Blastomycosis in New England: 5 Cases and a Review

Outcomes Associated With Blastomycosis in Solid Organ and Hematopoietic Cell Transplant Recipients

INTRODUCTION

With reports of expanding epidemiology of blastomycosis across the United States, the purpose of this study was to evaluate the incidence and outcomes associated with blastomycosis in solid organ transplant (SOT) and hematopoietic cell transplant (HCT) recipients.

METHODS

We conducted a retrospective case series of adult SOT and HCT recipients at a tertiary care medical center between January 1, 2005 and September 30, 2023. Cases were defined as culture-proven blastomycosis. We performed descriptive statistical analysis to evaluate diagnosis, management, and outcomes (mortality) of blastomycosis in SOT.

RESULTS

The cumulative incidence of blastomycosis was 0.11% with a median time to infection following transplant of 743 days. Of the 19 cases, the majority of patients were SOT recipients (90%). Supratherapeutic immunosuppression within 30 days of diagnosis was observed in 42% of cases with documented drug monitoring. Urine antigen testing was highly sensitive (100%). Fourteen (73.7%) patients received induction therapy with liposomal amphotericin B followed by azole therapy for a minimum of 12 months. Despite appropriate treatment, 1-year mortality was high at 26.3%, with attributable mortality of 21.1%.

CONCLUSIONS

While rates of blastomycosis remain low among SOT and HCT recipients, infection is associated with poor posttransplant outcomes. Antigen testing can aid in timely assessment of disease severity and initiation of appropriate therapy. Among survivors, no relapses were observed while on lifelong secondary suppression. Future studies should aim to better define risk factors associated with developing blastomycosis and establish effective strategies for prevention.

A case of disseminated blastomycosis in New England

Blastomyces infections are classified as dimorphic fungal infections commonly seen geographically throughout the Mississippi and Ohio River Valleys, St. Laurence Seaways, as well as the Canadian providences of Ontario Manitoba, and Saskatchewan. Although primarily endemic in the Midwestern United States, there has been a rise in cases throughout New England. Factors that could contribute to this rise of blastomycosis include a changing climate, increasing use of immunosuppressive medications as well as a greater recognition of this disease. Initial presentation of blastomycosis follows the inhalation of fungal spores which can cause flu-like symptoms or mimic acute pneumonia. Blastomycosis can also present as a disseminated infection through extrapulmonary spread in both immunocompromised and immunocompetent hosts and cases present at similar rates within the population. Here we present a case of disseminated blastomycosis in a patient from New England with no reported pre-existing risk factors. The patient developed blastomycosis osteomyelitis in the left elbow which prompted surgical intervention as well as a 12-month regimen of voriconazole therapy. This case outlines the need to adopt better surveillance practices for blastomycosis in non-endemic areas as well as highlights the imperative role of healthcare staff in implementing proper reporting measures to track the spread of blastomycosis.

Perspectives on blastomycosis in Canada in the face of climate change

Blastomycosis is a disease of potentially varied presentations caused by thermally dimorphic fungi that appear as mold at ambient temperatures and transform to yeast at body temperature. Inhalation of aerosolized fungal spores represents the primary mode of transmission. Exposure may follow outdoor activities that disturb soil, which is warm, moist, acidic and rich in organic debris, particularly within forested areas and in proximity to waterways. Blastomycosis is endemic to several parts of Canada, but is only reportable in Ontario and Manitoba, with Northwestern Ontario being considered a hyperendemic area with average annual incidence rates of over 25 cases per 100,000 population. Delays in diagnosis and treatment are frequently observed as the symptoms and imaging findings of blastomycosis may initially be mistaken for community-acquired pneumonia, tuberculosis or malignancy, which can result in interim disease progression and worsening clinical outcomes. Risks from fungal infections such as blastomycosis are likely to increase with climate change-associated shifts in temperature and rainfall, and this may contribute to the geographic expansion of cases, a phenomenon that appears to be already underway. Further research investigating the ecological niche of Blastomyces and its climate sensitivity could help facilitate better modelling of the potential impacts of climate change on risks to Canadians and inform more effective methods of exposure prevention. Early clinical recognition and treatment of blastomycosis remain the key to minimizing morbidity and mortality.

Impact of climate change and natural disasters on fungal infections

The effects of climate change and natural disasters on fungal pathogens and the risks for fungal diseases remain incompletely understood. In this literature review, we examined how fungi are adapting to an increase in the Earth's temperature and are becoming more thermotolerant, which is enhancing fungal fitness and virulence. Climate change is creating conditions conducive to the emergence of new fungal pathogens and is priming fungi to adapt to previously inhospitable environments, such as polluted habitats and urban areas, leading to the geographical spread of some fungi to traditionally non-endemic areas. Climate change is also contributing to increases in the frequency and severity of natural disasters, which can trigger outbreaks of fungal diseases and increase the spread of fungal pathogens. The populations mostly affected are the socially vulnerable. More awareness, research, funding, and policies on the part of key stakeholders are needed to mitigate the effects of climate change and disaster-related fungal diseases.

Using Insurance Claims Data to Estimate Blastomycosis Incidence, Vermont, USA, 2011-2020

The epidemiology of blastomycosis in Vermont, USA, is poorly understood. Using insurance claims data, we estimated the mean annual blastomycosis incidence was 1.8 patients/100,000 persons during 2011-2020. Incidence and disease severity were highest in north-central counties. Our findings highlight a need for improved clinical awareness and expanded surveillance.

Blastomycosis-Associated Hospitalizations, United States, 2010-2020

BACKGROUND

Blastomycosis is an environmentally acquired fungal disease that can cause severe illness, with approximately 65% of reported cases requiring hospitalization. Recent trends in blastomycosis-associated hospitalizations in the United States have not been described.

METHODS

We analyzed hospital discharge data from the Healthcare Cost and Utilization Project (HCUP) National (Nationwide) Inpatient Sample. We calculated hospitalization rates per 100,000 population using U.S. census data and examined factors associated with in-hospital mortality.

RESULTS

An estimated 11,776 blastomycosis-associated hospitalizations occurred during 2010-2020 (average yearly rate 0.3 per 100,000 persons), with no apparent temporal trend. Rates were consistently highest among persons ≥65 years old and males. In-hospital death occurred in 7.9% and approximately doubled from 3.9% in 2010 to 8.5% in 2020. Older age, chronic obstructive pulmonary disease, and malignancy were associated with mortality.

CONCLUSIONS

Blastomycosis-associated hospitalizations can result in poor outcomes, underscoring the continued need for attention to early detection and treatment of blastomycosis and monitoring of disease trends.