Histoplasmosis is a chronic, noncontagious, disseminated, granulomatous disease caused by the dimorphic fungus Histoplasma capsulatum var capsulatum. This fungus is commonly found in soil that contains bird and bat feces. Histoplasmosis can affect both humans and animals, and in this article, we will focus on the treatment of histoplasmosis in animals.
When an animal inhales environmental microconidia containing Histoplasma capsulatum, the initial infection is established in the lungs and thoracic lymph nodes. The clinical signs of histoplasmosis may vary and are usually nonspecific. However, common symptoms include weight loss, fever, pale mucous membranes, and peripheral lymphadenopathy.
In cats, tachypnea (rapid breathing) and cutaneous signs are often present. Dogs, on the other hand, may experience hepatomegaly (enlarged liver), ascites (abnormal accumulation of fluid in the abdomen), and diarrhea. Both dogs and cats may also develop ocular involvement such as optic neuritis, chorioretinitis, or retinal detachment. In some cases, histoplasma meningitis may occur, and skin lesions may develop.
To diagnose histoplasmosis in animals, fine-needle aspiration and exfoliative cytology can often provide a definitive diagnosis. Histoplasma organisms are usually numerous in affected tissues. Additionally, they may be detected within monocytes or neutrophils on routine blood smears in cases of disseminated disease. In cats, cytology of bone marrow can be diagnostic. If cytology is inconclusive, a tissue biopsy may be necessary.
Histoplasma organisms are difficult to detect with routine stains but can be visualized well with fungal-specific stains. The yeast forms in phagocytes and giant cells are round to ovoid structures with a thin cell wall and a clear zone between the cell wall and cellular cytoplasm. Narrow-based budding may also be observed.
Culturing Histoplasma capsulatum from tissue specimens, fine-needle aspirates, and body fluids is possible but requires caution due to the hazardous nature of the fungus. Antigen testing using a quantitative antigen ELISA can be performed on urine, serum, and cerebrospinal fluid (CSF), with urine being the most sensitive substrate. However, cross-reactivity can occur with other fungal antigens such as Blastomyces.
The treatment of choice for disseminated histoplasmosis in dogs and cats is itraconazole. The recommended dosage is 10 mg/kg every 24 hours. Fluconazole is also effective for treatment. In early or mild cases of histoplasmosis in dogs, ketoconazole at a dosage of 10-15 mg/kg every 12 hours for 4-6 months may be effective, although resistance has been documented.
For severe cases, concurrent treatment with amphotericin B or amphotericin B lipid complex is suggested. The duration of treatment depends on the severity of the disease. A minimum of 6 months is recommended, but many patients require more than 12 months of treatment. The decision to discontinue treatment should be based on the resolution of clinical signs and urine antigen titers. It is important to note that relapses can occur in 10%-40% of patients.
Histoplasmosis is a serious fungal disease that can affect animals. Prompt diagnosis and appropriate treatment are crucial for the well-being of affected animals. If you suspect your pet may have histoplasmosis or require assistance with any bird-related cleaning services, please contact Bird Poop Cleaning at [hello@khunclean.com] or call us at [082-797-3702]. Our team of experts is here to help.
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