Disseminated basidiobolomycosis in a dog

Case report: Localized coloproctitis caused by novel Basidiobolus arizonensis in a dog

A 6-year-old male neutered boxer mix canine was presented for a one-month history of dyschezia, hematochezia, and constipation. Colonoscopy and endoscopic biopsies revealed non-specific lymphoplasmacytic, eosinophilic colitis. Despite pursuing various therapies over a 3.5-month clinical course (including hypoallergenic diet, antibiotics, prokinetics, laxatives, and anti-inflammatory glucocorticoids), the patient's condition did not improve. Two and a half months after initial presentation, the patient developed circumferential proctitis with multiple draining tracts and obstipation. Humane euthanasia and postmortem examination were elected. Gross and histological findings revealed locally extensive pyogranulomatous coloproctitis with many intralesional PAS-positive, GMS-negative 30-40 μm in diameter, hyaline, pauciseptate, irregularly branching fungal hyphae, hyphal bodies or chlamydospores and 25-45 μm in diameter thick-walled zygospores. Fungal culture of fluid from the draining tracts was performed, and DNA sequence analysis of the ITS and partial LSU of the nuclear ribosomal RNA genes were used to identify and confirm a novel species, Basidiobolus arizonensis. Basidiobolus spp. are saprobes in the order Basidiobolales and most commonly cause granulomatous infections of the skin, respiratory tract, and gastrointestinal tract in veterinary species and humans. To the authors' knowledge, this is the first report of novel Basidiobolus arizonensis causing localized coloproctitis in a dog.

Colorectal basidiobolomycosis in a dog

A 7‐year‐old castrated male French Bulldog was examined for chronic large intestinal enteropathy. A colonic mass and thickened rectal mucosa were identified, and histopathologic examination of endoscopic biopsy specimens disclosed eosinophilic proctitis with large (5‐20 μm), irregularly shaped, pauciseptate hyphae that were Gomori methenamine silver and periodic acid‐Schiff positive. Amplification and sequencing of ribosomal DNA extracted from paraffin‐embedded tissues yielded a sequence with 97% identity to GenBank sequences for Basidiobolus ranarum. After itraconazole, terbinafine, and prednisone administration, clinical signs resolved rapidly, and sonographic lesions were largely absent after 6 weeks. Treatment was discontinued by the owner 15 weeks after diagnosis. Three weeks later, the dog collapsed acutely and was euthanized. Necropsy identified metastatic islet cell carcinoma and grossly unremarkable colorectal tissues. However, histopathology of the rectum disclosed multifocal submucosal granulomas with intralesional hyphae morphologically similar to those previously observed. This report is the first to describe medical treatment of gastrointestinal basidiobolomycosis in a dog.

Gastrointestinal pythiosis with concurrent presumptive gastrointestinal basidiobolomycosis in a Boxer dog

A 2-year-old female spayed Boxer dog was presented for a 1-month history of progressive hemorrhagic diarrhea with tenesmus and weight loss despite trial courses of antibiotics and diet change. Abdominal ultrasound revealed severe, focal thickening, and loss of normal architecture of the colonic wall with abdominal lymphadenomegaly. Dry-mount fecal cytology, performed on several consecutive days, consistently revealed numerous, round, 16-20 μm structures with basophilic, granular content, and a thin cell wall. Transmission electron microscopy identified these structures as fungi. Culture, polymerase chain reaction (PCR), and sequencing of the internal transcribed spacer, D1/D2 regions, and DNA-directed RNA polymerase II core subunit (RPB2) confirmed the presence of Basidiobolus microsporus in the feces. Biopsies collected via ileocolonoscopy revealed marked, multifocal, chronic, neutrophilic, and eosinophilic ileitis and colitis with ulceration, granulation tissue, and intralesional hyphae (identified with Gomori methenamine silver stain). A Pythium enzyme-linked immunosorbent assay and Pythium-specific PCR performed on the formalin-fixed paraffin-embedded biopsy specimens were positive while Basidiobolus-specific PCR was negative, thus confirming a diagnosis of pythiosis. This report describes a fatal case of colonic and intestinal pythiosis with the presence of fecal Basidiobolus sp. spores, suggestive of concurrent gastrointestinal basidiobolomycosis.

Gastrointestinal basidiobolomycosis in a dog

An 8-year-old, spayed, female Shiba dog was presented to a referring veterinarian with a complaint of chronic diarrhea and anorexia. Ultrasound and radiographs revealed an irregular mass in the pelvic cavity. The mass and the affected section of colon were surgically removed. Histopathological examination revealed multifocal coalescing granulomas and effaced intestinal structures. Central necrotic debris surrounded by multinucleated giant cells, lymphocytes, plasma cells and neutrophils was observed. Numerous, irregularly branched hyphae with pale basophilic, thin walls and occasional bulbous enlargements at the tips were present. Polymerase chain reaction identified Basidiobolus ranarum, successfully confirming a definitive diagnosis of basidiobolomycosis. To the best of our knowledge, this is the first report of intestinal basidiobolomycosis in a dog.

Neglected fungal zoonoses: hidden threats to man and animals

Zoonotic fungi can be naturally transmitted between animals and humans, and in some cases cause significant public health problems. A number of mycoses associated with zoonotic transmission are among the group of the most common fungal diseases, worldwide. It is, however, notable that some fungal diseases with zoonotic potential have lacked adequate attention in international public health efforts, leading to insufficient attention on their preventive strategies. This review aims to highlight some mycoses whose zoonotic potential received less attention, including infections caused by Talaromyces (Penicillium) marneffei, Lacazia loboi, Emmonsia spp., Basidiobolus ranarum, Conidiobolus spp. and Paracoccidioides brasiliensis.

Development of a specific polymerase chain reaction assay for the detection of Basidiobolus

The etiology of chronic diarrhea is complex in humans and animals. It is always necessary to evaluate a list of differential diagnosis, including bacteria, protozoa and fungi. Basidiobolomycosis is a fungal disease reported sporadically worldwide, mainly caused by B. ranarum, a frequent organism found in soil or in the intestine and skin of lizards and frogs. It is an opportunistic pathogen that causes infections characterized by granulomatous lesions in the subcutaneous tissues as well as in the intestinal wall in humans and animals. In this work we have developed a PCR technique to differentiate Basidiobolus from other causes of intestinal disease in dogs and humans. To test the specificity of the PCR assay we included closely related organisms, common intestinal microbiota and pathogenic organisms, such as Aspergillus, Candida, Cryptosporidium, Escherichia, Giardia, Mucor, Proteus, Rhizopus and Salmonella. Pythium insidiosum, which cause clinically similar disease in dogs but require a different treatment. Only Basidiobolus was positive to the PCR assay.

Outbreaks of rhinofacial and rhinopharyngeal zygomycosis in sheep in Paraíba, northeastern Brazil

Two outbreaks of zigomycosis with rhinofacial and two other with rhinopharyngeal lesions involving fungi with filamentous coaenocytic hyphae characteristic of entomoph-thoramycetous fungi are reported in the state of Paraíba, northeastern Brazil. One outbreak of rhinofacial zygomycosis occurred during the rainy season affecting 5 sheep. Another outbreak of the clinical form affected one out of 40 sheep during the dry season. Common clinical signs of the rhinofacial infection were bilateral serosanguineous nasal discharge with swelling of nostrils, upper lip, and the skin of the face. At necropsy the nasal mucosa showed dark brownish ulcerated areas which extended from the mucocutaneous region to 10cm inside the nasal vestibule. The mucosa of the hard palate was also ulcerated. The cutting surface of nostrils and palate showed a brownish or red spongeous tissue of friable consistency. One outbreak of rhinopharyngitis took place on an irrigated coconut farm; 7 out of 60 adult sheep were affected. Another outbreak affected a sheep in a flock of 80 during the dry season. Clinical signs as noisy respiration and dyspnoea due to mechanical blockage of the nasal cavities, swelling of the nostrils, and serosanguineous nasal discharge were observed. Six out of 8 sheep in this group showed exophthalmia, keratitis and unilateral corneal ulceration of the eye. The sheep either died of their infection or were euthanized after a clinical course of 7-30 days. At necropsy there was a dense yellow exudate in the nasopharyngeal area affecting the ethmoidal region, turbinate bones, paranasal sinuses, hard and soft palates, orbital cavity, pharynges, regional muscles and lymph nodes. Histopathologically both forms of the disease showed multifocal granulomas with an eosinophilic necrotic reaction (Splendore-Hoeppli phenomenon) containing ribbon-type coenocytic hyphae with 7-30mum in diameter similar to hyphae of zygomycetous fungi, possibly Conidiobolus spp. Outbreaks of both forms of mycotic rhinitis are common in northeastern Brazil and in other regions of the country.

Gastrointestinal pythiosis in two cats

Two young adult male Domestic Shorthair cats living in the southeastern United States were evaluated for signs attributable to partial intestinal obstruction. Physical examination indicated a palpable abdominal mass in each animal. Exploratory laparotomy revealed a large extraluminal mass involving the ileum and mesentery with adjacent mesenteric lymphadenopathy in cat No. 1 and an abscessed mass in the distal duodenum in cat No. 2. Mass resection and intestinal anastomosis were performed in both cats. Histologic evaluation indicated that the intestinal lesions involved primarily the outer smooth muscle layer and serosa and consisted of eosinophilic granulomatous inflammation with multifocal areas of necrosis. In Gomori methenamine silver-stained sections, broad (2.5-7.5 microm), occasionally branching, infrequently septate hyphae were observed within areas of necrosis. A diagnosis of Pythium insidiosum infection was confirmed in both cats by immunoblot serology and by immunoperoxidase staining of tissue sections using a P. insidiosum-specific polyclonal antibody. Cat No. 1 was clinically normal for 4 months after surgery but then died unexpectedly from an unknown cause. Cat No. 2 has been clinically normal for at least 9 months after surgery and appears to be cured on the basis of follow-up enzyme-linked immunosorbent assay serology.

Pythiosis, lagenidiosis, and zygomycosis in small animals

Pythiosis, lagenidiosis, and zygomycosis affect animals living in temperate, tropical, and subtropical climates, and these diseases are often fatal. Although Pythium insidiosum, Conidiobolus species, and Basidiobolus species have been recognized as pathogens for several years, members of the genus Lagenidium have been identified as a cause of oomycosis in dogs only recently. Pythiosis, lagenidiosis, and zygomycosis share similar clinical and histologic characteristics, making them difficult to distinguish from one another; however, distinguishing between these pathogens is important because of differences in epidemiology, choice and duration of therapy, and prognosis.

Infection with Basidiobolus ranarum in two dogs

Basidiobolus ranarum is a saprophytic fungus in the environment that also is a part of the endogenous microflora in the gastrointestinal tract of several vertebrates. These organisms may penetrate skin or muscosa of humans and other animals, causing granulomatous inflammation. Two dogs infected with B. ranarum had prolonged or repeated exposure to water or soil in their environment. One dog had progressive subcutaneous infection of all the limbs, and the other dog had recurrent coughing and dyspnea caused by tracheobronchitis. In both dogs, secondary bacterial infection of the lesions was evident. Treatment of the dog with subcutaneous infection involved cutaneous dressings and sequential use of enrofloxacin and itraconazole; however, this resulted in suspected liver damage without clinical improvement. Subsequent treatment with potassium iodide and a lipid formulation of amphotericin B was also unsuccessful, and the dog was euthanatized. The other dog was treated alternately with enrofloxacin and itraconazole. When the clinical signs and infection returned, combination treatment with both drugs was more effective; however, the dog developed liver damage. Subsequent treatment with enrofloxacin on an intermittent basis controlled the dog's coughing during a 3-year period.

Zygomycetes in human disease

The Zygomycetes represent relatively uncommon isolates in the clinical laboratory, reflecting either environmental contaminants or, less commonly, a clinical disease called zygomycosis. There are two orders of Zygomycetes containing organisms that cause human disease, the Mucorales and the Entomophthorales. The majority of human illness is caused by the Mucorales. While disease is most commonly linked to Rhizopus spp., other organisms are also associated with human infection, including Mucor, Rhizomucor, Absidia, Apophysomyces, Saksenaea, Cunninghamella, Cokeromyces, and Syncephalastrum spp. Although Mortierella spp. do cause disease in animals, there is no longer sufficient evidence to suggest that they are true human pathogens. The spores from these molds are transmitted by inhalation, via a variety of percutaneous routes, or by ingestion of spores. Human zygomycosis caused by the Mucorales generally occurs in immunocompromised hosts as opportunistic infections. Host risk factors include diabetes mellitus, neutropenia, sustained immunosuppressive therapy, chronic prednisone use, iron chelation therapy, broad-spectrum antibiotic use, severe malnutrition, and primary breakdown in the integrity of the cutaneous barrier such as trauma, surgical wounds, needle sticks, or burns. Zygomycosis occurs only rarely in immunocompetent hosts. The disease manifestations reflect the mode of transmission, with rhinocerebral and pulmonary diseases being the most common manifestations. Cutaneous, gastrointestinal, and allergic diseases are also seen. The Mucorales are associated with angioinvasive disease, often leading to thrombosis, infarction of involved tissues, and tissue destruction mediated by a number of fungal proteases, lipases, and mycotoxins. If the diagnosis is not made early, dissemination often occurs. Therapy, if it is to be effective, must be started early and requires combinations of antifungal drugs, surgical intervention, and reversal of the underlying risk factors. The Entomophthorales are closely related to the Mucorales on the basis of sexual growth by production of zygospores and by the production of coenocytic hyphae. Despite these similarities, the Entomophthorales and Mucorales have dramatically different gross morphologies, asexual reproductive characteristics, and disease manifestations. In comparison to the floccose aerial mycelium of the Mucorales, the Entomophthorales produce a compact, glabrous mycelium. The asexually produced spores of the Entomophthorales may be passively released or actively expelled into the environment. Human disease with these organisms occurs predominantly in tropical regions, with transmission occurring by implantation of spores via minor trauma such as insect bites or by inhalation of spores into the sinuses. Conidiobolus typically infects mucocutaneous sites to produce sinusitis disease, while Basidiobolus infections occur as subcutaneous mycosis of the trunk and extremities. The Entomophthorales are true pathogens, infecting primarily immunocompetent hosts. They generally do not invade blood vessels and rarely disseminate. Occasional cases of disseminated and angioinvasive disease have recently been described, primarily in immunocompromised patients, suggesting a possible emerging role for this organism as an opportunist.

Zygomycetes in human disease

The Zygomycetes represent relatively uncommon isolates in the clinical laboratory, reflecting either environmental contaminants or, less commonly, a clinical disease called zygomycosis. There are two orders of Zygomycetes containing organisms that cause human disease, the Mucorales and the Entomophthorales. The majority of human illness is caused by the Mucorales. While disease is most commonly linked to Rhizopus spp., other organisms are also associated with human infection, including Mucor, Rhizomucor, Absidia, Apophysomyces, Saksenaea, Cunninghamella, Cokeromyces, and Syncephalastrum spp. Although Mortierella spp. do cause disease in animals, there is no longer sufficient evidence to suggest that they are true human pathogens. The spores from these molds are transmitted by inhalation, via a variety of percutaneous routes, or by ingestion of spores. Human zygomycosis caused by the Mucorales generally occurs in immunocompromised hosts as opportunistic infections. Host risk factors include diabetes mellitus, neutropenia, sustained immunosuppressive therapy, chronic prednisone use, iron chelation therapy, broad-spectrum antibiotic use, severe malnutrition, and primary breakdown in the integrity of the cutaneous barrier such as trauma, surgical wounds, needle sticks, or burns. Zygomycosis occurs only rarely in immunocompetent hosts. The disease manifestations reflect the mode of transmission, with rhinocerebral and pulmonary diseases being the most common manifestations. Cutaneous, gastrointestinal, and allergic diseases are also seen. The Mucorales are associated with angioinvasive disease, often leading to thrombosis, infarction of involved tissues, and tissue destruction mediated by a number of fungal proteases, lipases, and mycotoxins. If the diagnosis is not made early, dissemination often occurs. Therapy, if it is to be effective, must be started early and requires combinations of antifungal drugs, surgical intervention, and reversal of the underlying risk factors. The Entomophthorales are closely related to the Mucorales on the basis of sexual growth by production of zygospores and by the production of coenocytic hyphae. Despite these similarities, the Entomophthorales and Mucorales have dramatically different gross morphologies, asexual reproductive characteristics, and disease manifestations. In comparison to the floccose aerial mycelium of the Mucorales, the Entomophthorales produce a compact, glabrous mycelium. The asexually produced spores of the Entomophthorales may be passively released or actively expelled into the environment. Human disease with these organisms occurs predominantly in tropical regions, with transmission occurring by implantation of spores via minor trauma such as insect bites or by inhalation of spores into the sinuses. Conidiobolus typically infects mucocutaneous sites to produce sinusitis disease, while Basidiobolus infections occur as subcutaneous mycosis of the trunk and extremities. The Entomophthorales are true pathogens, infecting primarily immunocompetent hosts. They generally do not invade blood vessels and rarely disseminate. Occasional cases of disseminated and angioinvasive disease have recently been described, primarily in immunocompromised patients, suggesting a possible emerging role for this organism as an opportunist.

Subcutaneous phycomycosis caused by Basidiobolus haptosporus: a clinicopathologic and mycologic study in a child

The clinical, histopathologic, and mycologic aspects of a case of subcutaneous phycomycosis caused by Basidiobolus haptosporus in a 3-year-old boy are reported. This is the first documented case from Central and North America. Oral potassium iodide and trimethoprim-sulfamethoxazole gave excellent therapeutic results.

Parasitic adaptation of pathogenic fungi to mammalian hosts

Pathogenic fungi involved in medical and veterinary mycology can be classified in three different groups according to their level of adaptation to parasitism. Only a few species belonging to dermatophytes can be considered genuine parasites as opposed to molds or fungi involved in systemic mycoses. Ecological, ethological, biochemical, and immunological factors can play a role in preadaptation or adaptation to parasitic life and are discussed.

Immunology of fungal infections in animals

The nature of immunity to fungal infection is discussed predominantly for mammals and birds. T-cell-mediated immunity seems essential for recovery both from cutaneous and mucosal infections (Candida, Malassezia and dermatophytes) and from infections of systemic fungal pathogens (Cryptococcus, Blastomyces, Histoplasma, and Coccidioides). Often chronic progressive disease caused by these fungi is associated with a depression or absence of T-cell-mediated immunity to antigens of the infecting fungus. In contrast recovery from disease, or absence of clinical disease after exposure to these fungi, is associated with the presence of strong T-cell-mediated immune responses to the fungus. The activation of macrophages and the stimulation of epidermal growth and keratinization are the processes induced by T-cell-mediated immunity which result in the resolution of systemic or cutaneous and mucosal disease. Other cell types, for example NK cells and PMNs (polymorphonuclear leucocytes), may be important in these diseases in reducing the effective amount of inoculum to which an animal is exposed and thereby reducing the likelihood of disseminated disease. Invasive opportunistic fungi (Candida, Aspergillus, Mucorales) are resisted by PMNs which attach to the hyphae or pseudohyphae and damage them via an extracellular mechanism. Other host cell types may be important in natural resistance, fungal spores being handled by the macrophages which, under conditions when animals are not immunosuppressed, are likely to be an effective first line of defense. Subcutaneous pathogens and miscellaneous other fungal diseases are discussed from a point of view of host immunity and immunodiagnosis. Vaccine development for ringworm and for other mycoses is discussed.