A case of feline phaeohyphomycosis due to Fonsecaea pedrosoi

Hyphae, pseudohyphae, yeasts, spherules, spores, and more: A review on the morphology and pathology of fungal and oomycete infections in the skin of domestic animals

Fungi are among the most common infectious agents affecting the skin of animals. The skin can serve as a port of entry for fungal infections, which can eventually become disseminated. In some regions of the world, oomycetes, such as Pythium and Lagenidium, are also responsible for a significant number of severe cutaneous infections. Histologic evaluation of fungal morphology, including size, shape, septation, branching, and budding characteristics, combined with the distribution of inflammatory infiltrates within different skin layers can potentially identify etiologic agents, guiding selection of antifungals and additional diagnostics. Fungal infections of the skin surface are typically caused by Malassezia and rarely Candida, with opportunistic fungi also capable of colonizing the skin surface, especially when the barrier is broken. Folliculocentric infections, caused by dermatophytes, result in mild to severe inflammation and can occasionally penetrate deep into the skin. A wide range of fungi, including agents of hyalohyphomycosis, phaeohyphomycosis, and dimorphic fungal infections, as well as oomycetes, result in nodular cutaneous and subcutaneous lesions. With the occasional exception of dimorphic fungi, fungal speciation often requires cultures performed on fresh tissues. However, molecular techniques such as pan-fungal polymerase chain reaction on paraffin blocks is becoming an increasingly useful tool to distinguish between cutaneous fungal pathogens. This review focuses on describing the clinical and histologic features of the most common fungal and oomycete infections affecting the skin of animals, divided according to distribution patterns of lesions and fungal or oomycete morphology.

First report of phaeohyphomycosis caused by Phialophora americana in a domestic cat from Argentina

Case summary

A 10-year-old male neutered domestic shorthair cat from Quilmes (Province of Buenos Aires, Argentina) presented at the Infectious Diseases and Parasitology Unit with a hyperpigmented nodule of 5 cm diameter on the nasal plane with a small ulceration of more than 1 year’s evolution. A scaly and hyperpigmented alopecic lesion of 3 cm in diameter was found on the lower edge of the tail. The patient was under immunosuppressive therapy with corticosteroids for lymphoplasmacytic duodenitis. Samples of the lesion present on the nasal plane were taken under a surgical procedure. In the wet mount preparations, pigmented irregular hyphae were observed. They developed dark colonies when cultured on Sabouraud medium. On micromorphology, structures compatible with Phialophora species were identified. PCR and sequencing of ITS (ITS1-5.8S-ITS2) confirmed Phialophora americana as the etiologic agent. A therapeutic scheme that included a combination of itraconazole oral solution (1.5 mg/kg PO q12h) with terbinafine (30 mg/kg PO q24h) was indicated for a period of 10 months. The patient died of complications resulting from its underlying disease.

Relevance and novel information

As far as the authors are aware, this is the first study to report P americana as an etiologic agent of phaeohyphomycosis in cats. In this case study, the species was identified using molecular tests.

Opportunistic Fungal Infections in Small Animals

Opportunistic fungal infections have long been recognized as rare causes of disease in immunocompetent dogs and cats. Recently, the escalating use of multiagent immunosuppression protocols (especially those that include cyclosporine) has resulted in an increased number of patients with opportunistic fungal infection encountered by small animal practitioners and has altered the typical case phenotype. Based on histologic and cytologic features such as pigmentation, hyphal diameter, and distribution in tissue, these opportunistic mycoses can be placed into categories such as phaeohyphomycosis, hyalohyphomycosis, and eumycotic mycetoma. This review aims to summarize the clinical presentations, methods for diagnosis, treatment recommendations, and prognosis for both immunocompetent and immunosuppressed patients with opportunistic fungal infections. An example case description is included to illustrate the most common current clinical presentation.

Cerebral pyogranulomatous encephalitis caused by Cladophialophora bantiana in a 15-week-old domestic shorthair kitten

Case summary

A case of cerebral phaeohyphomycosis caused by Cladophialophora bantiana is described in a 15-week-old domestic shorthair kitten.

Relevance and novel information

Cerebral phaeohyphomycosis is a rare condition in cats caused by dematiaceous fungi. This report describes the clinical and histopathological findings in the youngest case documented in a feline, provides a brief review of aetiology, diagnosis, treatment and prognosis of cerebral phaeohyphomycosis and demonstrates the importance of molecular diagnostics in accurate mycotic species identification.

Rare opportunistic mycoses in cats: phaeohyphomycosis and hyalohyphomycosis

Overview:

Phaeohyphomycoses and hyalohyphomycoses are rare opportunistic infections acquired from the environment. More cases have been reported in recent years in humans and cats.

Disease signs:

Single or multiple nodules or ulcerated plaques (which may be pigmented) in the skin are the typical lesions. In some cases the infection disseminates or involves the central nervous system (CNS).

Diagnosis:

Diagnosis is based on fungal detection by cytology and/or histology. Culture provides definitive diagnosis and species identification.

Treatment:

Treatment involves surgical excision in cases of localised skin disease followed by systemic antifungal therapy, with itraconazole as the agent of first choice. Relapses after treatment are common. Itraconazole and other systemic antifungal agents have been used to treat systemic or neurological cases, but the response is unpredictable. The prognosis is guarded to poor in cats with multiple lesions and systemic or neurological involvement.

Zoonotic risk:

There is no zoonotic risk associated with contact with infected cats.

Phaeohyphomycoses, emerging opportunistic diseases in animals

Emerging fungal diseases due to black yeasts and relatives in domestic or wild animals and in invertebrates or cold- and warm-blooded vertebrates are continually being reported, either as novel pathogens or as familiar pathogens affecting new species of hosts. Different epidemiological situations can be distinguished, i.e., occurrence as single infections or as zoonoses, and infection may occur sporadically in otherwise healthy hosts. Such infections are found mostly in mammals but also in cold-blooded animals, are frequently subcutaneous or cerebral, and bear much similarity to human primary disorders. Infections of the nervous system are mostly fatal, and the source and route of infection are currently unknown. A third epidemiological situation corresponds to pseudoepidemics, i.e., infection of a large host population due to a common source. It is often observed and generally hypothesized that the susceptible animals are under stress, e.g., due to poor housing conditions of mammals or to a change of basins in the case of fishes. The descriptions in this article represent an overview of the more commonly reported and recurring black fungi and the corresponding diseases in different types of animals.

Invasive mould infections of the naso-orbital region of cats: a case involving Aspergillus fumigatus and an aetiological review

CASE AND CONTEXT: This report describes a cat diagnosed with sinonasal-orbital Aspergillus fumigatus infection using advanced imaging, histopathology and culture. Aetiology, clinical aspects and treatment of this rare and devastating infection are discussed with reference to a literature review of invasive mould (ie, filamentous fungal) infections involving tissues of the naso-orbital region of cats.

PRESENTATIONS

Invasive fungal infections can present with different localisations (nasal passages, sinuses, orbits, subcutaneous space, palate, etc) depending on the species involved and its means of introduction into the tissues. Localised subcutaneous lesions (swellings, ulcerations, masses, nodules, etc), without concomitant signs of nasal/orbital disease, generally result from traumatic injuries and subsequent inoculation of fungal spores into the subcutaneous space. In contrast, naso-ocular involvement and concurrent signs of nasal disease (nasal discharge, sneezing, masses protruding from the nostrils) generally result from inhalation of spores, with subsequent spread of infection into the nasal planum or penetration of overlying bone and invasion of the subcutaneous space. Aspergillus species typically show such an invasion mechanism and frequently affect orbital tissues. Dematiaceous fungi (ie, filamentous fungi with brown/black hyphae) are reported to cause solitary, less invasive, slowly developing lesions, probably as a result of traumatic injuries with inoculation of fungal propagules. Accordingly, the subcutaneous space is more frequently primarily involved.

TREATMENT AND OUTCOME

Whatever the mould species, reported treatment options include surgery and a series of antifungal drugs. The outcome is frequently poor, especially for Aspergillus infections, although various measures can be taken to maximise the chances of success, as discussed in this report.

Focal pulmonary granuloma caused by Cladophialophora bantiana in a domestic short haired cat

Following a 4-week history of coughing, a 12-year-old cat with a history of insulin-dependent diabetes mellitus was diagnosed with a pulmonary granuloma caused by Cladophialophora bantiana. Thoracic radiographs revealed consolidation of the right caudal lung lobe and cytology confirmed the presence of mycotic pneumonia. Results of clinical investigations showed no evidence of extra-pulmonary infection. A thoracotomy and lung lobe resection was performed. Histological examination of the mass revealed black pigmented fungal hyphae and pyogranulomatous inflammation. Cultures inoculated with portions of these tissues yielded a dark walled fungus consistent with an etiologic agent of phaeohyphomycosis and DNA sequencing confirmed the presence of Cladophialophora bantiana. The cat was treated with itraconazole for 4 weeks post-operatively and then with posaconazole for 7 months but was euthanized 13 months after initial diagnosis due to a hepatocellular carcinoma. On post-mortem examination there was no evidence of recurrent fungal infection. This is the first report of localized pulmonary C. bantiana infection in a cat.

Nodular granulomatous fungal skin diseases of cats in the United Kingdom: a retrospective review

IDEXX Laboratories database of cases submitted from the UK between March 2005 and February 2008 (36 months) was investigated for feline nodular granulomatous skin disease associated with fungal infection. Cytological and/or histological slides were reviewed and the diagnosis was based on the microscopic pattern of the inflammatory response and morphology of the causative organism. Aetiological diagnoses were hyalohyphomycosis (64 of 77 cases), phaeohyphomycosis (five of 77 cases) and dermatophytic pseudomycetoma (eight of 77 cases). All cases of hyalohyphomycosis were suspected to be alternariosis based on common features including anatomical distribution of lesions (48 of 64 cases involved the nostril and bridge of nose, face and ears), pattern of histological changes, morphology of the causative organism and results of fungal culture (Alternaria three of 16 and 'saprophyte' nine of 16 cases). Cases of phaeohyphomycosis were demographically and histologically similar to those of alternariosis, except the causative organisms were deeply pigmented brown and had a variety of morphologies that were different from Alternaria. Dermatophytic pseudomycetomas had a characteristic histological pattern including the presence of fungal microcolonies or grains within the tissue. These occurred most often on the trunk (five of eight cases) and four of eight cases were in Persian cats. These findings indicate that alternariosis is by far the most common nodular fungal skin disease of cats in the UK.

Fonsecaea pedrosoi skin infection in a dog

Fonsecaea pedrosoi is the most common fungal agent associated with human chromoblastomycosis. In the current study, a phaeohyphomycotic condition of the skin caused by Fonsecaea pedrosoi is described in a dog.

Biology and pathogenesis of Fonsecaea pedrosoi, the major etiologic agent of chromoblastomycosis

Fonsecaea pedrosoi is the principal etiologic agent of chromoblastomycosis, a fungal disease whose pathogenic events are poorly understood. Treatment of the disease presents poor effectiveness and serious side effects. The disease is epidemiologically important in several regions, which has stimulated studies focused on the biology and pathogenic potential of its major causative agent. In this review, we summarize the current knowledge on the biological aspects of F. pedrosoi, including cell differentiation and pathogenic mechanisms during the interaction of fungi with different hosts' elements.

Fatal systemic phaeohyphomycosis caused by Ochroconis gallopavum in a dog (Canis familaris)

A 5-year-old Shetland Sheepdog was presented with a history of weakness, ataxia, anemia, thrombocytopenia, and occasional seizures. The dog had been treated for 6 months with prednisone for inflammatory bowel disease. A positive titer for Ehrlichia canis was detected 6 months before referral. The initial physical examination revealed a weak, laterally recumbent dog with pale mucous membranes. Neurologic examination revealed multiple neurologic deficits. A complete blood cell count (CBC) revealed normochromic, normocytic, nonregenerative anemia; lymphopenia; thrombocytopenia; and neutrophilic and monocytic leukocytosis. Urinalysis revealed proteinuria, with a specific gravity of 1.045. The dog was unresponsive to treatment and died. At necropsy, there was severe serofibrinous peritonitis and pleuritis, with randomly scattered dark brown necrotic foci present in multiple organs, including liver, spleen, kidney, and pancreatic lymph node. Histologically, there were extensive regions of parenchymal necrosis surrounded by neutrophils admixed with epithelioid macrophages, lymphocytes, and pigmented fungal organisms. Numerous brown, 2 to 6 microm in diameter, septate, branching hyphae, subsequently identified as Ochroconis gallopavum (formerly Dactylaria constricta var. gallopava), were observed.

First cases of animal diseases published since 2000. 2. Cats

In this second article of a series of papers listing first case reports of animal diseases published since 2000, the following nine cases of cat diseases are discussed: Congenital spongiform change in the brain stem nuclei. Enterococcus hirae enteropathy. Focal cerebral angiomatosis. Glomus tumor. Intraocular extramedullary plasmacytoma. Lens epithelial neoplasias. Phaeohyphomycosis due to Fonsecaea pedrosoi. Pulmonary lymphomatoid granulomatosis. Systemic amyloidosis in a Devon rex. After a short introduction, the bibliographical data, the abstract of the author(s) and some additional information derived from the article are given. The article will be regularly updated adding overlooked as well as new first reports.

Antifungal agents of use in animal health--practical applications

The purpose of this paper is to provide an overview of antifungal agents currently in use in veterinary medicine. The practical applications and the therapeutic regimens that have proved successful in the treatment and prevention of fungal infections in dogs and cats, cattle and sheep, horse, pig, poultry and other birds, rodents, rabbits and fur animals are summarized.

Feline cutaneous phaeohyphomycosis due to Cladophyalophora bantiana

A case of feline cutaneous phaeohyphomycosis due to Cladophyalophora bantiana is described. The cat was presented with breathing difficulty and a swollen, ulcerated nodule on the dorsal nose and left nostril. Histological examination of the nodule revealed a cystic granulomatous dermatitis characterised by neutrophils, macrophages and giant cells. Pigmented, yeast-like fungus cells and hyphal elements were easily identified in haematoxylin-eosin stained tissue sections. Cladophyalophora bantiana was isolated from a tissue specimen. This organism, primarily known to cause cerebral infection in humans and cats, only rarely causes cutaneous infection. Despite anti-fungal chemotherapy two relapses occurred. The cat was feline immunodeficiency virus- and feline leukemia virus-negative and even if the owner was unaware of trauma, the hypothesis of wound contamination is the most likely.