[Bird Management] Histoplasmosis & Human Health

A report last year from the Centers for Disease Control and Prevention should remind us of the importance of managing urban bird and bat populations. In the Dec. 19, 2008, edition of the Morbidity and Mortality Weekly Report (MMWR), there was a report about a Pennsylvania-based church mission group that had been renovating a church in Nueva San Salvador, El Salvador. It turns out that part of the renovations involved cleaning and sweeping around some bird and bat roosting areas. Nine of the 11 persons with the initial group returned home with flu-like symptoms. The symptoms were eventually diagnosed as histoplasmosis, a disease caused by inhaling the spores of a fungus, Histoplasma capsulatum. Eventually 11 more volunteers from two other missions groups from Pennsylvania and Virginia, working at the same church at approximately the same time (February/March 2008), also met the case definition for the disease.

Histoplasmosis is a pest-borne disease that PMPs often hear about, but rarely encounter (at least knowingly). The pathogen is common in the U.S., and it is probably more common than most realize.

The fungus lives in soil, and people typically become infected when they breath dust from soil in areas where H. capsulatum naturally occurs. According to NIOSH publication 2005-1009, H. capsulatum is endemic throughout the U.S., although the proportion of people infected by H. capsulatum is higher in central and eastern states, especially along the Ohio and Mississippi River valleys. Fortunately, once contracted the disease is not contagious.

The interesting thing about this disease, from the perspective of the PMP, is that the fungus seems to grow best in soils having a high nitrogen content, especially those enriched with bird manure or bat droppings. The organism is believed to be carried on the wings, feet and beaks of birds, thereby increasing the risk of infected soil under bird or bat roosting sites or in manure accumulations inside or outside buildings. Some bird species whose roosts have been shown to be contaminated include blackbirds (starlings, grackles, red-winged blackbirds and cowbirds), pigeons, chickens and bats. Some are concerned that growing problems with Canada geese could also be contributing to spread of the disease to people.

Because the fungus cannot infect birds, there appears to be little risk of contracting this disease from bird droppings on window ledges or inside buildings. It’s only when these droppings contact infested soil that the fungus is able to spread and become a health risk.

Bats are a different story because according to the CDC, they can become infected with the pathogen. So bat droppings can be potential sources for infection.

How bad is it? Histoplasmosis symptoms vary greatly. Most people who contract the disease show no, or only mild, symptoms. In some of us, histoplasmosis will result in flu-like, respiratory symptoms, including a general feeling of illness (malaise), fever, chest pain, dry or nonproductive cough, headache, loss of appetite, shortness of breath, joint and muscle pains, chills, and hoarseness. In some cases, the disease can become chronic and result in more serious complications, even death.

Histoplasmosis may not be one of the most serious diseases we will be exposed to during our lifetimes, but because it is rarely diagnosed, it probably causes more lost work days that we realize. And it is certainly able to make us sick enough to miss work.

What should PMPs do? The first concern of a pest management professional who encounters bird or bat infestations is to take steps to reduce the risk of breathing H. capsulatum spores. When working in dusty areas with bird or bat droppings, a good respirator should be worn. All it takes to cause infection and subsequent development of histoplasmosis is a brief exposure to inhaled contaminated dust. Remember that not all air filtering devices are equal and people have developed histoplasmosis after disturbing material contaminated with H. capsulatum despite wearing either a respirator or a mask that they assumed would protect them.

In addition to breathing protection, the CDC recommends disposable overalls. This reduces the risk of worker and family exposure to dust that settles on clothing during exposure to contaminated soil.

Knowing how to protect your customers is also critical. In areas where public access is minimal, or where remediation of droppings is taking place, the posting of signs warning people about histoplasmosis risk is a prudent first step. Anywhere that bird droppings sit on soil should be considered a high risk site for histoplasmosis. The public and unprotected workers also should be restricted from any areas with bat guano accumulations.

Areas that are being cleaned up should be sprayed with water to minimize dust movement. Obviously bird and bat control, and modification of the roosting environment are critical elements in reducing the long-term risks associated with this disease and others.

Histoplasmosis is only one disease risk caused by bird and bat roosts around human activity areas. While we shouldn’t fear or loath birds and bats in natural settings, management of their roosting areas in urban locations are an important part of what our industry does.

The author has been an entomology specialist for Texas AgriLife Extension since 1989. Contact him via e-mail at mmerchant@giemedia.com.

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Safety Precautions in Roosts

• Wear a respirator equipped with a high-efficiency (HE) 100 series filter (purple) to block particles down to 0.3 microns to protect yourself from airborne spores and cells.
• Wear protective gloves, hat, coveralls and boots. Disposable is best.
• Turn off any and all HVAC systems in the area.
• Wet down the droppings to keep spores and cells from becoming airborne. Keep the droppings wet at all times. If you notice dust becoming airborne, use an electric “fogger” to spray water into the air to settle out airborne dust particles and any spores that might be present.
• Put the wet droppings into sealed plastic garbage bags and wet down the outside of the bags.
• When finished, and while still wearing the respirator, walk away from the site, remove protective clothing and place it in a plastic bag. Reusable clothing should be kept wet at all times until it is washed. There is some risk to the person washing the clothes; this is another reason disposable clothing is best.
• Dispose of trash bags. Disposal should be permitted in the local landfill. To avoid potential dispersal of spores along the road, bags should be transported whole and sealed, not left for trash pickup where they could be broken by compacting inside a standard trash truck.
• Wash up or shower on site.
• Wash off your respirator.

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Editor’s note: This information was adapted from Techletter, a biweekly publication from Pinto & Associates, Mechanicsville, Md. To subscribe, visit www.techletter.com, or call 301/884-3020.