FungaL Diseases
Ringworm and other fungal infections usually occur when nutrition or environmental conditions are inadequate. Crusting, alopecic skin disease should not be assumed to be of fungal origin without laboratory confirmation.
Ringworm
EtioLogy
A variety of dermatophytes have been cultured from ringworm in goats. These include Microsporum canis and Microsporum gypseum; Trichophyton mentagrophytes, Trichophyton schoenleinii, and Trichophyton verrucosum; and Epidermophyton floccosum (Philpot et al. 1984; Scott 1988; Eljack et al. 2011).
CLinicaL Signs and Diagnosis
Lesions in goats consist of alopecia, scaling, erythema, and crusts. They typically involve the face, external ears, neck, or limbs, and may be annular in shape (Scott 2018). Pruritus is not usual, but has been reported (Chineme et al. 1981). Microscopic examination of hairs and keratin from the periphery of an active lesion (as described above) may reveal ectothrix invasion of hair shafts. Species identification requires culture and examination of both colony and microscopic morphology.
Treatment and Prevention
Young animals (Pandey and Mahin 1980) or those living in a dark, damp, dirty environment, or those with debilitating nutritional or infectious diseases, are most at risk for developing ringworm. Management changes, then, may be required to control an outbreak in goats. Most cases of dermatophytosis in large animals regress spontaneously in one to four months. Thus, although oral griseofulvin has been reported to be effective in treating ringworm in goats at 25 mg/kg/day for three weeks (Chineme et al. 1981), this expensive therapy is usually not justified (Scott 1988).
Topical treatment does reduce contamination of the environment and the risk of spread to other animals or man. People handling infected goats should take precautions to avoid contracting the infection themselves.
Lime sulfur (2-5%), iodophors, and 0.5% sodium hypochlorite as total body sprays daily for five days and then weekly are recommended for ringworm (Scott 1988). Benzalkonium chloride is also recommended as an antifungal. Captan (3%) is effective (Scott 1988), but not approved in the United States for food-producing animals. Topical iodine ointments or products for athlete's foot (tinea pedis) can be used on small lesions. All in-contact animals should also be treated, and the environment disinfected with 0.5% sodium hypochlorite in hot water if possible. Pens that have previously housed young cattle with ringworm should be thoroughly disinfected before goats are introduced.Yeast Infections
Budding yeasts are occasionally present in large numbers in skin impression smears or biopsy samples taken from goats with alopecia, scaling, and crusting (Scott 1988). In most instances they probably represent secondary opportunists (Reuter et al. 1987). The hair coat is often greasy, but neither painful nor pruritic (Scott 2018), although mild pruritus has been reported by others (Eguchi-Coe et al. 2011). The dermatitis can be either localized or generalized (Eguchi-Coe et al. 2011). A Malassezia (Pityrosporum) species was suspected in milking goats with annular lesion on the teats and udder, based on PAS-positive organisms seen in the epidermis (Bliss 1984). A Malassezia species, possibly M. pachyder- matis, was isolated from an adult goat with chronic greasy, seborrheic lesions over the trunk but sparing the extremities (Pin 2004). The animal responded rapidly to weekly chlorhexidine-containing shampoo and topical enilcona- zole. In a third reported case, Malassezia slooffiae in hyphal and yeast forms was identified in the skin of an adult Pygmy goat with a one-month history of weight loss and extensive alopecia and crusting of the body and limbs (Uzal et al. 2007). Goats with yeast infections should be evaluated for chronic wasting diseases, with special attention given to possible nutritional deficiencies (e.g., protein, trace minerals).
Miscellaneous Fungal Infections
Peyronellaea glomerata, ordinarily a saprophyte on decaying vegetation, has been isolated from hyperkeratotic ear lesions on goats (Dawson and Lepper 1970). Brown septate hyphae were abundant in the stratum corneum in skin biopsies.
Several fungal species can produce mycetomas (granulomatous subcutaneous lesions with draining sinuses and granular fungal elements) in goats (Gumaa et al. 1978; Gumaa and Abu-Samra 1981). Proliferation of the periosteum of underlying bone may be marked. Pythium insidio- sum has been reported to produce ulcerative skin lesions in a goat in Brazil (do Carmo et al. 2015, 2021). Zoospores in water are thought to penetrate hair follicles or damaged skin. Diagnosis will be by histology (with fungal hyphae staining with Grocott's methenamine silver stain), immunohistochemistry, culture, or molecular-based methods.
Cryptococcus neoformans, a rare cause of pneumonia and mastitis in goats, has also caused ulcerated granulomas in the skin of the head of one goat and in the nasal passage of another goat in Australia (Chapman et al. 1990). The diagnosis was made by demonstrating the oval or budding encapsulated organisms in smears, histopathology samples, or culture. Cryptococcus gattii was diagnosed as the cause of granulomas in the non-healing incision from a Cesarean section (Villarroel and Maggiulli 2012). The goat was treated with surgical debridement and six months of oral fluconazole at 5 mg/kg per day. Although no information was available on bioavailability of the drug from the rumen, clinical response was favorable.