Page 1520 - Small Animal Internal Medicine, 6th Edition

1492 PART XIV Infectious Diseases

and prevalence rates vary greatly by region and the life- whether an FIV-seropositive cat with a concurrent infec-
style of the cats tested. FIV replicates in several cell types, tious disease has a poor prognosis is to treat the concurrent
VetBooks.ir including T lymphocytes (CD4 and CD8 ), B lymphocytes, infection.
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macrophages, and astrocytes. The primary phase of infec-
Primary (acute) FIV infection is characterized by fever
tion occurs as the virus disseminates throughout the body,
present FIV-infected cats in the immunodeficiency stage for
initially leading to low-grade fever, neutropenia, and gen- and generalized lymphadenopathy. Owners commonly
eralized reactive lymphadenopathy. A subclinical, latent evaluation of nonspecific signs such as anorexia, weight loss,
period of variable length then develops; the length of this and depression or for evaluation of abnormalities associated
period is related in part to the strain of virus and the age with specific organ systems. When a clinical syndrome is
of the cat when infected. The median ages of healthy, natu- diagnosed in a cat seropositive for FIV, the workup should
rally infected cats and clinically ill naturally infected cats are include diagnostic tests for other potential causes (see
approximately 3 years and 10 years, respectively, suggesting a Table 96.2).
latent period of years for most strains of FIV. Chronic experi- Clinical syndromes reportedly from primary viral effects
mental and naturally occurring infection results in a slow include chronic small-bowel diarrhea, nonregenerative
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decline in circulating CD4 lymphocyte numbers, response anemia, thrombocytopenia, neutropenia, lymphadenopathy,
to mitogens, and decreased production of cytokines associ- pars planitis (inflammation in the anterior vitreous humor),
ated with cell-mediated immunity, such as interleukin (IL)-2 anterior uveitis, glomerulonephritis, renal insufficiency, and
and IL-10; neutrophil function and natural killer cell func- hyperglobulinemia. Oral cavity inflammatory diseases occur
tion are also affected. Humeral immune responses are often in both FIV and FeLV infected cats (Kornya et al., 2014). In
intact, and a polyclonal gammopathy develops from non- one report of naturally infected cats, FIV was associated with
specific B-lymphocyte activation. Within months to years, proteinuria but not renal azotemia (Baxter et al., 2012). In
an immune deficiency stage similar to acquired immunode- another study, proteinuria and low specific gravity were
ficiency syndrome (AIDS) in human beings develops. Co- common in FIV-positive cats (Taffin et al., 2017). FIV may
infection with FeLV potentiates the primary and immune play a role in the development of hypertrophic cardiomyopa-
deficiency phases of FIV. However, co-infection with Myco- thy in some cats (Rolim et al., 2016). However, secondary
plasma haemofelis, Toxoplasma gondii, feline herpesvirus, infections associated with myocarditis like T. gondii and Bar-
and feline calicivirus, as well as immunization, failed to tonella spp. should also always be excluded in these cases.
potentiate FIV-associated immunodeficiency in research Behavioral abnormalities, with dementia, hiding, rage, inap-
studies. However, FIV antibodies and hemoplasma infec- propriate elimination, and roaming, are neurologic manifes-
tions are associated in some studies, which may just reflect tations of FIV infection. Seizures, nystagmus, ataxia, and
that both agents are transmitted directly (Sarvani et al., peripheral nerve abnormalities may occasionally be attribut-
2018). Recently, Felis catus gammaherpesvirus has been able to primary viral effects, but secondary infections associ-
be detected in FIV-infected cats, and the role co-infection ated with neurologic disease like T. gondii should always be
with the two viruses plays in pathogenesis or progression excluded as well (Power et al., 2018). Lymphoid malignan-
of disease is being studied (McLuckie et al., 2017). Infection cies, myeloproliferative diseases, and several carcinomas and
with FIV may be associated with T-cell lymphomas (Murphy sarcomas have been detected in FIV-infected, FeLV-naïve
et al., 2018). Many cats with FIV antibodies survive for years cats, suggesting a potential association between FIV and
after diagnosis, and in one study, there was no difference in malignancy; FIV-infected cats are at higher risk for the
long-term survival between cats that were or were not FIV development of lymphoma (Magden et al., 2011; Murphy
infected (Liem et al., 2013). However, cats with FeLV infec- et al., 2018).
tion or FeLV and FIV co-infections had significantly shorter
life spans than cats infected with FIV alone (Spada et al., Diagnosis
2018). The oral and rectal microbiota of FIV-infected cats Neutropenia, thrombocytopenia, and nonregenerative
varies from healthy controls, which may relate to chronic anemia are common hematologic abnormalities associated
diarrhea and stomatitis that develops in some infected cats with FIV infection. Monocytosis and lymphocytosis occur
(Weese et al., 2015ab). in some cats and may be caused by the virus or chronic
infection with opportunistic pathogens. Cytologic examina-
Clinical Features tion of bone marrow aspirates may reveal maturation arrest
Clinical signs of infection with FIV can arise from direct (i.e., myelodysplasia), lymphoma, or leukemia. A progressive
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viral effects or secondary infections that ensue after the decline in CD4 lymphocytes, a plateau or progressive
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development of immunodeficiency (Table 96.2). Most of increase in CD8 lymphocytes, and an inversion of the CD4 /
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the clinical syndromes diagnosed in FIV-seropositive cats CD8 ratio occurs in experimentally infected cats over time.
also occur in FIV-naïve cats, which makes proving disease A multitude of serum biochemical abnormalities is possible
causation difficult during the subclinical stage of infection. depending on what FIV-associated syndrome is occurring.
A positive FIV antibody test does not prove immunodefi- Polyclonal gammopathy can occur in some FIV-infected
ciency or disease from FIV and does not necessarily indi- cats. No pathognomonic imaging abnormalities are associ-
cate a poor prognosis. The only way to determine accurately ated with FIV infection.