Page 406 - Problem-Based Feline Medicine

398 PART 7 SICK CAT WITH SPECIFIC SIGNS

Mild to marked lymphadenopathy and various asso-
DISEASES CAUSING PERIPHERAL ciated signs may occur with other FeLV-associated
LYMPHADENOPATHY
disorders (e.g. neoplasia and fungal infection).

FELINE LEUKEMIA VIRUS (FELV) Diagnosis
INFECTION**
FeLV tests.
● ELISA, FA and rapid immunomigration (RIM)
Classical signs
tests detect p27 protein produced by the virus.
● Lethargy, inappetence, weight loss, – ELISA test may be weakly positive during pri-
unkempt haircoat. mary viremia; FA test is negative. Because pri-
● Fever, gingivitis, recurrent upper mary viremia may be terminated by an effective
respiratory infections, opportunistic immune response, the ELISA test should be
infections. repeated in 4–6 weeks.
● Anemia. – ELISA and FA tests are usually both positive
● Generalized lymphadenopathy may occur during persistent viremia.
in viremic cats. – RIM test results correlate closely to ELISA test
results.
See main reference, page 540 (The Anemic Cat). ● Some PCR tests are available to detect viral DNA.
PCR may be positive during primary viremia. PCR
is positive during persistent viremia, and is more
Pathogenesis
sensitive than either ELISA or FA. It should be
FeLV infection may cause solitary, regional and gen- noted that PCR testing has not been standard-
eralized lymphadenopathy by several mechanisms. ized and is more likely to give false-positive
These include: results than ELISA and FA if the laboratory
● Lymphoid hyperplasia during primary viremia (ini- does not maintain the highest standards of qual-
tial infection). ity control.
● Lymphoid hyperplasia during persistent viremia. ● If FeLV tests on peripheral blood are negative and
● Atypical hyperplasia. another cause of lymphadenopathy has not been
● Lymphoma. determined, obtain a FA or PCR test on a bone mar-
● Metastatic neoplasia. row or lymph node aspirate, or immunohisto-
● Immunosuppression causing bacterial infections chemistry test on a bone marrow core or lymph
(e.g. gingivitis/stomatitis, pyoderma) and fungal node biopsy.
infections (e.g. cryptococcosis), and reactive hyper-
Lymph node biopsy reveals follicular or paracortical
plasia or lymphadenitis.
lymphoid hyperplasia.
● Immune-complex diseases (e.g. polyarthritis) and
reactive hyperplasia.
Differential diagnosis
Clinical signs Lymphoma, metastatic lymphadenopathy, atypical
hyperplasia, and possibly hyperplasia from other
Mild to moderate generalized lymphadenopathy may causes may be distinguished from FeLV-induced hyper-
occur during primary viremia. plasia by lymph node histology.
● Cats may otherwise be normal or have variable
Lymphoma may be present at other sites – e.g. bone
lethargy, inappetence and fever.
marrow, liver, spleen.
Mild to moderate generalized lymphadenopathy
A primary tumor should be identifiable with metastas-
may occur during persistent viremia.
tic lymphadenopathy.
● Mandibular nodes may be more affected.
● Cats may otherwise be normal or have variable Signs of infections, skin diseases or immune-medi-
lethargy, inappetence and fever. ated disorders should be present if lymphadenopathy