Blastomyces helicus, an Emerging Dimorphic Fungal Pathogen Causing Fatal Pulmonary and Disseminated Disease in Humans and Animals in Western Canada and United States

Abstract

Background Blastomyces helicus (formerly Emmonsia helica) is a recently described dimorphic fungus first isolated from a man who died of encephalitis in Alberta, Canada. The geographic range, epidemiology and clinical features are unknown.Methods We reviewed clinical and veterinary isolates of Blastomyces and Emmonsia at the University of Alberta Microfungus Collection and Herbarium and the UT Health San Antonio Fungus Testing Laboratory. Isolates were selected based on low B. dermatitidis DNA probe values and/or atypical morphology. DNA sequence analysis was performed. Epidemiological and clinical data were analyzed.ResultsIsolates of B. helicus were identified from eight human (Table 1) and five veterinary cases (Table 2). Mycelial and yeast-like phases of typical clinical isolates are shown in Figures 1 and 2, respectively. Isolates were referred from provinces and states shown in Figure 3.Table 1:Clinical isolates of Blastomyces helicusCase/yearLocationMedical historySampleOutcomec1/1970AlbertaAlcoholism, diabetesCerebrospinal fluid (CSF), lungFatalc2/1992SaskatchewanChronic leukemia, steroidsBlood, bone marrow, liver, sputumFatalc3/1999TexasLupusBloodUnknownc4/2004AlbertaUnknownBronchoalveolar lavage (BAL), bloodUnknownc5/2010CaliforniaLiver transplantBlood, pleural fluidFatalc6/2010TexasUnknownCSFUnknownc7/2010CaliforniaHIVBALUnknownc8/2017NebraskaUnknownBAL, pleural fluidUnknownTable 2:Veterinary isolates of Blastomyces helicusCase/yearLocationAnimalSamplev1/2005ColoradoDogLungv2/2007UnknownDogLungv3/2009MontanaCatLungv4/2012ColoradoCatLungv5/2014ColoradoUnknownLungFigure 1.Mycelial phase of B. helicus (c2) at 25C showing typical helically coiled hyphae and absence of conidia.Figure 2.Yeast-like phase of B. helicus (c1) at 35C showing typical variably sized yeast-like cells in chains.Figure 3.Canadian provinces and US states from where Blastomyces helicus isolates were referreConclusion Blastomyces helicus caused pulmonary and fatal disseminated disease, mainly in immunocompromised persons, and lung disease in companion animals in western Canada and US. Epidemiological investigations are needed to establish the burden of disease and geographic range of this pathogen.Disclosures All authors: No reported disclosures.