Kirk's Current Veterinary Therapy XIII Small Animal
Practice
CVT Update: Feline Leukemia Virus pgs 281
Year Published: 2000
Dr. Alice M. Wolf, ACVIM, ABVP (Fe)
(One of the Internal Medicine Consultants on the
www.vin.com board.)
PATHOGENESIS OF FELV
Following infection, FeLV has a specific pattern
or replication that affects the results of FeLV testing and the
clinical signs that may be seen in an individual cat.
STAGE I: Days 2 - 4
Replication: In local lymphoid tissue (retropharyngeal, tonsil,
gastrointestinal mucosal).
Clinical Signs: None to mild viral (fever)
FeLV status: All tests negative at this time
Prognosis: Majority recover
STAGE II: Days 1 - 14
Replication: Few circulating lymphocytes and mononuclear cells (primary
Viremia)
Clinical Signs: None, or mild viral signs
FeLV status: Serum ELISA becomes positive, PCR may be
positive, (IFA, saliva, tears negative)
Prognosis: Most recover, possible latency (6-30 mo)
STAGE III Days 3 - 12
Replication: Systemic lymphoid centers (germinal centers)
Clinical Signs: None, or mild to moderate viral signs
FeLV status: Serum ELISA positive, PCR positive, (IFA, saliva,
tears negative)
Prognosis: Recovery for many, possible future lymphosarcoma
STAGE IV Days 7 - 21
Replication: Bone marrow stem cells, epithelial cells
Clinical Signs: Peripheral blood alterations, viral signs
FeLV status: Serum ELISA, PCR, bone marrow IFA positive
(peripheral-blood IFA positive or negative, saliva, tears negative)
Prognosis: Likely to progress to persistent infection
STAGE V Days 14 - 28
Replication: Marrow origin, general viremia
Clinical Signs: All associated hematologic and systemic FeLV signs
possible
FeLV status: Serum ELISA, PCR, bone marrow, and
peripheral-blood IFA positive (saliva, tears negative)
Prognosis: Persistent Viremia, recovery from this stage of
infection is rare
STAGE VI Days 28 - ?
Replication: Marrow Viremia, widespread epithelial and lymphoid
replication
Clinical Signs: Any associated with FeLV
FeLV status: Serum ELISA, PCR, BM and
peripheral blood IFA, ELISA on saliva and tears may be positive
Prognosis: Long term prognosis is grave, 83% of
cats die within 3.5 years in multicat households, longevity is
increased for single cats with good veterinary care.