Clinical and molecular epidemiology of veterinary blastomycosis in Wisconsin

Analysis and modeling of Blastomyces dermatitidis environmental prevalence in Minnesota using soil collected to compare basal and outbreak levels

Outbreaks of blastomycosis, caused by the fungus Blastomyces dermatitidis, occur in endemic areas of the United States and Canada but the geographic range of blastomycosis is expanding. Previous studies inferred the location of B. dermatitidis through epidemiologic data associated with outbreaks because culture of B. dermatitidis from the environment is often unsuccessful. In this study, we used a culture-independent, PCR-based method to identify B. dermatitidis DNA in environmental samples using the BAD1 promoter region. We tested 250 environmental samples collected in Minnesota, either associated with blastomycosis outbreaks or environmental samples collected from high- and low-endemic regions to determine basal prevalence of B. dermatitidis in the environment. We identified a fifth BAD1 promoter haplotype of B. dermatitidis prevalent in Minnesota. Ecological niche analysis identified latitude, longitude, elevation, and site classification as environmental parameters associated with the presence of B. dermatitidis Using this analysis, a Random Forest model predicted B. dermatitidis presence in basal environmental samples with 75% accuracy. These data support use of culture-independent, PCR-based environmental sampling to track spread into new regions and to characterize the unknown B. dermatitidis environmental niche.Importance Upon inhalation of spores from the fungus Blastomyces dermatitidis from the environment, humans and animals can develop the disease blastomycosis. Based on disease epidemiology, B. dermatitidis is known to be endemic in the United States and Canada around the Great Lakes and in the Ohio and Mississippi River Valleys but is starting to emerge in other areas. B. dermatitidis is extremely difficult to culture from the environment so little is known about the environmental reservoirs for this pathogen. We used a culture-independent PCR-based assay to identify the presence of B. dermatitidis DNA in soil samples from Minnesota. By combining molecular data with ecological niche modeling, we were able to predict the presence of B. dermatitidis in environmental samples with 75% accuracy and to define characteristics of the B. dermatitidis environmental niche. Importantly, we showed the effectiveness of using a PCR-based assay to identify B. dermatitidis in environmental samples.

Occurrence of various pathogenic and opportunistic fungi in skin diseases of domestic animals: a retrospective study

Background

Fungal infection of animals or humans are common all over the world. Some of microorganisms like fungi, exist on the skin and can be transmitted onto other individuals, other animal species or even humans and cause skin infections. Moreover, they can be the causative agents of severe generalized infections especially in immunocompromised individuals. The study aimed to evaluate the most frequent etiological agents of skin diseases and to compare the prevalence of animal fungal infections in Poland, and to discuss the possibility of transmission to humans in Poland.

Results

The obtained results are culture based. The fungi most frequently isolated from group of animals with skin lesions were Malassezia pachydermatis (29.14%), and Candida yeasts (27.07%), and dermatophytes (23.5%), including Microsporum canis as majority of them (59.25%), and Trichophyton genus (40.7%), most of them T. mentagrophytes, while Malassezia pachydermatis represented (80%) of isolates in animals with otitis externa. In over 19% of positive fungal cultures obtained from external ear canals Candida yeasts, mainly C. albicans, were identified.

Conclusions

Dermatomycoses in companion animals are caused by both, mycelial fungi and yeasts. Most frequently isolated were Malassezia pachydermatis and Candida spp. Dermatophytes (Trichophyton, Microsporum), were also cultured, but the total number of these isolates seems to decrease. We have not found Cryptococcus neoformans in tested clinical samples.

Re-drawing the Maps for Endemic Mycoses

Endemic mycoses such as histoplasmosis, coccidioidomycosis, blastomycosis, paracoccidioidomycosis, and talaromycosis are well-known causes of focal and systemic disease within specific geographic areas of known endemicity. However, over the past few decades, there have been increasingly frequent reports of infections due to endemic fungi in areas previously thought to be “non-endemic.” There are numerous potential reasons for this shift such as increased use of immune suppressive medications, improved diagnostic tests, increased disease recognition, and global factors such as migration, increased travel, and climate change. Regardless of the causes, it has become evident that our previous understanding of endemic regions for these fungal diseases needs to evolve. The epidemiology of the newly described Emergomyces is incomplete; our understanding of it continues to evolve. This review will focus on the evidence underlying the established areas of endemicity for these mycoses as well as new data and reports from medical literature that support the re-thinking these geographic boundaries. Updating the endemic fungi maps would inform clinical practice and global surveillance of these diseases.

Concurrent cranial mediastinal Blastomyces granuloma and carcinoma with cranial vena caval syndrome in a dog

This report describes an unusual progression of blastomycosis in a dog with concurrent mediastinal carcinoma. The dog was evaluated for respiratory distress. Diagnostic results revealed chylothorax and a cranial vena caval thrombus. Histopathology of the cranial mediastinal mass diagnosed mediastinal carcinoma and fungal granuloma. Intercurrent disease may complicate the clinical presentation and clinical course of blastomycosis.

Disseminated Blastomyces dermatitidis, genetic group 2, infection in an alpaca (Vicugna pacos)

A 7-year-old, female Huacaya alpaca presented with a 3-week history of left-sided head tilt and mild ataxia. Despite aggressive supportive therapy with empirical antibiotic, anti-inflammatory, thiamine, and anthelminthic therapy, neurologic signs progressed to a right-sided head tilt, positional nystagmus, and episodes of severe ataxia and obtundation. On necropsy, discrete expansile to poorly delineated infiltrative masses with tan, creamy to grumous exudate were observed in the right petrous temporal bone, right middle and inner ear, right cerebellum and medulla as well as in lung, kidney, liver, spleen, lymph nodes, and the gastrointestinal tract. Impression cytology and histology revealed a myriad of intralesional yeast, 10-25 μm in diameter, with double-contoured walls, granular protoplasm, and broad-based budding. Culture characteristics, including conidial morphology and temperature-dependent yeast phase transformation, were consistent with Blastomyces sp. Positive Blastomyces antigenuria was identified on a postmortem sample of urine. Microsatellite typing and sequencing of the internal transcribed spacer region 2 identified the infecting strain as a genetic group 2 isolate of Blastomyces dermatitidis. The present report of camelid blastomycosis adds intracranial blastomycosis to the differential list for camelid neurologic disease in endemic regions.