Phaeohyphomycosis

Phaeohyphomycosis is a heterogeneous group of mycotic infections caused by dematiaceous fungi whose morphologic characteristics in tissue include hyphae, yeast-like cells, or a combination of these.:324 It can be associated an array of darkly-pigmented hyphomycetes including Alternaria species, Exophiala jeanselmei, and Rhinocladiella mackenziei. Phaeohyphomycosis is a heterogeneous group of mycotic infections caused by dematiaceous fungi whose morphologic characteristics in tissue include hyphae, yeast-like cells, or a combination of these.:324 It can be associated an array of darkly-pigmented hyphomycetes including Alternaria species, Exophiala jeanselmei, and Rhinocladiella mackenziei. The term “phaeohyphomycosis” was introduced to determine infections caused by dematiaceous or pigmented filamentous fungi which contain melanin in their cell walls. Phaeohyphomycosis is an uncommon infection, however the number of case reported has been increasing in recent years. The presence of melanin in cell walls may be a virulence factor for the pathogens caused by the fungi. 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 patients. Phaeohyphomycosis is found throughout the animal kingdom. From mollusks 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, 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 exhibited an assortment of clinical signs. Amphibians showed signs of anorexia. Ulcers or nodules in the skin were 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) occurred. Fish demonstrated signs of lethargy and disoriented swimming. There were ulcerative lesions, multiple dark foci in the gills, and non-ulcerative dermal masses found. In critical cases, some fish showed a variety of inflammatory responses including the formation of microabscesses. Lesions in the brain and kidneys were also found. These fish had abnormal swimming behavior, bulging eyes, and abdominal swelling.