https://www.cdc.gov/healthypets/index.html (keeping pets healthy keeps humans healthy)

Mycology is the study of fungi. Fungi are eucaryotes with a that has ergosterol as a key component rather than cholesterol. This is an importance difference since many antifungal agents are directed towards ergosterol. Fungi also have a rigid cell wall that contains chitin as well as hyphae which are branching, threadlike tubular filaments.

Most fungi are not pathogens but they can produce toxins and cause allergies (primarily ). For example, spoiled peanuts and other grains contain coumarin derivatives produced by Aspergillus flavus and cause liver damage. Claviceps purpura also infects grains and produces lysergic acid diethylamide, commonly known as “LSD”.

The phylum Ascomycota contains about 30k species and includes about 75% of the known fungi. Among the ascomycetes are important fungi such as bread yeasts. The ability of yeasts to fermetn carbohydrates, breaking down glucose to produce thanol and CO2, is exploited in the production of bread, beer, and wine. Penicillium chrysogenium produces penicillin.

Fungi can be detected by 1) microscopic examination with the use of fungal stains (ex.India ink) or with KOH which dissolves host tissue leaving alkali resistant fungi or by the unique morphology of fungi (e.g., hyphae), 2) culture (media that inhibits bacterial growth like Sabouraud’s agar), 3) DNA probes or 4) serology (detection of specific antibodies).

Superficial Mycoses 

Superficial mycoses live on dead skin and hair and do not elicit an immune response. Superficial mycoses include Tinea versicolr, Tinea nigra, Black and White piedra which grow on hair shafts.

cutaneous mycoses 

Cutaneous mycoses are caused by dermatophytes and infect keratinized skin, hair and nails. Cutaneous mycoses invoke an immune response. Diseases are very common and include ringworm or tinea (e.g., Tinea pedis).

subcutaneous mycoses 

Subcutaneous mycoses are lesions in deeper skin layers usually caused by a trauma such as a thorn. For example,  sporotrichosis (“Rose grower’s disease”) typically occurs when one is pricked by a thorn which has the Sporothrix schenckii fungus agent. Other subcutaneous infections are Chromoblastomycosis and Mycetoma.

Sporotrichosis: is an implantation mycosis caused by fungi in the genus Sporothrix. It affects humans and other mammals. Although cat-transmitted sporotrichosis casued by the highly transmissible Sporothrix brasiliensis species is an increasing concern in Latin America, S. Brasiliensis has not been detect in the US and cat-transmitted Sporothrix schenckii is rarely reproted. However recently a clustor of sporotrichosis cases involving 2 domestic cats and zoonotic transmission between one of the affected cats and a veterminary technician was reproted. (Toda “Sporotrichosis Cluster in domestic cats and veterinary technician, Kansas, USA, 2022” Emergingin Infectious Diseases, May 2024).

Early diagnosis of sporotrichosis and early treatment initiation with appropirate antifungal drugs can improve outcomes and help prevent transmission to other cats or humans. Cytology and culture should be considered for wounds or lesions taht fail to respond to antibiotics. Itroconazole should be given to cats with food to improve adsorption, and potassium iodide in combination with itraconazole can improve treatment of efficacy in cats with multiple or extensive lesions or in treatment refractory cases. (Toda “Sporotrichosis Cluster in domestic cats and veterinary technician, Kansas, USA, 2022” Emergingin Infectious Diseases, May 2024).

To reduce zoonotic transmission risk, veterinary professionals should wear examination gloves when handling cats with suspected sporotrichosis and take prevautions to avoid scratches or bits. Wounds form scratches or bits should be washed promptly with soap and water. (Toda “Sporotrichosis Cluster in domestic cats and veterinary technician, Kansas, USA, 2022” Emergingin Infectious Diseases, May 2024).

systemic mycoses 

Systemic mycoses are inheritently infectious and include the following:

Histoplasmosis otherwise known as “Darling’s” “cave” or “spelunker’s” disease. Histoplasmosis occurs in the midwest. Infection is due to inhalation of conidia or hyphal fragments which are phagocytized by pulmonary macrophages. It is usually found on bird dropping and is a dimorphic fungus in that it can exist in the yeast (e.g., macophages)  or mold (e.g., soil) form. Treatment may include itraconazole and/or amphotericin B.

Blastomycosis otherwise known as “Gilchrist’s” or “Chicago” disease is endemic in Ohio and the Mississippi Valley.

Treatment can again be amphotericin B.

Coccidioidomycosis otherwise known as “Posada-Wernicke” or “San Joaquin Valley vever” is endemic in California and Texas.

Treatment can again include amphotericin B.

opportunistic mycoses 

Opportunistic mycoses are pathogenic in immunocompetent individuals and include

Aspergillosis such as A. fumigatus, A. flavus, A. niger are ubiquitous in damp basements and vegetation. It can cause blockage of airways from fungal masses.

Treatment can include surgery, amphotericin B or itraconazole.

Cryptococcosis neoformans

Candidiasis is a dimorphic fungus with yeast on mucosal surfaces. It is actually part of one’s normal flora in skin, mouth and intestines and stays as yeast but it forms hyphae when invasive. When the normal balance of microbiota is disrupted, the yeast proflierates and causes inflaamtion.

Treatment includes cessation of antibiotic and can also include itraconzaole.