Page 359 - Problem-Based Feline Medicine

18 – THE THIN, INAPPETENT CAT 351

Classical signs—Cont’d Many of the clinical signs relate to the presence of con-
current disease such as toxoplasmosis or hemobar-
● Immunosuppression – abscesses, cat flu, tonellosis.
vomiting, diarrhea, neoplasia.
● Ocular signs – uveitis.
● Neurological signs – ataxia, behavioral
changes. Diagnosis
When clinical disease warrants evaluation for FeLV,
See main references on page 540 for details (The testing should be performed.
Anemic Cat). ● However a positive test does not prove that the
disease process is caused by the virus.
Clinical signs Diagnosis is usually based on the detection of viral
antigen (usually the p27 core protein) by immuno-
There are no “classical signs” in a FeLV infection.
assay. The ELISA test is recommended by the
A variety of clinical signs may be noted dependent
American Association of Feline Practitioners.
on the body system affected. No one clinical sign is
● Serum or plasma is preferred over whole blood
found in all cats with persistent viral infection.
when ELISA testing because there are reported to
The most consistent clinical signs are weight loss, be fewer false positives.
variable anorexia, lethargy and depression.
A positive result may indicate:
Early infection with the virus is usually characterized ● Transient viremia in the early viremic state; the
by submandibular lymph-adenopathy and fever. cat may become negative later if a successful
This usually resolves in several days to weeks. immune response is mounted.
● Persistent viremia; such cats are likely to develop
Pale mucous membranes, weakness and anorexia are
FeLV-related disease.
seen if the virus causes anemia or bone marrow sup-
● Discordant results (positive antigen test and nega-
pression. Hematological disease may be a primary viral
tive on virus isolation) may occur early in the
effect on the bone marrow or secondary (e.g. neoplastic
course of the infection or may indicate focal infec-
infiltration, hemobartonellosis)
tion with no virus present in the circulation.
Respiratory distress occurs if the virus leads to devel- ● False-positive result.
opment of an anterior mediastinal lymphoma with or
Confirmatory tests should be considered in cats
without pleural effusion.
with a positive ELISA result, especially if the cat is
Signs of vomiting, diarrhea, and weight loss may be asymptomatic.
evident if there is gastro-intestinal infiltration with ● Immunoflorescent antibody test (IFA) detects
malignant lymphocytes. p27 antigen within neutrophils and platelets.
– A positive result indicates that the bone marrow
Signs of liver or renal failure occur if these organs are
is infected and such cats are likely to be persist-
involved in lymphoma.
ently infected. The IFA test is considered more
Gingivitis/stomatitis. specific, although slightly less sensitive, than the
ELISA.
Ocular signs are relatively common, primarily uveitis,
● Virus isolation is considered the gold standard
although neuro-ophthalmic signs, such as anisocoria
test for confirmation of FeLV infection.
may occur.
● Polymerase chain reaction (PCR) assays have been
Various neurological signs may also be noted including recently developed, however testing protocols
ataxia and behavioral changes. require further validation.
Immunosuppression may cause recurrent bacterial Certain forms of diseases (abdominal visceral lym-
infections, especially subcutaneous abscesses, which phoma) may be negative for the virus, although FeLV
recur or fail to respond to appropriate therapy. may have played a role in their development.