New Risk Factor for Histoplasmosis: Bamboo Bonfires

Laurie Barclay, MD

February 27, 2014

A histoplasmosis case cluster in Arkansas in October 2011 suggests that exposure to a bamboo bonfire may be a new risk factor clinicians should ask about when a patient presents with characteristic symptoms, according to a report published in the February 28 issue of the Morbidity and Mortality Weekly Report. The investigators point out that heating of spores may potentially increase transmission efficiency and could create a local outbreak among persons exposed to burning bamboo containing bird feces.

"Histoplasmosis is endemic in Arkansas and many states along the Ohio, Mississippi, and Missouri river valleys," write Dirk T. Haselow, MD, PhD, from the Arkansas Department of Health, and colleagues. "This is the first outbreak of histoplasmosis associated with a bamboo bonfire reported in Arkansas. A previous report from Louisiana in 1980 linked histoplasmosis to the clearing of a field of bamboo measuring 40 feet by 70 feet that was heavily laden with blackbird feces."

Previous outbreaks have been associated with disturbed ground, bird feces, or bat guano. In the present outbreak, a cluster of acute histoplasmosis cases occurred among persons who attended a bonfire using bamboo that previously served as a blackbird roost. The bonfire was the only common exposure in the cluster.

A retrospective cohort study showed that among 19 attendees at the family gathering where the bonfire occurred, 7 were confirmed with histoplasmosis, 11 were probable cases, and only 1 did not have histoplasmosis. In Arkansas, confirmed cases must have a measured temperature of 101°F or higher (38.3°C or higher); cough, chest pain, shortness of breath, or abnormal chest radiography; and at least 1 positive culture, antigen, or serologic test for Histoplasma.

Antifungal Treatment Effective

The index cases were a boy aged 8 years and his 5-year-old sister, who initially had vague abdominal pain and a dry cough, followed by high fever and nonbloody emesis, as well as worsening cough productive of white sputum. Chest radiographs showed bilateral diffuse infiltrative disease and micronodular density patterns, as well as mediastinal lymphadenopathy.

Both children responded dramatically to empiric antifungal treatment with itraconazole, 5 mg/kg per dose twice daily, and they defervesced within 48 hours. Both had positive Histoplasma yeast and mycelial antibodies and positive serum antigen results. After 3 months of itraconazole treatment for acute diffuse pulmonary histoplasmosis, repeat chest radiographs showed resolution of acute lung findings.

Of the 18 attendees with probable or confirmed histoplasmosis, 7 were hospitalized, 7 were treated with itraconazole, and 2 had self-limited disease. All recovered.

Limitations of this investigation include possible overestimation of cases, as ill persons who did not have definitive testing were considered as probable cases, as well as insufficient data to determine statistically significant findings relating to an exposure at the site to acute histoplasmosis.

"Because all attendees in both outbreaks reported illness, this raises the possibility that heating of Histoplasma spores in conjunction with fire-related air currents might create an ideal mode of transmission," the report authors conclude. "Additional research on heating and desiccation on mold particle size and infectivity might be warranted."

The authors have disclosed no relevant financial relationships.

Morb Mortal Wkly Rep. 2014;63:165-168.


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