Page 946 - Clinical Small Animal Internal Medicine

884 Section 9 Infectious Disease

to rat neurons in culture and may play a role in neuro­ Diagnosis
VetBooks.ir logic disease pathogenesis. The neurologic disease is Complete blood count (CBC) abnormalities may include
more prevalent with certain isolates of the virus, which
may point to certain envelope protein sequences being
more toxic and/or relate to the ability of virus to replicate anemia, lymphopenia, and neutropenia. Thrombocy­
topenia may sometimes occur. Hyperglobulinemia is the
in the feline nervous system. most common biochemical abnormality. Proteinuria
may be seen in cats with glomerulonephritis.
Antibodies to FIV infection persist for life and thus
Epidemiology patient‐side ELISA antibody testing is recommended as
a screen for FIV infection. However, false‐positive and ‐
Feline immunodeficiency virus infection is common negative results may occur. If a kitten under 6 months of
around the world. The incidence of FIV varies (from 4% age is antibody positive, it should be retested after 60
to 47%) geographically, correlating with the percentage days, as maternal antibody could be the cause of the pos­
of free‐roaming and feral cats in the population. itive assay. If an animal is negative after a recent possible
exposure, it should be retested after 60 days, allowing
sufficient time for an active immune response to develop.
Signalment Tests used to detect antibody cannot distinguish between
infection and vaccination. Positive tests in healthy cats
Although it is possible for any cat to be infected with FIV, should be confirmed using ELISA from another manu­
free‐roaming, nonpure‐bred, sexually intact, mature, facturer, western blotting, or PCR. In cases where the
male cats are more likely to contract an FIV infection. vaccination history is not known, real‐time quantitative
This is largely due to cat bites being the primary mode of PCR should be considered, as this assay can detect a low‐
virus transmission. grade viremia, indicative of an active infection. However,
sensitivity and specificity of PCR are variable. PCR may
be negative due to low levels of viremia or mutations,
History and Clinical Signs and false‐positive results have been reported in vacci­
nated cats.
Acute clinical signs of the infection are generally mild
and often consist of the nonspecific signs of lethargy,
anorexia, pyrexia, diarrhea, and lymphadenopathy. Management
Generally, these clinical signs coincide with the viremia.
Once the viremia subsides, the virus appears to go into The best therapy for FIV is prevention. Keeping cats
a clinical latent phase, with virus not detected in the indoors and only allowing exposure to known FIV‐nega­
blood and the apparent absence of most clinical signs. tive cats is the best way to prevent the infection. The vac­
This clinical latent phase is of variable length but often cine for FIV is controversial, as efficacy is variable.
lasts for years, as the virus slowly suppresses the Additionally, using standard FIV screening assays, a vac­
immune system. The last phase of the infection is cinated cat currently cannot be distinguished from an
feline acquired immune deficiency syndrome (FAIDS). infected cat. Since shelters may not perform a confirma­
Clinical signs of FAIDS are the result of opportunistic tory assay on an animal that is found FIV positive by a
infections, various neoplasias, and/or neurologic dis­ screening assay, it is advised to microchip the cat at the
ease. Thus, clinical signs are variable depending upon time of vaccination with a chip whose data are linked to
how the immune suppression is manifested. Stomatitis vaccination status to assist shelter personnel in the inter­
is very common and can occur during any phase of the pretation of a positive result.
infection. Persistent diarrhea is also fairly common, as The use of the routine feline vaccines in FIV‐positive
is respiratory disease. Neoplasia is common in FAIDS, cats is controversial due to the suppressed immune system
with B cell lymphoma being the most frequent. of the FIV‐infected cat. Since it is best to keep infected cats
Neurologic signs such as behavioral changes, disrupted indoors to reduce the risk of FIV exposure to other cats,
sleep, impaired learning, paresis, and seizures have the exposure of the infected cat to other common patho­
been reported. A wasting condition has also been gens is also reduced, thereby decreasing the need for vac­
described late in the FAIDS phase of the disease. cination. Additionally, the duration of immunity to most of
Increased circulating immune complexes can result in the vaccinatable feline pathogens likely lasts for years. If
immune complex disease manifested as uveitis and the cat has been vaccinated earlier in life, protective immu­
glomerulonephritis. nity likely still remains. If, however, vaccines are to be used,