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"A continuous intermittent febrile disorder that remains undiagnosed following
routine historical, physical, and laboratory evaluation for two weeks."1
Normal body temperature is maintained at a
set-point determined by the hypothalamus. For felines this
temperature ranges between 100°F-102.5° F (37.8°-39.5°C). Elevation
in temperature above the normal range can result from factors
unrelated to disease such as increased
environmental
temperature, circadian fluctuations,
exercise, excitement, and recent meals. In these patients, the
hypothalamic set-point is unchanged and increased body temperature
results from increased heat gain, heat production, or impaired heat
loss.
In
the case of a true fever, the set-point is elevated and the body acts
to maintain itself at the new, higher set-point.
Fever is a common symptom in cats with infectious
diseases, but can also be associated with immune, inflammatory, and
neoplastic diseases.
Many times a thorough history and physical exam reveal additional
clinical signs that help diagnose the underlying etiology, but
occasionally fever is the only apparent symptom and, therefore, the
only clue that there is an underlying problem. In these cases
additional diagnostic testing is begun and may include a combination
of the following:
* Ophthalmic
examination
* Neurologic examination
* Felv/FIV test
* Complete blood
count
* Blood chemistry profile
*
Urinalysis
* Radiographs/ultrasound
In some cases the cause of the fever is not
readily apparent even after these routine historical, physical and
laboratory evaluations; in these instances
empirical therapy, usually with
antibiotics, may be instituted along with supportive care to combat
the dehydration and anorexia that often accompany fever. Other
therapies that may be considered depending the suspected underlying
etiology include trial treatment with antifungal medications,
anti-inflammatory medications (meloxicam, steroids), or pain
medications as indicated.
When a fever persists or reoccurs
despite empirical therapy and the underlying etiology remains unclear,
examinations and testing may need to be repeated and many times
additional testing will be required and may include:
*
radiographs
* ultrasound
* bone marrow
aspiration
* exploratory surgery and biopsy
* specialized serologic testing
* histoplasma antigen testing
“Although some patients with fever of
unknown origin may have uncommon infectious, inflammatory, or
neoplastic diseases, many patients are ultimately found to have an
unusual or early manifestation of a common disorder. Management of
fever of unknown origin demands flexibility, dedication, and
patience. Many diagnostic tests, including repeated tests, may be
necessary to reach a diagnosis and the process may be costly and time
consuming. A diagnosis can be reached in most cases and many causes
of fever of unknown origin may be treatable or even curable.”2
Fever itself is not usually harmful; in fact, it can decrease
multiplication of some organisms, activate host defense systems, and
increase the effects of some antibiotics. It can also be important
in disease assessment and therapeutic monitoring.
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