Veterinary Medicine - May 2008 - (Page 259) not recommended in treating histoplasmosis. However, airway obstruction from enlarged hilar lymph nodes and in ammation associated with proliferation of the organism in the lungs can be life-threatening.10 In a study of dogs with enlarged hilar lymph nodes secondary to chronic pulmonary histoplasmosis, corticosteroid administration (prednisone 2 mg/kg orally every 12 to 24 hours) resulted in the resolution of the clinical signs of airway obstruction in less than one week, compared with 8.8 weeks in dogs treated with antifungal therapy.17 Only consider using corticosteroids if there is marked respiratory compromise and if no organisms are found on cytologic or histologic evaluation. Additional supportive therapy for pulmonary histoplasmosis may include oxygen supplementation and antibiotics, if clinically indicated.11 apply for animals exhibiting signs of cutaneous vasculitis.81 Response to therapy should be evaluated through the resolution of clinical signs, hematologic and biochemical abnormalities, and radiographic lesions.10 Treatment is continued for a minimum of one month past resolution of clinical signs, and animals should be reevaluated for evidence of relapse three and six months after therapy is discontinued.11 PROGNOSIS The prognosis depends primarily on the extent and severity of infection. Pulmonary histoplasmosis may resolve without speci c antifungal therapy,82 and dogs and cats with pulmonary histoplasmosis can have a good prognosis. The prognosis for disseminated histoplasmosis depends on the degree of dissemination and severity of clinical signs.10,11 While central nervous system involvement often carries an unfavorable outcome,33,34 recovery of neurologic function is possible.45 With ocular involvement, the prognosis for return of vision is guarded to poor.37 One recent report of feline ocular histoplasmosis documented return of vision with complete resolution of retinal hemorrhages six months after the initiation of systemic itraconazole therapy in a cat.39 TREATMENT DURATION AND MONITORING While the duration of therapy is variable, most patients treated with antifungal drugs will receive these medications for a minimum of four to six months or two months after resolution of all clinical signs.10 Patients should be rechecked at monthly intervals. In addition to physical and ocular examinations, a serum chemistry pro le is recommended to monitor hepatic enzyme activity while an animal is receiving azole antifungal therapy.11 In a study of 112 dogs treated with itraconazole, anorexia was the most common adverse effect and was usually associated with an increase in ALT activity. The anorexia resolved within three or four days after the medication was stopped, and therapy was reinstituted one week after discontinuation.79 In dogs, if the serum ALT activity is > 250 IU/L, consider discontinuing itraconazole therapy.80 In dogs and cats with anorexia and increased ALT activity, treatment can be resumed at half the original dose once the anorexia resolves or the hepatic enzyme activity returns to reference values.22,81 Similar recommendations PREVENTION Vaccination against histoplasmosis is not available in cats and dogs, so the recommended method of protection is preventing exposure to potentially Histoplasma species-laden areas, such as chicken coops, bird and bat roosts, and construction and excavation sites.4,10 SUMMARY Histoplasma capsulatum is a saprophytic, dimorphic fungus that affects people and animals. The primary route of transmission is by inhaling conidia from the soil. It is thought that most infections are self-limiting, but pulmonary or disseminated disease may occur. Clinical signs in cats are often chronic VETERINARY MEDICINE May 2008 259 http://www.idexx.com/snapfelinetriple http://www.idexx.com/snapfelinetriple
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