Precautions Help Prevent Histoplasmosis

HISTOPLASMOSIS RISK. Many pest management professionals routinely question whether or not they are at risk for histoplasmosis when entering attics and other enclosed areas where birds or bats may be roosting or roosted at an earlier time.

Of course, the concern is valid. Within the past year, the National Institute of Occupational Safety and Health published a booklet titled “Histoplasmosis: Protecting Workers at Risk.” This publication provides an outstanding update on histoplasmosis as well as other diseases associated with bird and bat roosts, including cryptococcosis and psittacosis.

The NIOSH publication lists “pest control workers” among those that need to be specifically attentive to the proper procedures and protections against diseases associated with bird and bat roosts. No surprise here. What is surprising is the large number of pest management professionals who are not aware of (or are indifferent regarding) the pathogens associated with both active and inactive bird and bat roosts.

Histoplasmosis infection occurs when fungal spores, carried by the air (aerosolized), are inhaled after an infected roost has been “disturbed.” General pest inspections and treatments done in infected attics and buildings during urban wildlife control operations can cause such disturbances.

Histoplasmosis is more prevalent in some parts of the country than others. The states drained by the Mississippi and Ohio Rivers have relatively high incidences, but histoplasmosis is also present in several central, southeastern and mid-Atlantic states.

Indianapolis for example, has had three major histoplasmosis outbreaks — in 1979, 1980 and 1988 — and all were associated with building demolition or construction operations. In some of the high-incident areas, up to 80% of the population showed evidence of previous infection, but the majority was asymptomatic. Still, most state health officials consider this disease “uncommon.”

WHERE TO FIND IT. The most serious concerns for histoplasmosis are associated with large infestations of birds which have been established in the same area for two or more years. Moreover, the histoplasmosis organisms flourish when the bird droppings are associated with soil that has been enriched by bird droppings. Thus, outside roosts of blackbirds and starlings in tree stands for several years are more likely to be a histoplasmosis threat than the recent pigeon infestation at the local shopping mall. In other words, it is not likely that an attic that has a new and/or minor pigeon or bat infestation is a major histoplasmosis threat. Moreover, H. capsulatum is not found in fresh bird droppings because apparently, the fresh droppings are too acidic for the fungus to develop.

Bat roosts are also of concern because histoplasmosis has been found in a few bat infestations inside buildings. But overall, the incidence of histoplasmosis being transmitted from bat droppings to humans is also not thought to be high. An important difference, however, is that unlike fresh bird droppings, histoplasmosis can be present in fresh bat droppings.

So where does this lead us relative to the everyday on-the-job precautions and practices regarding bird and bat roosts? Certainly when it comes to our health, it makes most sense to be conservative and err on the side of safety, even in the cases of minor infestations of birds and bats. When inspecting attics that contain any bird or bat feces, wear a respirator capable of filtering out particles down to 0.3 micron, such as a HEPA filter. Painters’ masks and ordinary pesticide cartridge respirators do not provide adequate protection.

Additionally, by wearing a HEPA filter respirator in areas where deer mice are prevalent, you also protect yourself against biohazards (such as hantavirus) that are associated with these mice. Wearing gloves and coveralls is also a good idea when working in these areas. If the attic contains only minor accumulations of bird or bat droppings, the droppings can be cleaned up with soap and water. Small amounts of droppings can be sealed in a plastic garbage bag and disposed of as ordinary trash. Removal and cleanup of large quantities of droppings, however, is not a job for most pest management professionals. These situations call for environmental engineers or specialists trained in dealing with potential biohazardous wastes and their removal.

ADDITIONAL UPDATES. To obtain a complete copy of the 22-page booklet “Histoplasmosis: Protecting Workers at Risk,” contact the National Institute for Occupational Safety and Health, Publications Dissemination, 4674 Columbia Parkway, Cincinnati OH 45226-1998. The book provides outstanding detailed information and is worth having in your “biohazards file” for the office.

You can also access their website and obtain the information online at www.cdc.gov/ncidod/dbmd/fungal.htm. While here, you have access to information on histoplasmosis as well as information about any other infectious disease that should be of concern to the pest control industry, such as rabies, hantavirus and plague. Without doubt, it is one of the most comprehensive sites on the web.

For quick answers to questions regarding worker health and safety precautions during disturbances of soil, bat droppings or bird manure that might be contaminated with H. capsulatum spores, call NIOSH at 800/356-4674.

Dr. Robert Corrigan, a contributing editor to PCT magazine, is president of RMC Pest Management Consulting, 5114 Turner Road, Richmond IN 47374, 317/939-2829.