Bat excrement-filled tunnels cause deadly outbreak in Dominican Republic
Tunnels filled knee-high with bat guano caused a deadly outbreak of histoplasmosis in the Dominican Republic, raising awareness of what may be an underdiagnosed infection in Latin America, investigators said.


The outbreak occurred in 2015 among 36 men who were hired to clean the bat excrement from several long access tunnels leading to a hydroelectric dam, according to findings from a CDC-led investigation that were published in Clinical Infectious Diseases. The tunnels, which allow access for inspection and maintenance of the dam, were home to large colonies of bats and had not been cleaned in decades, Paige A. Armstrong, MD, MPH, medical epidemiologist in the Rickettsial Zoonoses Branch of the CDC’s Division of Vector-Borne Diseases, and colleagues reported.

Twenty-eight men were hospitalized in the outbreak, including nine who required intensive care, and three died. The men likely became infected by breathing instirred-up fungal spores while working without proper respiratory protection in the dark, hot tunnels, the investigators said.

Although the fungi responsible for the infections, Histoplasma capsulatum, is endemic to the Caribbean, and histoplasmosis is diagnosed in travelers returning from the Dominican Republic, this was the first outbreak reported on the island. However, Armstrong and colleagues said previous cases and outbreaks may simply have gone unnoticed.

“These were likely not the first cases of histoplasmosis in the Dominican Republic,” Armstrong told Infectious Disease News. “Identifying cases ... can be challenging, usually requiring special diagnostic methods.”

The investigators said clinicians in the Dominican Republic were largely unfamiliar with histoplasmosis before the outbreak and no laboratory had the capacity to definitively diagnose it. But Armstrong said investigators believe the outbreak increased awareness among health care providers about the disease.

“Throughout this investigation, we worked closely with partners from the CDC Dominican Republic office and the ministries of health and labor,” she said. “Efforts are ongoing to expand education and diagnostic capacity for histoplasmosis in the country.”

Request for help

H. capsulatum live in the environment, particularly in soil containing large amounts of bird or bat droppings, according to the CDC. Most people who breathe in the spores never have symptoms. Armstrong and colleagues said delays in recognition and treatment in the 2015 outbreak likely contributed to an unusually high proportion of hospitalizations and deaths among the tunnel workers.

Health officials in the Dominican Republic asked the CDC on Sept. 16, 2015, to help determine what caused an outbreak of an unknown severe febrile illness. Upon arriving, investigators — including Armstrong, then an officer in the CDC’s Epidemic Intelligence Service — looked at company payrolls to find workers who had been in the tunnels and reviewed records from the hospitals where they were treated. During their investigation, they interviewed workers who were still living and the immediate family members of those who had died.

They said patients were initially treated for leptospirosis, a bacterial disease endemic to the region, but their infections did not respond to penicillin. Physicians notified local health officials about the illnesses and the patients’ common exposure to tunnel work.

“At one regional facility, an astute physician, who had treated cases of histoplasmosis while training in Mexico, suggested the diagnosis of histoplasmosis given its association with exposure to bat guano,” Armstrong and colleagues wrote. “The same day, a pathologist noted yeast cells, suggestive of H. capsulatum by microscopy on a bronchoalveolar lavage specimen.”

‘Poop up to their knees’

The tunnel workers had been recruited informally by a private company that was contracted to clean the tunnels, according to Armstrong and colleagues. They were provided with knee-high rubber boots, a hard hat with an attached headlamp and shovels for removing the guano. Some also received loose-fitting paper surgical masks, but almost half of the workers never used them, and only three reported using them all the time.

The men reported working in oppressive heat and having difficulty breathing while wearing the masks inside the tunnel. They worked several hours a day, 5 days a week from July 30 to Sept. 2, 2015.

In their report, Armstrong and colleagues said that up to more than 3 feet of guano had accumulated in the tunnels since the last time they had been accessed 30 years ago. In a previous interview with Infectious Disease News, Armstrong described the men working in tunnels “filled with bat poop up to their knees.”

Work in the tunnels was stopped when some of the men became sick, Armstrong and colleagues reported. In addition to delayed diagnoses, they said patients either did not receive treatment with the recommended antifungal, amphotericin B, or their treatment was delayed. In all, 22 of the 34 men who were tested had laboratory evidence of H. capsulatum infection, and 30 had illnesses that met the case definition of infection.

“This outbreak adds to evidence that histoplasmosis is underdiagnosed in Latin America and the Caribbean,” Armstrong and colleagues concluded. “Increased awareness of the disease among clinicians and public health officials, improved diagnostic capacity and access to antifungals is essential in helping to prevent severe illness and death. Occupational health precautions during higher risk activities, particularly those involving disturbances to bird and bat guano, could reduce worker exposure to H. capsulatum.

“Because workers are often at higher risk of exposure than the general population,” they continued, “the identification of high-risk environments as well as the implementation of appropriate engineering and administrative controls and adequate personal protective equipment may help to prevent similar outbreaks in the future.” – by Gerard Gallagher

Go back | Date: 05 Jan 2018
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