1722. Histoplasmosis Acquired in Alberta, Canada, 2011–2018

Abstract

BackgroundHistoplasmosis is a serious fungal infection caused by the geographically restricted, dimorphic fungus Histoplasma capsulatum. In Canada, the geographic range of H. capsulatum is classically thought to be restricted to southern parts of Ontario and Quebec. Over the past decade, histoplasmosis has occasionally been diagnosed in patients in Alberta without travel to areas of known geographic risk (Figure 1). We studied the epidemiology and geographic distribution of histoplasmosis in Alberta to assess evidence for locally-acquired infections.MethodsWe retrospectively reviewed all laboratory-confirmed (culture, antigen and/or immunodiffusion positive) cases of histoplasmosis diagnosed from January 1, 2011 to June 30, 2018. Data collected by public health and clinical charts were reviewed for clinical presentation, exposure and travel histories, and geographic distribution of cases. Cases of histoplasmosis in patients who had not left Alberta or associated with a local point source were classified as definite local acquisition; cases in patients with remote travel but with local exposures and appropriate timing of disease onset were deemed “probable” cases of local infection. University of Alberta’s Research Ethics Board approved this study.ResultsWe identified 45 laboratory-confirmed cases of histoplasmosis, including 17 cases that were locally acquired. Among these, there were 12 cases of definite local acquisition, including 8 patients from 3 point-source outbreaks—all involving exposure to bats and/or their droppings in chimneys or attics of private dwellings or churches—and 4 sporadic cases in patients who had never traveled. Of the other 5 cases probably acquired in Alberta, patients had previously traveled (n = 4) or travel history was incomplete (n = 1) but local exposures preceding infection were considered compelling. The mean incidence rate of locally acquired infection was 0.062/100,000 population with incidence increasing since 2014. Table 1 shows features of locally acquired cases.ConclusionThis study, for the first time, establishes Alberta as a region of geographic risk for histoplasmosis. The diagnosis should be considered in patients with compatible symptoms and exposure history, even in the absence of travel. Disclosures All authors: No reported disclosures.