Fungal infections
From Felipedia
Funguses commonly cause superficial skin diseases in cats but are responsible for severe and often fatal systemic infections. The most common and least pathogenic fungus which affects cats is Microsporum canis, causing Ringworm.
Other fungi are cultured included Aspergillus spp, Penicillium spp, Cladosporium spp, Scopulariopsis spp and lipophilic yeasts of the genus Malassezia spp.
Pathology
Exposure to or contact with a dermatophyte does not necessarily result in an infection. Infection may not result in clinical signs. Dermatophytes grow in the keratinized layers of hair, nail and skin. They do not thrive in living tissue or persist in the presence of severe inflammation. The incubation period is 1-4 weeks. An infected animal which is not showing signs may remain in this inapparant carrier state for a prolonged period of time. Some may never become symptomatic. Corticosteroids can modulate inflammation and prolong the infection.
Cats infected with FIV or FeLV may have a greater diversity of cutaneous and mucosal mycoflora than noninfected cats. However, infected cats may be no more likely than noninfected cats to expose humans to zoonotic fungi such as Cryptococcus spp and Microsporum spp. A greater diversity of fungal genera was isolated from retrovirus-infected cats, and Malassezia spp were more commonly recovered from these cats, compared with noninfected cats.
Clinical signs
Signs may range from an inapparent carrier state to alopecia which may be patchy or circular. The classic sign of circular alopecia is more common in cats but often misinterpreted in dogs. Scales, erythema, hyperpigmentation, and pruritus are variable. Paronychitis, granulomatous lesions, or kerions may also be seen. In cats, dermatophytosis should be considered as a differential diagnosis for miliary dermatitis and almost any other dermatitis.
| Skin | Systemic |
| Microsporum canis (skin) | Cryptococcus spp |
| Microsporum gypseum (skin) | Coccidioidomycosis (Coccioides immitis) |
| Trichophyton mentagrophytes (skin) | Cytauxzoon felis |
| Trichophyton rubrum (nasal cavity) | Aspergillosis (Neosartorya spp, Aspergillus flavus, A. fumigatus) (naso-orbital abscesses) |
| Malassezia spp (otitis externa / otitis media) | Histoplasma spp (Histoplasma capsulatum) |
| Trichosporon spp (nasal cavity) | Phaeohyphomycosis - opportunistic dematiaceous fungi |
| Prototheca spp (algae in nasal cavity) | Penicillium spp (naso-orbital abscesses) |
| Aphanoascus fulvescens (commensal) | Sporotrichosis (Sporothrix schenckii) |
| Chrysosporium parvum (keratinolytic) | Rhinosporidium spp (cause tumour-like growths resembling nasopharyngeal polyps) |
| Candida spp | Blastomyces dermatitidis |
| Scopulariopsis spp | |
| Mucor amphibiorum | |
| Pythium spp - naso-orbital abscesses |
References
1. August, JR (2006) Consultations in Feline Internal Medicine, Vol 5. Elsevier Saunders
