[Bird Control] Bird Droppings and Public Health

Not only are bird droppings an unsightly mess that can be difficult to remove and cause slip-and-fall accidents, they also harbor numerous human pathogens. Just how dangerous are bird droppings to human health? The question seems simple but quantifying a human’s risk of acquiring disease from a bird or its droppings is difficult since exposure to the pathogens does not always result in disease and most bird-related zoonotic diseases are not reportable to health authorities.

One way to understand the risk bird droppings pose to human health is to look at how common diseases can be transmitted through contact with bird droppings. Histoplasmosis and cryptococcosis are two fungal diseases that can be acquired through inhalation of infected bird feces, while gastroenteritis (vomiting and diarrhea) can be caused by accidental consumption of a variety of different bacteria found in bird feces. Bird control specialists are considered to have an increased risk of acquiring these illnesses due to their chronic exposure to the pathogens present in fresh and dried bird droppings.

Most people exposed to the fungus that causes histoplasmosis (Histoplasma capsulatum) do not get ill, however some may develop respiratory signs (cough, fever, chest pains) that can cause serious lung disease and even death if untreated. H. capsulatum thrives in older bird roosts containing dried bird droppings that are in contact with the soil, as well as in old bird droppings from roosts established three years or more. Outbreaks (multiple cases acquired from a similar location) resulting from untrained workers removing dried bird droppings in a way that aerosolize fungal spores so they can be inhaled into the lungs and cause human illness are well-documented in medical literature, as are cases caused by building demolition.

WHO’S AT FAULT? According to a Center for Disease Control and Prevention report on histoplasmosis, demolition workers, bridge inspectors, chimney cleaners, maintenance staff, microbiology laboratory workers, farmers, roofers, spelunkers and gardeners all have removed bird droppings in a way that resulted in human illnesses. A particularly large outbreak of the disease occurred in 2001 when 523 high school students became ill after soil in their school’s courtyard containing bird droppings was rototilled by a maintenance worker. The largest outbreaks of histoplasmosis in the United States occurred in the late 1970s in Indiana, when over 120,000 people became ill, and 15 died, after a building containing bird droppings was demolished.

There are no reports of pest control specialists removing droppings in a way that resulted in histoplasmosis or human illness in general. This may reflect either under-recognition of infection since the majority of histoplasmosis cases are asymptomatic, or it may reflect the extensive training bird control specialists receive in handling bird dropping removal jobs. Nonetheless, bird control specialists should be aware of flu-like illnesses after exposure to bird droppings and inform medical professionals of their potential exposure.  

CRYPTOCOCCOSIS. Cryptococcosis also is caused by a fungus, Cryptococcus neoformans that thrives in fresh pigeon droppings. Spores of C. neoformans can be inhaled, initially causing a lung infection, often with no signs of disease, and eventually spreads to the brain, causing meningitis. Unlike histoplasmosis, the disease is rare in healthy individuals, but among immunocompromised persons, the prevalence of the disease has been recorded as high as 8 percent in New York City. Recent evidence suggests that the majority of human infections occur during childhood and manifest symptomatically later in life.

In some areas of the United States, cryptococcosis spores are found in 84 percent of bird dropping samples taken from older, well established roosts. Unlike histoplasmosis, outbreaks of cryptococcosis have not been documented. There are no reports of cryptococcosis infections in pest control specialists. Cryptococcal meningitis is difficult to diagnosis, and bird control specialists should consider notifying their doctor if they suspect possible pathogen exposure.

A WATCHFUL EYE. Bird droppings can contaminate municipal water sources and food, causing outbreaks of gastroenteritis due to bacterial species such as Camplobacter, Salmonella and fecal coliform organisms. The primary mode of transmission of these organisms to humans is through inadvertent eating of bird droppings containing the bacteria. Birds are not permitted in food-handling areas of retail food-handling facilities because of the potential of food contamination by bird feces. In some local health jurisdictions, the presence of a single bird in a food-handling area necessitates immediate closure of the facility until the bird is removed. Persons working with populations of birds and bird droppings must practice good hand washing to prevent hand to mouth contact with the droppings from occurring.

Large populations of roosting birds produce large amounts of droppings. Bird control specialists are well aware of the amount of droppings that can accumulate. A U.S. Army report outlining a detailed protocol for bird and bat excrement removal recommends that a pre-placement evaluation should be performed on all those who clean up bird and bat excrement. Employees should be screened for general health status and any conditions that may predispose them to infection by fungi. Anyone with a weakened immune system, such as persons with AIDS, those with cancer and receiving chemotherapy, and those on high-dose, long-term steroid therapy or other immunosuppressive drugs should not work around bird droppings. The best way to protect oneself from inhalation of fungal spores while cleaning bird droppings is to wear proper respiratory protection, carefully wet droppings prior to removal and limit exposure to enclosed areas with bird droppings.

CONCLUSION. Bird dropping removal can cause human illness. It is important that pest control specialists realize that there are risks of disease associated with bird dropping removal, the symptoms of common illnesses associated with bird droppings, and ways to reduce their risk from acquiring these illnesses. 

References
Histoplasmosis: Protecting Workers at Risk. 2004. U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, National center for Infectious Disease DHHS (NIOSH) Publication Number 97-146

Managing Health Hazards Associated with Bird and Bat Excrement. 1992. U.S. Army Center for Health Promotion and Preventive medicine USAEHA TG No. 142

The author is an associate public health biologist with the Vector-Borne Disease Section of the California Department of Health Services.

Reducing Risk to Others During Bird Dropping Clean-up Jobs

Although there are no documented cases of bird control specialists causing outbreaks of histoplasmosis, cryptococcocis or gastroenteritis, other professions such as maintenance workers, bridge painters and farmers have cleaned bird droppings in a way that resulted in significant human cases. Here are a few things to keep in mind while cleaning up bird droppings:

• All droppings should be considered infectious.
• Always wear disposable protective clothing, shoe coverings, respirator protection capable of excluding particles of 0.3 micron size or a supplied air respirator with full face piece, and gloves. Dispose of all protective clothing in plastic bags.
• Saturate the droppings with water or other approved liquid prior to removing them to prevent debris and pathogens from becoming airborne. The use of high-pressure hoses may scatter droppings before they are appropriately wetted.
• Do not perform bird excrement removal in public buildings during normal working hours. When possible, schedule the removal for weekends or other periods of minimal building use. All heating and cooling system air intakes should be closed during cleanup.  
• Provide signage and barricades during the clean up to exclude the public.
• Dispose of droppings and associated soil in 3 millimeter or thicker plastic bags and transport them to a landfill immediately.

Symptoms of the Most Common Bird-borne Diseases

Histoplasmosis

• Causative agent: Histoplasma capsulatum, a dimorphic fungus
• Source: Primarily soil enriched with bird or bat droppings 
• Mode of Infection: Inhalation of spores 
• Symptoms: Most infections have no symptoms or present as a mild influenza like illness. Common symptoms are cough, fever, weakness, body pain, chills and chest pain. In chronic infections, pneumonia, blindness, and even death are possible.

Cryptococcosis

• Causative agent: Cryptococcus neoformans
• Source: Dust contaminated with pigeon or bat droppings
• Mode of Infection: Inhalation
• Symptoms: The initial infection may not have symptoms, but if the infection moves to the central nervous system, meningitis may result and may be difficult to diagnose. Left untreated the meningitis can be fatal.

Gastroenteritis

• Causative agents: Camplobacter, Salmonella, fecal coliform bacteria such as Escherichia coli.
• Source: Fresh bird droppings
• Mode of Infection: Ingestion of bird droppings
• Symptoms: Diarrhea, stomach cramps, vomiting