Phaeohyphomycosis is a diverse group of fungal infections, caused by dematiaceous fungi whose morphologic characteristics in tissue include hyphae, yeast-like cells, or a combination of these. It can be associated with an array of melanistic filamentous fungi including Alternaria species, Exophiala jeanselmei, and Rhinocladiella mackenziei. The term "phaeohyphomycosis" was introduced to determine infections caused by dematiaceous (pigmented) filamentous fungi which contain melanin in their cell walls. Phaeohyphomycosis is an uncommon infection, but the number of cases reported has been increasing in recent years. Fungal melanin is thought to be a virulence factor. The outcome of antifungal treatment is poor, and mortality is almost 80%. Phaeohyphomycosis has been attributed to more than 100 species and 60 genera of fungi over the past several decades. The pathogens are considered opportunistic. Almost all cases of widely disseminated infection have occurred in immunosuppressed people.
Clinical signs of phaeohyphomycosis
Wildlife Phaeohyphomycosis is found throughout the animal kingdom. From molluscs to humans, different strains of this fungus affect animals differently, based on how severely the fungus has infected the animal. The clinical signs depend on the species of animal that is infected as well as the strain of fungus it is infected with. This disease is usually found more often in stressed animals after removal from their habitat.
Invertebrates Invertebrates, such as crabs and mollusks, show a variety of clinical signs. Crabs had increasingly weak motor control, especially in legs and claws, and were lethargic. They had poor balance and tetany, or muscle spasms, in the claws. Finally, they had tissue necrosis, which caused deterioration of the epidermis, connective tissue, heart, hepatopancreas, nervous system, and gills. In severe cases, there was congestion of hemal sinuses, two principal empty areas along the digestive tube and vessels. Mass amounts of yeast-like cells compressed nerve fibers and the gill lamellae were destroyed. Mollusks clinical signs vary from scattered spots of brownish discoloration on the mantle tissues to general deterioration of mussel condition. In severe cases, there were black-bodied mussels with a distinct odor and black yeast cells infected the connective tissues around the gonads and the digestive tract.
Cold-blooded vertebrates Cold-blooded vertebrates can exhibit an assortment of clinical signs. Amphibians may show signs of anorexia. Ulcers or nodules in the skin can be found, as well as swelling and lesions of internal organs, including the spleen, liver, and kidney. In extreme cases, neurological disorders and multifocal dermatitis (swelling caused by irritation of the fungus) can occur. Fish demonstrate signs of lethargy and disoriented swimming. Ulcerative lesions, multiple dark foci in the gills, and non-ulcerative dermal masses may be found. In critical cases, some fish show a variety of inflammatory responses including the formation of microabscesses. Lesions in the brain and kidneys may be present. These fish have abnormal swimming behavior, bulging eyes, and abdominal swelling.
Warm-blooded vertebrates From birds to equines, phaeohyphomycosis persists and has a massive range of clinical signs throughout differing species. Infected poultry and wild birds can develop neurological disorders and a loss of movement control. They may experience severe torticollis, which are severe muscle spasms that compromise the bird's ability to hold up its head. Birds can exhibit a loss of balance due to the rigidity of their legs. Cats can exhibit signs of breathing difficulty due to excessive swelling of the nose. Lesions may occur throughout the body, including the brain. Common lesions include ulcerated cutaneous nodules of the digits, pinnae, nasal planum, and nasal/paranasal tissues. In extreme cases dogs exhibit vision impairment and have deep infections in the nasal cavity, kidneys, and the cerebellum. In dogs, brain infections similar to infections found in humans may occur. Other clinical signs are lesions, abscesses, and severe inflammation throughout the dog's body. Ruminants and equines are affected the same way from phaeohyphomycosis. They can exhibit respiratory distress with constant coughing and a fever. They demonstrate signs of anorexia, lethargy, and hypothermia. There may be inflammation, hair loss, scaling, and damage to the cerebellum.
Humans Humans' clinical signs consist of swelling and eye infections. Nodules underneath the skin, abscesses or cysts may be present. and lesions can run throughout the body, including papules, plaques and granulomatous damage. In extreme cases there can be deep infections within the eyes, bones, heart and central nervous system.
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