ignoring it can transmit FeLV to the transfusion recipient.
B. He has a progressive infection and a life expectancy of 2–3 years
Progressive infection involves persistent viraemia, i.e. repeatedly positive p27 antigen. This cat has no antigenaemia.
C. He has a regressive infection: the provirus is integrated in the bone marrow; he does not usually shed virus, but can transmit FeLV by transfusion and reactivate with immunosuppression
Correct. The cat contained the viraemia but did not eliminate the virus. His prognosis is good and he rarely infects other cats, but he must not donate blood and unnecessary immunosuppressants should be avoided.
D. He has an abortive infection: he has completely eliminated the virus
In abortive infection no provirus is detected (negative PCR); only antibodies to the virus are present. A positive provirus PCR rules out this state.
lightbulb Key takeaway
FeLV states: abortive (antigen and provirus negative), regressive (antigen negative or transient, provirus positive) and progressive (persistent antigen and provirus positive). Test blood donors with both antigen and provirus PCR. A regressive cat may reactivate infection with corticosteroids, chemotherapy or severe illness.
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Updated: October 31, 2026 · Educational content for veterinary professionals. It does not replace current clinical guidelines or the judgement of the attending veterinarian.