Veterinary Medicine - May 2008 - (Page 256) Histoplasmosis PEER-REVIEWED from pus and paraf n-embedded tissue samples of dogs with histoplasmosis.64,65 PCR testing is not commercially available for diagnostic testing for histoplasmosis in cats and dogs. Serology In people, standard serologic tests include complement xation and immunodiffusion, which use yeast and my- celial antigens to detect antibodies against H. capsulatum.61 Complement xation is more sensitive.62 However, when complement xation was performed in nine cases of canine histoplasmosis, only one titer of 1:8 was obtained.9 Similarly, serologic testing performed in nine cats with histoplasmosis had positive results in only four of the cats (44%).1 Because of a myriad of false negative and false positive results, serology for antibody detection is not considered a reliable method of diagnosis in cats and dogs.10,11 Antigen detection tests are used to detect histoplasmosis in human serum, urine, bronchoalveolar lavage uid, and cerebrospinal uid.63 Cross reactivity occurs with other agents of disseminated mycoses, such as Blastomyces species.66 Research on the use of antigen detection tests to diagnose canine and feline histoplasmosis is limited. Full validation of these tests for dogs and cats is pending. TREATMENT Although canine pulmonary histoplasmosis may be selflimiting and resolve without treatment,7 antifungal therapy is recommended because of the risk of dissemination (Table 2).10,36 In people, itraconazole is the rst-line treatment for mild to moderate pulmonary or disseminated histoplasmosis, and amphotericin B is the rst-line treatment for severe pulmonary or disseminated histoplasmosis.67 Itraconazole or amphotericin B is considered the rst-line treatment for histoplasmosis in dogs and cats.10 25 µm 4. A liver aspirate from a cat. Three dark-purple hepatocytes are seen among multiple macrophages, some of which contain yeast (arrows). Several yeast are noted free in the background (arrowheads) of erythrocytes and a small amount of finely granular protein (Diff-Quik, 60X). Itraconazole Even though itraconazole is reportedly the treatment of choice for histoplasmosis in dogs and cats,10,38 few reports of speci c studies of its ef cacy in these species exist. One report indicated good ef cacy in eight cats treated with itraconazole (5 mg/kg orally b.i.d.) for 60 to 130 days, with two cats relapsing and requiring additional therapy to achieve complete remission.38 Because of marked variability in the oral absorption of itraconazole, some cats may require twice-daily dosing at 10 mg/kg.68 Different formulations of itraconazole exist (Table 2); of these, the oral suspension has the greatest bioavailability.22,68,69 Use of the intravenous formulation of itraconazole may be considered in animals that cannot be treated with an oral formulation. However, little data exist on the use of intravenous itraconazole in dogs and cats.22,69 25 µm Fluconazole No studies evaluating uconazole therapy in dogs and cats with disseminated histoplasmosis exist. But since uconazole has increased penetration into the eye and central nervous system, it may theoretically be a better azole agent for patients that have neurologic or ocular involvement refractory to itraconazole.10 Results of an in vitro study showed that uconazole had a higher minimal inhibitory concentration than itraconazole for Histoplasma species.70 However, in 5. A lung aspirate from a cat. Multiple foamy activated macrophages are noted, including a single giant cell on the far left. One macrophage contains several yeast (arrow). Several yeast are noted in the background (arrowheads) of erythrocytes and a small amount of finely granular protein. Also note the morphologically normal respiratory epithelial cells with their tufts of apical cilia to the right of the micrometer (Diff-Quik, 60X). 256 May 2008 VETERINARY MEDICINE
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