Page 1539 - Small Animal Internal Medicine, 6th Edition

CHAPTER 97 Polysystemic Mycotic Infections 1511

neuritis and may result in glaucoma and blindness. Other In one feline case, H. capsulatum antigen was detected in
than depression, CNS signs are uncommon. serum but not urine. In dogs, the urine antigen assay has
VetBooks.ir Diagnosis been evaluated in several studies. In one study of 17 con-
firmed cases of histoplasmosis and 41 cases with other dis-
A variety of nonspecific clinicopathologic and radiographic
false-positive results (Cunningham et al., 2015).
abnormalities are associated with histoplasmosis. Normo- eases, there were 2 false-negative antigen assay results but no
cytic, normochromic, nonregenerative anemia is the most
common hematologic abnormality in both dogs and cats. Treatment
Neutrophil counts can be normal, increased, or decreased. Because of its effectiveness and minimal toxicity, itracon-
Unlike the other systemic fungi, H. capsulatum is occasion- azole is the initial drug of choice for dogs and cats with
ally seen in circulating cells, particularly on examination histoplasmosis (see Table 97.2). Animals should be treated
of a buffy coat smear; mononuclear cell infection is most for 60 to 90 days or until clinical evidence of disease has been
common, followed by eosinophils. Thrombocytopenia from resolved for at least 1 month. Amphotericin B can be used
disseminated intravascular coagulation or microangiopathic in animals with life-threatening disease or in those unable to
destruction occurs in approximately 50% of dogs and some absorb oral medications because of intestinal disease. Keto-
cats. Some affected cats develop pancytopenia from bone conazole and fluconazole are also effective in some animals.
marrow infection. Hypoproteinemia and increased activities However, ketoconazole has more adverse effects than itra-
of alkaline phosphatase and alanine aminotransferase occur conazole, and some cases that do not respond to fluconazole
in some infected animals. respond to intraconazole. The overall success rate for the
Lysis predominates in animals with bone infection; peri- treatment of histoplasmosis in cats was 33% in one study
osteal and endosteal new bone production occurs in some (Clinkenbeard et al., 1989). In another study, all eight cats
cases. In dogs with pulmonary infection, radiographic treated with itraconazole (5 mg/kg PO q12h) were eventu-
abnormalities include diffuse interstitial, miliary-to-nodular ally cured (Hodges et al., 1994). Pulmonary disease in dogs
interstitial disease; hilar lymphadenopathy; pleural effusion; has a fair to good prognosis, whereas disseminated disease
and calcified pulmonary parenchyma caused by chronic has a poor prognosis. In one study, clinical outcomes were
disease. In some dogs, massive hilar lymphadenopathy is similar for 17 cats treated with fluconazole and 13 cats
the only radiographic finding. Alveolar lung disease, tra- treated with itraconazole (Reinhart et al., 2012). Histoplasma
cheobronchial lymphadenopathy, and calcified lymph nodes capsulatum may develop resistance to fluconazole during
are uncommon in cats. Colonoscopic findings in dogs with treatment (Renschler et al., 2017) as documented for C. gattii
gastrointestinal infection include increased mucosal granu- (Sykes et al., 2017). Use of serum and urine antigen testing
larity, friability, ulceration, and thickness. has been used to monitor response to treatment or recur-
Several tests have been evaluated for the detection of cir- rence in one series of 15 cats and showed potential clinical
culating antibodies against H. capsulatum in the serum of utility (Hanzlicek et al., 2016).
dogs and cats, but the sensitivity and specificity are poor Administration of glucocorticoids with or without anti-
for all. Serologic diagnosis is unreliable and should be used fungal drugs lessened clinical signs associated with chronic
only to establish a presumptive diagnosis when the organ- hilar lymphadenopathy much more quickly than did admin-
ism cannot be demonstrated by cytology, histopathology, istration of antifungal drugs alone and did not result in dis-
culture, or PCR assay, and the clinical signs are suggestive seminated histoplasmosis (Schulman et al., 1999). However,
of the disease. if the infection is active, administration of glucocorticoids
Definitive diagnosis requires demonstration of the organ- may exacerbate clinical disease.
ism by cytology, antigen assay, biopsy, culture, or amplifi-
cation of specific DNA by PCR assay (see Fig. 97.6). The Zoonotic Aspects and Prevention
organism is found most frequently in rectal scrapings or biop- Like blastomycosis, direct zoonotic transmission from
sies from dogs with large-bowel diarrhea, in bone marrow infected animals is unlikely because the yeast phase is not
or buffy coat cells from cats with disseminated disease, and as infectious as the mycelial phase. Care should be taken
in other locations (e.g., lymph nodes, lung, spleen, liver, skin when culturing the organism. Prevention includes the avoid-
nodules). The organism has also been identified in pleural ance of potentially contaminated soil. Organism numbers in
and peritoneal effusions and in CSF. contaminated areas can be decreased by application of 3%
In one retrospective study, results of a urine antigen assay formalin.
were compared with standard diagnostic methods in 18 cats
with clinical signs and clinicopathologic findings support- Suggested Readings
ive of histoplasmosis (MVista Histoplasma Antigen EIA; Blastomycosis
www.miravistalabs.com). Antigen was detected in the urine Anderson JL, et al. Clinical and molecular epidemiology of veteri-
of 17 of 18 cats, suggesting this assay may be useful for nary blastomycosis in Wisconsin. BMC Vet Res. 2013;9:84.
diagnosing this disease in cats. However, in cats with ocular Baumgardner DJ, et al. Effects of season and weather on blasto-
histoplasmosis, false negative antigen test results occurred mycosis in dogs: Northern Wisconsin, USA. Med Mycol. 2011;
using serum, urine, and subretinal fluid (Smith et al., 2017). 49:49.