Outbreak of acute pulmonary histoplasmosis in members of a wagon train

Area of Science:

• Environmental microbiology
• Infectious disease epidemiology
• Public health

Background:

• Histoplasmosis is a fungal infection caused by Histoplasma capsulatum, often associated with soil contaminated by bird or bat droppings.
• Outbreaks are typically linked to activities like excavation, construction, or tree removal that disturb contaminated soil.
• Migrant populations may be at increased risk due to potential exposure in new environments.

Purpose of the Study:

• To investigate an unusual outbreak of acute pulmonary histoplasmosis among a wagon train group.
• To identify the source of infection and understand the exposure pathway.
• To document the first reported outbreak in a large migrant group and its unique transmission dynamics.

Main Methods:

• Case finding and epidemiological investigation of symptomatic individuals within the wagon train group.
• Environmental sampling and laboratory culture to identify Histoplasma capsulatum in soil.
• Retrospective analysis of potential exposure sites and activities.

Main Results:

• Out of 85 wagon train participants, 69 (81%) showed evidence of Histoplasma capsulatum infection, with 54 experiencing symptomatic disease.
• The infection source was identified as a former blackbird roost in Charleston, Tennessee.
• Histoplasma capsulatum was cultured from 14 of 25 soil samples collected at the roost site.
• Exposure occurred without typical risk factors such as excavation, construction, or tree-cutting.

Conclusions:

• This outbreak highlights the risk of histoplasmosis transmission from undisturbed soil contaminated by bird droppings.
• Large migrant groups can be vulnerable to outbreaks of environmental fungal infections.
• Further research is needed to understand transmission dynamics in non-traditional exposure scenarios.