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Coccidioidomycosis 185

• The mycelial/hyphal form of Coccidioides, ○ After inhalation, arthroconidia enter the • Thoracic radiographs are frequently abnormal
which grows in vitro and in nature is highly pulmonary alveoli and cause subpleural and are indicated for any suspect patient.
VetBooks.ir significant risk to laboratory personnel and ○ After infection of the respiratory system, interstitial or nodular interstitial pattern Diseases and Disorders
○ Common findings include a diffuse
lesions.
infectious by the aerosol route; cultures are a
the fungus changes morphology, forming
should be performed only in well-equipped
and hilar lymphadenopathy, which may
microbiology laboratories with trained
be profound.
personnel. spherules containing endospores in tissue. ○ Alveolar infiltrates, miliary interstitial pat-
The spherule releases endospores that can
disseminate after phagocytosis and form terns, or nodules with or without pleural
GEOGRAPHY AND SEASONALITY new spherules. This, together with the effusion or evidence of pericardial effusion
• Coccidioidomycosis occurs mainly in the pyogranulomatous inflammatory response, may be seen.
southwestern United States, including the results in clinical illness. ○ Spontaneous pneumothorax has been
central valley of California (Coccidioides ○ The incubation period from the time of described.
immitis); southern regions of Arizona, inhalation to the appearance of respiratory • Radiographs of long bones may reveal
Nevada, Utah, and New Mexico; and western signs is typically 1-3 weeks, but sometimes mixed proliferative and lytic lesions, typi-
Texas (Coccidioides posadasii). Disease has months. In some cases, infection may be cally located distally on long bones (distal
also emerged in south-central Washington present for years before causing overt signs. diaphysis, metaphysis, epiphysis). Biopsy
state. To a lesser extent, it occurs in regions Immune-complex glomerulonephritis has or cytology is necessary for a definitive
of Mexico and Central and South America been described in some dogs with chronic diagnosis.
(particularly Venezuela). Having lived in or coccidioidomycosis. • Magnetic resonance imaging of the CNS
traveled through these regions up to several • Disease may remain localized to the often reveals single focal lesions that may be
years before the onset of illness is almost respiratory tract or become systemic with extraaxial or intraaxial. Typically, lesions have
always a component of the history. dissemination to lymph nodes, bones, eyes, indistinct borders and vary in signal intensi-
• Because the disease is acquired through skin, pericardium, spleen, liver, kidney, testes, ties and the degree of contrast enhancement.
inhalation of airborne spores, the incidence and central nervous system (CNS).
increases after soil disturbance (dust storms, • As in humans, many animals develop Advanced or Confirmatory Testing
earthquakes, construction). transient, subclinical infections, and some • Coccidioidomycosis can be definitively diag-
may recover from localized respiratory illness nosed by cytologic examination of exudates,
Clinical Presentation without developing disseminated disease and sputum, or aspirates or by histopathologic
HISTORY, CHIEF COMPLAINT without therapy. examination of tissue.
• Chronic cough (pulmonary or hilar lymph ○ Approximately 28% of dogs living in an ○ Spherules are large (1-10 times the diam-
node involvement) may be dry and harsh endemic region develop antibodies to eter of a red blood cell), round structures
or moist and productive. Severe pulmonary Coccidioides spp by the age of 2 years, with a distinct cell wall typically sur-
involvement may be associated with respira- but only about 6% develop clinical rounded by neutrophils and macrophages.
tory distress. infection. ○ Transtracheal washes and lymph node aspi-
• Other presenting complaints include rates are often falsely negative. Cytologic
inappetence, weight loss, lethargy, lame- DIAGNOSIS evaluation of fluid from draining tracts or
ness, cutaneous masses with or without of pleural effusion is more likely to yield
draining tracts, signs of head or neck Diagnostic Overview organisms, which appear on Romanowsky
pain, signs of vision loss, or neurologic A definitive diagnosis of coccidioidomycosis is stains (e.g., Diff-Quik) as sometimes
signs such as seizures and ataxia. Dogs made by cytologic or histologic visualization crinkled, deeply basophilic structures.
with pericardial involvement may present of the organism in tissues. If the organism ○ Organisms can be difficult to find histo-
with signs of right-sided heart failure or cannot be identified, the diagnosis is based on pathologically but when present are readily
restrictive pericarditis. compatible presentation and results of serologic identified by their distinct morphology. In
• Skin lesions are uncommon and usually a tests. lesions with low numbers of organisms,
manifestation of disseminated disease rather periodic acid–Schiff and silver stains may
than a primary localized infection. Differential Diagnosis assist in identification of spherules.
• Cough (p. 1209) • Several canine and feline serologic tests are
PHYSICAL EXAM FINDINGS • Bone lesions: bacterial osteomyelitis, other available for immunoglobulin M (IgM)
Harsh breath sounds, cough, dyspnea, and fungal infections, bone neoplasia and IgG. Serologic tests may be positive
tachypnea are common. Systemic signs may • Skin lesions: draining tracts due to other in subclinically infected dogs. The agar gel
include fever, lethargy, and weakness. Lame- systemic mycoses, nocardia, actinomycosis, immunodiffusion assay (AGID), which detects
ness may be noted ± firm swellings over long or mycobacterial infections, bony lesions IgM and IgG, is most commonly used.
bones. Cutaneous masses with or without such as infected sequestra, abscesses due to ○ A positive IgM titer (tube precipitin
draining tracts may be present. Other findings bite wounds or other penetrating injuries, antigens) can be noted within 2 weeks
include lymphadenopathy, cranial and cervical or neoplasia of exposure (i.e., during or just after the
hyperesthesia, ascites, and signs of uveitis, focal • Ocular lesions: other systemic infectious incubation period) and may last 4-6 weeks.
chorioretinitis, or panophthalmitis. illnesses and immune-mediated diseases ○ A positive IgG titer (complement fixa-
tion [CF] antigens) indicates exposure or
Etiology and Pathophysiology Initial Database infection. The magnitude of the titer
• Coccidioides spp are dimorphic fungi; they • CBC may reveal an inflammatory leukogram is considered important, higher titers
exhibit different forms in tissues and in the with a monocytosis and a mild nonregenera- (≥1 : 64) are most consistent with clinical
environment. tive anemia. disease. Titers ≤ 4 may be consistent with
○ The mycelial form exists in soil and • Hypoalbuminemia (almost all cases) and previous exposure and recovery.
produces arthroconidia that are dispersed hyperglobulinemia (≈50% of cases) are ○ IgG titer is expected to decrease slowly
by wind and other disruption of the soil common. Hypercalcemia has not been but may not reach zero with successful
and easily inhaled. described in dogs or cats with coccidioido- treatment.
○ Inhalation of 10 or fewer arthroconidia is mycosis but does occur in people. ○ Positive IgG titers from dogs living in
sufficient to cause infection that produces • Urinalysis is usually unremarkable, but some endemic areas are more likely due to
clinical signs. dogs may have proteinuria. exposure than from active infection.
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