Infection of the subcutis of the nose in a cat caused by Mucor species: successful treatment using posaconazole

Invasive Fungal Infections and Oomycoses in Cats: 1. Diagnostic approach

CLINICAL RELEVANCE

In contrast to superficial fungal infections, such as dermatophytosis, invasive fungal infections (IFIs) are characterised by penetration of tissues by fungal elements. Disease can spread locally within a region or can disseminate haematogenously or via the lymphatics. The environment is the most common reservoir of infection. Since fungal spores are airborne, indoor cats are also susceptible to IFIs. Some environmental fungi are ubiquitous and present globally, while others are endemic or hyperendemic within specific geographic regions. Zoonotic pathogens include Microsporum canis, Sporothrix schenckii and Sporothrix brasiliensis.

AIM

In the first of a two-part article series, the approach to the investigation of feline IFIs and oomycoses is reviewed. As well as tips for diagnosis, and information on the ecological niche and distribution of fungal pathogens, the review covers clinical presentation of the most common IFIs, including cryptococcosis, histoplasmosis, blastomycosis, coccidioidomycosis, sporotrichosis, phaeohyphomycosis, aspergillosis and dermatophytic pseudomycetoma, as well as the oomycoses pythiosis, lagenidiosis and paralagenidiosis. In Part 2, the spectrum of activity, mechanisms of action, pharmacokinetic and pharmacodynamic properties and adverse effects of antifungal drugs are reviewed, and the treatment and prognosis for specific IFIs and oomycoses are discussed.

EVIDENCE BASE

The review draws on published evidence and the authors' combined expertise in feline medicine, mycology, dermatology, clinical pathology and anatomical pathology.

Invasive fungal infections and oomycoses in cats 2. Antifungal therapy

CLINICAL RELEVANCE

Invasive fungal infections (IFIs) and oomycoses (hereafter termed invasive fungal-like infections [IFLIs]) are characterised by penetration of tissues by fungal elements. The environment is the most common reservoir of infection. IFIs and IFLIs can be frustrating to treat because long treatment times are usually required and, even after attaining clinical cure, there may be a risk of relapse. Owner compliance with medication administration and recheck examinations can also decline over time. In addition, some antifungal drugs are expensive, have variable interpatient pharmacokinetic properties, can only be administered parenterally and/or have common adverse effects (AEs). Despite these limitations, treatment can be very rewarding, especially when an otherwise progressive and fatal disease is cured.

AIM

In the second of a two-part article series, the spectrum of activity, mechanisms of action, pharmacokinetic and pharmacodynamic properties, and AEs of antifungal drugs are reviewed, and the treatment and prognosis of specific IFIs/IFLIs - dermatophytic pseudomycetoma, cryptococcosis, sino-orbital aspergillosis, coccidioidomycosis, histoplasmosis, sporotrichosis, phaeohyphomycosis, mucormycosis and oomycosis - are discussed. Part 1 reviewed the diagnostic approach to IFIs and IFLIs.

EVIDENCE BASE

Information on antifungal drugs is drawn from pharmacokinetic studies in cats. Where such studies have not been performed, data from 'preclinical' animals (non-human studies) and human studies are reviewed. The review also draws on the wider published evidence and the authors' combined expertise in feline medicine, mycology, dermatology, clinical pathology and anatomical pathology.

ABBREVIATIONS FOR ANTIFUNGAL DRUGS

AMB (amphotericin B); FC (flucytosine); FCZ (fluconazole); ISA (isavuconazole); ITZ (itraconazole); KCZ (ketoconazole); PCZ (posaconazole); TRB (terbinafine); VCZ (voriconazole).

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.

A case of feline gastrointestinal eosinophilic sclerosing fibroplasia associated with fungal colonisation: endoscopic features, treatment and follow-up

Case summary

A 5-year-old castrated male domestic shorthair cat presented with a 3-month history of weight loss, chronic diarrhoea and vomiting. Examination revealed a large proximal duodenal lesion eventually diagnosed as feline gastrointestinal eosinophilic sclerosing fibroplasia (FGESF) associated with fungal filaments. Histological examination was performed following endoscopic biopsy. Direct examination and mycological culture of the duodenal biopsies revealed the presence of a siphomycetous fungus, which was further identified as Rhizopus microsporus. Treatment with prednisolone and ciclosporin for 3 months led to complete resolution of the clinical signs and marked improvement of the endoscopic lesions. Specific fungal treatment with amphotericin B was poorly tolerated.

Relevance and novel information

To the best of our knowledge, this is the first report of the characterisation of a siphomycetous fungus associated with FGESF lesions, and the first endoscopic description and diagnosis of FGESF without surgical biopsies. We hypothesise that the presence of R microsporus occurred because of disrupted mucosal integrity.

Cutaneous and Pulmonary Mucormycosis in Rag1- and Il2rg-deficient Rats

Immunodeficient rats are valuable in transplantation studies, but are vulnerable to infection from opportunistic organisms such as fungi. Immunodeficient Rag1- and Il2rg-deficient (RRG) rats housed at our institution presented with dark, proliferative, keratinized dermal growths. Histologic and PCR results indicated that the predominant organism associated with these lesions was fungus from the family Mucoraceae, mostly of the genus Rhizopus. The Mucoraceae family of fungi are environmental saprophytes and are often found in rodent bedding. These fungi can cause invasive opportunistic infections in immunosuppressed humans and animals. We discuss husbandry practices for immunosuppressed rodents with a focus on controlling fungal contaminants.

Novel treatment using topical malachite green for nasal phaeohyphomycosis caused by a new Cladophialophora species in a cat

CASE SUMMARY

A 1.5-year-old castrated male domestic shorthair cat presented with a 2 month history of progressive nasal swelling and hyporexia. Minimal improvement prior to referral was achieved with a course of antibiotics and glucocorticoids. Cytology of an ulcerative lesion on the dorsal aspect of the nose was consistent with a diagnosis of phaeohyphomycosis. The cat achieved static disease for 6 weeks following initiation of itraconazole but developed epistaxis at 9 weeks. CT of the head demonstrated nasal and frontal sinus involvement. Nasal biopsy and culture identified infection with a Cladophialophora species not previously reported to cause disease. Initial response to a combination of itraconazole and terbinafine was noted, but owing to severe thrombocytopenia this combination was discontinued. Voriconazole was used but discontinued because of adverse side effects. Posaconazole treatment was offered throughout the clinical course but rejected owing to financial constraints and an uncertain response to medical therapy. Rhinotomy with debulking of diseased tissue and topical malachite green treatment was performed. Following the procedure itraconazole was continued and the cat has had no recurrence for over 1 year.

RELEVANCE AND NOVEL INFORMATION

Infections by Cladophialophora species have been reported in veterinary species, including cats. The specific fungal organism isolated from this cat has not been previously reported to cause disease in humans or animals and has only been described in the mangroves of Brazil. Furthermore, this is the first report to describe the use of topical malachite green as a treatment for refractory phaeohyphomycosis.

Treatment of refractory sino-nasal aspergillosis with posaconazole and terbinafine in 10 dogs

OBJECTIVES

To determine the safety and efficacy of posaconazole and terbinafine for the treatment of naturally occurring sino-nasal aspergillosis in dogs refractory to conventional topical and systemic treatment.

MATERIALS AND METHODS

Ten client-owned dogs with sino-nasal aspergillosis and not responsive to conventional treatments were prospectively enrolled to receive a dose of 5 mg/kg posaconazole orally every 12 hours for six months. All dogs were concurrently treated with doses of 30 mg/kg terbinafine orally every 12 hours and 5 mg/kg doxycycline orally every 12 hours for 6 to 18 months.

RESULTS

All 10 enrolled dogs completed the study. The treatment response was defined as complete clinical remission (n=7) or partial clinical remission (n=3). Two dogs relapsed after cessation of combination therapy. All dogs lived more than one year after starting combination therapy and eight dogs are alive at the time of writing. No clinically relevant adverse reactions or increases in hepatic enzyme activity occurred during the combination therapy.

CLINICAL SIGNIFICANCE

The results of this study suggest that this combination therapy appears safe and well-tolerated for the treatment of refractory sino-nasal aspergillosis in dogs. Long-term survival is possible with prolonged treatment, but relapse is possible. Larger prospective studies are warranted to further evaluate these preliminary findings.

Posaconazole Pharmacokinetics in Healthy Cats after Oral and Intravenous Administration

BACKGROUND

Posaconazole is the most active available azole antifungal drug, but absorption and pharmacokinetics are not available to guide dosing regimens in cats.

OBJECTIVE

To determine the pharmacokinetics of posaconazole in cats given an IV solution and PO suspension.

ANIMALS

Six healthy, adult research cats.

METHODS

After a 12-hour fast, each cat received 15 mg/kg of posaconazole PO suspension with food. Four cats also received 3 mg/kg IV posaconazole after a 7-day washout period. Plasma was collected at predetermined intervals for analysis using high-pressure liquid chromatography (HPLC). Concentration data were analyzed using a 2-compartment pharmacokinetic analysis for IV administration data and a 1-compartment analysis with first-order input for PO administration data using Phoenix® software.

RESULTS

After IV dosing, volume of distribution (VSS ) was 1.9 (0.3) L/kg (mean, standard deviation), terminal half-life (T½ ) was 57.7 (28.4) hours, and clearance was 28.1 (17.3) mL/kg/h. After PO dosing, peak concentration (CMAX ) was 1.2 (0.5) μg/mL and T½ was 38.1 (15.0) hours. Bioavailability of PO suspension was 15.9% (8.6). No adverse effects were observed with either route of administration.

CONCLUSION AND CLINICAL IMPORTANCE

Despite low PO absorption, these data allow for simulation of PO dosage regimens that could be explored in clinical studies. Two regimens can be considered to maintain targeted trough concentrations of 0.5-0.7 μg/mL as extrapolated from studies in humans: (1) 30 mg/kg PO loading dose followed by 15 mg/kg q48h, or (2) 15 mg/kg PO loading dose followed by 7.5 mg/kg q24h.

Penicillium species-induced granuloma in a cat resulting in chronic lower urinary tract disease

A 5-year-old, female neutered Persian cat was admitted to the Small Animal Hospital (Chulalongkorn University, Bangkok, Thailand) with clinical signs of dysuria, haematuria and partial urethral obstruction that had manifested over several months. The animal also had hyperkalaemia and severe azotaemia at the time of presentation. Urinalysis showed haematuria, pyuria and the presence of several transitional cells. In addition, ultrasonography demonstrated an extraluminal mass between the neck of urinary bladder and the colon. Fine-needle aspiration of the mass revealed a fungal form with branching and septate hyphae. Consequently, itraconazole treatment was prescribed and clinical signs of improvement were seen after 7 days. However, 1 month later, the cat died of acute anaemia. Necropsy revealed the presence of extraluminal multifocal fungal granuloma at the neck of the urinary bladder, and contracted kidneys. Histopathological analysis of the fungal granuloma was found to be composed of branching, septate hyphal fungi together with inflammatory cells. Subsequent fungal culture and identification revealed this to be a species of Penicillium.

Duodenal perforation caused by Rhizomucor species in a cat

CLINICAL SUMMARY: A 7-month-old female Persian cat presented with gastrointestinal (GI) necrosis and perforation caused by Rhizomucor species. Unfortunately, the cat died of bacterial peritonitis and sepsis before a definitive diagnosis, based on histopathology and fungal culture, was achieved.

PRACTICAL RELEVANCE

This appears to be the first reported case of GI disease caused by Rhizomucor species in a cat. Mucorales infections typically cause acute and rapidly progressive disease. As illustrated by this case, clinicians should be alert to the potentially fatal consequences of an opportunistic Rhizomucor species infection in their feline patients.

Feline cryptococcosis: impact of current research on clinical management

DISEASE SUMMARY: Cryptococcosis, principally caused by Cryptococcus neoformans and Cryptococcus gattii, is the most common systemic mycosis of cats worldwide. Cats may be infected following inhalation of spores from the environment, with the nasal cavity suspected as being the initial site of colonization and subsequent infection. Other sites of infection in cats are the skin, lungs, lymph nodes, central nervous system (CNS), eyes and, occasionally, periarticular connective tissue. Cryptococcosis can be diagnosed using serology (antigen testing), cytologic examination of smears, histopathology or culture. Treatment of localized disease is generally successful using azole antifungal drugs; however, cats with CNS involvement or disseminated disease require additional treatment with amphotericin B, with or without flucytosine. The prognosis is variable, depending on host and pathogen factors. Some cats require long-term (>1 year) treatment or indefinite therapy.

PATIENT GROUP

Cats of any breed, gender and age may be affected. Retroviral status does not appear to be a risk factor for developing cryptococcosis and indoor cats are not protected from disease.

GLOBAL IMPORTANCE

Feline cryptococcosis occurs worldwide, but is most frequently reported in Australia, western Canada and the western United States. Species and molecular type vary in different geographical regions and may affect clinical presentation and antifungal susceptibility patterns.

CLINICAL CHALLENGES

Serologic tests that detect cryptococcal antigen in serum are sensitive and specific, but false negatives can occur in cats with localized disease. Long-term drug therapy can be expensive and has the potential for toxicity. The extent to which the pathogenicity and antifungal susceptibility is affected by molecular type is currently under study.

EVIDENCE BASE

This review draws on recent literature relating to epidemiology, CNS involvement and advanced diagnostic imaging to update clinicians regarding research findings relevant to clinical practice.

Subcutaneous infection of a cat by Colletotrichum species

A 13-year-old, domestic shorthair cat was presented for evaluation of a right tarsal mass. Physical examination revealed a 5 cm × 5 cm × 5 cm, soft, fluctuant, subcutaneous tarsal mass. Thoracic radiographs revealed several discrete lung parenchymal lesions. Abdominal ultrasound revealed abnormal architecture to both kidneys. Fungal culture and sensitivity from the subcutaneous mass revealed a uniform growth of Colletotrichum species that was susceptible to itraconazole. Colletotrichum species infection was confirmed in the subcutis and suspected to be disseminated. Colletotrichum species fungal infections in cats have not been previously documented.

Localised microsphaeropsis arundinis infection of the subcutis of a cat

CLINICAL PRESENTATION AND DIAGNOSIS: An 11-year-old spayed domestic crossbred cat was presented for two focal lesions affecting the subcutis that developed 3 weeks after a cat fight. Lesions consisted of swelling of the subcutaneous tissues over the bridge of the nose and a focal swelling of the dewclaw pad of the left thoracic limb. Both lesions were attributable to localised infections with the unusual fungal pathogen Microsphaeropsis arundinis, based on direct microscopy of smear cytology, histology, fungal culture, internal transcribed spacer-polymerase chain reaction (ITS-PCR) and sequence analysis of formalin-fixed tissue and colonial material from primary culture.

TREATMENT

The dewclaw pad lesion resolved following cytoreductive surgery and a course of itraconazole (50 mg once daily). The nasal bridge lesion was treated in a similar fashion, except that a range of different antifungal agents (itraconazole, fluconazole, posaconazole) were used, administered sequentially. Despite this, the infection recurred on three subsequent occasions, and the cat has been prescribed indefinite azole therapy.

PRACTICAL RELEVANCE

This report of a refractory localised infection of the subcutis in an apparently immune-competent cat illustrates the value of using a mycology reference laboratory, and PCR and sequence analysis for organism identification, and the therapeutic potential of new antifungal agents such as posaconazole.

Phaeohyphomycotic osteomyelitis in the femur of a cat

A 4-month-old castrated male domestic shorthair cat was presented for a right hind leg lameness of 1-week duration. Physical examination revealed a painful swelling over the right distal femur. A radiograph of the right stifle revealed an extensive lytic lesion involving the distal metaphysis of the right femur. Cytological examination of a needle aspirate was consistent with a deep fungal infection. A pigmented dimorphic fungus was isolated in pure culture from a representative needle aspirate from the lesion. The patient improved substantially after 5 weeks of high-dose itraconazole therapy, although it was subsequently lost to follow-up.