People who work in certain jobs are at risk for histoplasmosis. Histoplasmosis is an infection caused by Histoplasma, a fungus that lives in the soil. Anyone who works with or near material contaminated with the fungus can develop histoplasmosis. Most people who breathe in the fungus never have symptoms, but some people can develop severe histoplasmosis and get very sick. Employers and workers can take steps to prevent histoplasmosis in the workplace.

Certain job tasks can put workers at risk

Certain activities have risks for exposure to the fungus that causes histoplasmosis:

• Disturbance of large accumulations of bird or bat droppings (scraping droppings from a bridge; shoveling droppings from a building or other structure; cleaning a chicken coop)
• Soil disruption (digging or excavation)
• Plant matter disruption (handling trees or landscaping)
• Demolition, construction, or renovation
• Working in caves

In the United States, the fungus that causes histoplasmosis mainly lives in the central and eastern states, particularly areas around the Ohio and Mississippi River Valleys. Some people in areas where Histoplasma is common may have a higher chance of getting histoplasmosis, including people who work in:

• Construction and demolition
• Mining, quarrying, and oil and gas extraction
• Agriculture and forestry industries

Prevent histoplasmosis in the workplace

The best way to prevent exposure to the fungus that causes histoplasmosis is to prevent the accumulation of bird or bat droppings in the first place. This can be accomplished by excluding bats and birds from buildings. In some cases, large amounts of bird or bat droppings should be cleaned up by a professional company that specializes in handling hazardous waste.

Employers can help keep workers safe during high-risk activities

If workers must remove bat or bird droppings, or if construction, excavation, or demolition must be done in areas where Histoplasma is common, employers should:

• Develop a site safety plan to minimize workplace exposures. The plan should have input from management, employee representatives, and health and safety professionals.
• Reduce or eliminate dust. Spray water or use other dust suppression techniques.
• Dispose of any material that might be contaminated with Histoplasma safely while following state and local requirements.
• Post health risk warnings in areas known or suspected to be contaminated with Histoplasma.
• Train workers so they understand the potential risks and how to protect themselves.
• Provide personal protective equipment (PPE) and associated training to workers.
• Encourage workers with workplace exposures to Histoplasma or symptoms of histoplasmosis to seek a medical evaluation with a healthcare provider.

Workers can take steps to protect themselves

Workers should try to eliminate or reduce dust and can use PPE to protect themselves from exposures to Histoplasma. Disposable protective clothing and shoe coverings can help prevent spreading the fungus to other places like a worker’s car or home. Workers should talk to a crew leader or supervisor about selecting the appropriate PPE.

Workers who may have been exposed to Histoplasma at work or have symptoms of histoplasmosis should:

• Talk to a crew leader or supervisor and their Occupational Health or Risk Management Department
• Contact the local city, county, or state health department if their workplace does not have the above services
• See a healthcare provider for medical care
• Ask a healthcare provider about testing for histoplasmosis

Histoplasmosis is an infection caused by a fungus called Histoplasma. The fungus lives in the environment, particularly in soil that contains large amounts of bird or bat droppings. People can get histoplasmosis after breathing in the microscopic fungal spores (also known as conidia) from the air. Although most people who breathe in the spores don’t get sick, those who do may have a fever, cough, and fatigue. Many people who get histoplasmosis will get better on their own without medication. In some people, the infection can become severe and spread from the lungs to other parts of the body such as the eyes and the lymph nodes. This is more common in people with weakened immune systems or other medical conditions.

Areas where Histoplasma lives

Histoplasma, the fungus that causes histoplasmosis, lives throughout the world, but it’s most common in North America and Central America. In the United States, Histoplasma mainly lives in soil in the central and eastern states, particularly areas around the Ohio and Mississippi River Valleys, but it can likely live in other parts of the country as well, especially if the environmental conditions are highly suitable. In the environment, Histoplasma is undetectable to the naked eye. Learn more about the approximate areas with Histoplasma.

Histoplasma grows well in large amounts of bird or bat droppings

Histoplasma grows especially well in soil or other environmental material containing large amounts of bird or bat droppings. Bird and bat droppings act as a source for the growth of Histoplasma already present in soil.Fresh bird droppings on surfaces such as sidewalks and windowsills likely does not pose a risk for histoplasmosis because birds themselves are rarely infected with Histoplasma. Unlike birds, bats can become infected with Histoplasma and may be able to excrete it in their droppings.

A large number of birds or bats, even without obvious accumulations of droppings, can also pose a risk for Histoplasma exposure. The types of birds typically associated with histoplasmosis outbreaks include chickens, blackbirds (starlings and grackles), pigeons, and gulls. Presence of birds, bats, or large accumulations of their droppings is not required for Histoplasma to grow, and many patients with histoplasmosis do not have such exposures.

Histoplasma has been detected in some organic fertilizers in Latin America, but more studies are needed to understand whether the fungus can survive commercial fertilizer manufacturing processes.

Environmental testing for Histoplasma

Detecting Histoplasma in environmental samples can be challenging. Routine environmental sampling for Histoplasma is not recommended, although research is needed to evaluate potential targeted testing strategies. Focused polymerase chain reaction (PCR) or culture testing can help confirm a suspected environmental source during a histoplasmosis outbreak. In outbreak settings without a clear exposure, large-scale environmental testing is unlikely to be useful. In outbreak settings with a very clear exposure, environmental testing may not be necessary, particularly if the results would not change public health recommendations to prevent future cases. Also, an environmental sample that tests negative for Histoplasma does not necessarily mean that the fungus is not present or was not present at the time the exposure occurred.

For any accumulations of bird or bat droppings, soil, or other environmental material suspected to be contaminated with Histoplasma, the safest approach is to assume the material is contaminated, take exposure precautions, and remediate it accordingly.

Anyone who works with or near material contaminated with Histoplasma can develop histoplasmosis. Most people exposed to Histoplasma never have symptoms. For people who do get sick, the severity of histoplasmosis varies widely. The severity depends on the amount and length of the exposure and whether the person has other conditions that might put them at higher risk for developing the severe forms of histoplasmosis. Symptoms of histoplasmosis usually appear between 3 and 17 days after a person breathes in the fungal spores.

Activities associated with histoplasmosis

Environmental disruption of Histoplasma habitats is often a key factor associated with histoplasmosis outbreaks and with isolated cases, although to a lesser extent. These activities include:

• Disturbance of large accumulations of bird or bat droppings (scraping droppings from a bridge; shoveling droppings from a building or other structure; cleaning a chicken coop)
• Soil disruption (digging or excavation)
• Plant matter disruption (handling trees or landscaping)
• Demolition, construction, or renovation
• Working in caves

Jobs associated with histoplasmosis

In areas where Histoplasma is common, people who work in construction, demolition, and extraction occupations and in agriculture and forestry industries may be at higher risk for histoplasmosis. People who work in other occupations or industries and are exposed to bird or bat droppings or are involved with activities that disrupt the environment are also at risk.

Most of what we know about specific jobs that may be related to a higher chance of getting sick with histoplasmosis comes from outbreak investigations. Approximately one-third of histoplasmosis outbreaks in the United States are work-related. However, outbreak-related histoplasmosis cases represent only a small fraction of overall known cases (about 5%). Examples of people affected by work-related histoplasmosis outbreaks include:

• Bridge workers
• Construction or demolition workers
• Farmers
• Landscapers or tree removal workers
• Microbiology laboratory workers

Histoplasmosis outbreaks have also affected people who were exposed in the workplace but not directly involved in activities that initiated the outbreak (for example, outbreaks affecting office building workers after construction or renovation).

Occupational health and safety specialists use the hierarchy of controls [Figure 1] to determine how to implement feasible and effective control solutions to occupational hazards. This framework can be used to prevent exposure to histoplasmosis in the workplace. Elimination (removing the hazard) and substitution (replacing the hazard) are the most effective ways to reduce occupational hazards but can be difficult to implement for infectious agents such as Histoplasma. In some cases, large amounts of bird or bat droppings should be cleaned up by a professional company that specializes in handling hazardous waste.

Development of a site safety plan

Developing a site-specific safety and health plan is an important step in minimizing workplace exposures. The plan should have input from management, employee representatives, and health and safety professionals. A comprehensive plan includes the identification of potential hazards and a description of the necessary measures to prevent, control, and reduce those hazards. Measures should include engineering and administrative controls and use of PPE.

A. Elimination and engineering controls

Excluding bats or birds from a building

Because work-related histoplasmosis often involves disruption of bird or bat droppings, the best way to prevent exposure to Histoplasma is to prevent the accumulation of bird or bat droppings in the first place.

To move bats away from an occupied roost in a building:

• Identify and seal entry and exit points. Seal even the smallest holes because some types of bats can squeeze through an opening as small as a dime.
• Install and maintain lights in the roosting area. This will force bats to seek another daytime roosting site.
• Construct bat houses near former roosts. This is a common practice for the welfare of evicted bats and may also keep the bats from colonizing in nearby buildings.

Ultrasonic devices and chemical repellents are not effective for eliminating bats from a roosting area.

To exclude birds from a building:

• Identify and seal entry and exit points.
• Consider visual deterrents (balloons, flags, lights, and replicas of hawks and owls) and noises, which may scare birds away but may not have long-lasting effects.
• Use nontoxic, chemical bird repellents like liquids, aerosols, and nondrying films. Disadvantages of these materials are that some are messy, and none are permanent. Even the most effective ones require periodic reapplication.
• Use mechanical anti-roosting systems consisting of angled and porcupine wires made of stainless steel. These systems may require some occasional maintenance to clear nesting material or other debris from the wires.

Controlling dust generation when removing bat or bird droppings

Once a roosting site has been discovered in a building or other location, make plans to restrict the area and determine the extent of contamination. When deciding about removing accumulations, consider factors like the amount and location of the material, the structural integrity or soundness of the building or structure, weather conditions, and whether people are near it. When an accumulation of bat or bird dropping is discovered, removing the material may not always be the next step. Simply leaving the material alone may be the best course of “action” if human activity around the location is unlikely.

If the material must be removed, work practices and dust control measures that eliminate or reduce dust generation will lower risk of infection. For example, carefully spraying dry, dusty material with water instead of shoveling or sweeping it, can reduce the amount of aerosolized material (or material dispersed or spread into the air). Adding a surfactant (also called a wetting agent, like a detergent) to the water might reduce further the amount of aerosolized material. Once the material is wetted, it can be collected in a secure container for immediate disposal. An alternative method is to use an industrial vacuum cleaner with a high-efficiency filter to collect potentially contaminated material. Truck-mounted or trailer-mounted vacuum systems are recommended for areas with large accumulations of bat or bird manure. See the personal protective equipment section for workers involved in these activities.

In most cases, environmental sampling to confirm Histoplasma is no longer present after removal of bird or bat droppings is unnecessary. However, before a removal activity is considered finished, the cleaned area should be visually inspected to ensure no residual dust or debris remains.

Disinfecting potentially contaminated material

Disinfectants have occasionally been used to treat contaminated soil and accumulations of bat droppings when removal was not practical or as a precaution before a removal process was started. However, there are no Environmental Protection Agency-approved products registered specifically as soil disinfectants or as being effective against Histoplasma. In past histoplasmosis outbreak settings, formaldehyde was used to decontaminate material contaminated with Histoplasma. This is not recommended because formaldehyde can cause a variety of health problems.

Disposing of waste

Any material removed from a work site that might be contaminated with Histoplasma should be disposed of properly and safely and should not be moved to another area where it could still be a health hazard. State and local requirements for the removal, transportation, and disposal of potentially contaminated material should be followed. If state or local landfill regulations define material contaminated with Histoplasma to be infectious waste, incineration or another disposal method may also be required. If disposing in a landfill, arrangements should be made with a landfill operator.

Controlling aerosolized dust during construction, excavation, and demolition

Even in the absence of large accumulations of bat and bird droppings, Histoplasma spores can be aerosolized (or dispersed or spread into the air) during construction, excavation, or demolition. Once airborne, spores can be carried easily by wind currents over long distances, and these spores could infect people outside of the work site. Regardless of whether a work site is in an area where Histoplasma is common, take precautions to prevent dust aerosolization from active and inactive bird or bat roosts.

Water sprays or other dust suppression techniques should be used to reduce the amount of dust aerosolized during construction, excavation, or demolition in regions where Histoplasma is common. During windy periods or other times when typical dust suppression techniques are ineffective, earthmoving activities should be interrupted. All earthmoving equipment (bulldozers, trucks, and front-end loaders) should have enclosed cabs with air-conditioning and HEPA filtration (if available) to protect their operators. Air filters on air-conditioners should be inspected on a regular schedule and cleaned or replaced as needed. During filter cleaning or replacement of exceptionally dusty air filters, maintenance workers should wear respiratory protection if there is a potential for the dust to be aerosolized. Truck beds carrying dirt or debris from a work site should be covered, and all trucks should pass through a wash station before leaving the site. When at a dump site, a truck operator should ensure that people in the vicinity will not be exposed to aerosolized dust while the truck is emptied.

B. Administrative controls

Posting health risk warnings

Areas known or suspected to be contaminated with Histoplasma, like bird or bat roosts, attics, or entire buildings that contain accumulations of bat or bird droppings, should be posted with signs to warn people of the health risk. Each sign should provide the name and telephone number of a person to contact with questions about the area. In some situations, fences or locks may be needed to prevent people from entering.

Hazard communication and training

Before starting an activity that could disturb any material that might be contaminated by Histoplasma, workers should understand the potential risks and how to protect themselves. Employers should inform and train workers on potential work hazards and associated safe practices, procedures, and protective measures. A written hazard communication program about histoplasmosis should include:

• What histoplasmosis is and what causes it
• Signs and symptoms of histoplasmosis
• Treatment for histoplasmosis
• Who can get histoplasmosis
• Risk factors for developing symptomatic histoplasmosis
• Where Histoplasma lives
• Jobs and activities with risks for Histoplasma exposure
• How to prevent Histoplasma exposure

C. Personal protective equipment

In addition to elimination, engineering and administrative controls, personal protective equipment (PPE) including respirators can be used to protect workers from exposures to Histoplasma.

Respiratory protection

There are no occupational exposure limits for Histoplasma. Respirators are designed to reduce the concentrations of dust and harmful airborne pathogens in the wearer’s breathing air. Respirators are generally divided into two main categories: air-purifying respirators (filter contaminated air) and atmosphere-supplying respirators (provide an alternative supply of breathable air). Workers needing protection against Histoplasma should use particulate-filtering air-purifying respirators (Figure 1). These include:

• Filtering facepiece respirators (e.g., N95)
• Elastomeric respirators (half facepiece or full facepiece)
• Powered air-purifying respirators (PAPRs) (tight fitting and loose fitting)

Respirators must be NIOSH-approved and properly selected and used. If the filters become damaged or the respirator becomes difficult to breathe through or, in the case of a PAPR, the airflow falls below the minimum level, the worker should immediately move to a non-contaminated area and replace the filter. Failure to do so might defeat the protective role of the respirator.

Research is limited on the effectiveness of respirators in protecting workers from breathing in dust and Histoplasma. However, respirators are expected to offer some level of protection since the diameter of Histoplasma spores ranges from 1 µm to 5µm. NIOSH-approved respirators will collect all types of workplace aerosols, including airborne infectious organisms with very high efficiency.

Respirators must be selected based on:

• The level of risk for histoplasmosis while performing the job
• The required assigned protection factor (APF; the level of workplace protection that each class of respirators is expected to provide to employees when the employer implements a continuing, effective respiratory protection program) needed to reduce the level of risk to an acceptable level OSHA assigned protection factors are found in Table 1 of the OSHA Respiratory Protection Standard.
• The advantages and disadvantages of each respirator class

In areas where Histoplasma is common,

Consider use of half-facepiece respirators, including filtering facepiece respirators, during medium risk activities like:

• Working outdoors, particularly involving soil or plant matter disruption (demolition, excavation, farming)
• Working with live poultry or other birds (except where large accumulations of droppings exist, which pose a higher risk)

Consider use of a loose-fitting or tight-fitting PAPR equipped with any of the approved filters (HE, PAPR100-N, and PAPR100-P) or a full facepiece with 100 series filters to be worn before and throughout high-risk activities like:

• Remediating sites with documented Histoplasma or those linked to human illnesses
• Disrupting or cleaning up large accumulations of bird or bat droppings
• Removing trees or other plant material at large bird roosting sites
• Entering caves or tunnels where bats live when there is a possibility of disrupting bat droppings

If PAPRs and full facepiece respirators with 100 series filters are not available, consider using filtering facepiece respirators. It should be noted that filtering facepiece respirators only have an assigned protection factor of 10 so they only provide 20% of the protection afforded by PAPRs (APF 25–50) and full facepiece APRs (APF 50). A filtering facepiece respirator will provide some protection. The respiratory protection program manager will need to determine whether this is enough protection depending upon the wearer’s environment.

OSHA requires employers to develop and implement a written respiratory protection program with required worksite-specific procedures and elements for required respirator use (29 CFR 1910.134). The program establishes that the employee required to wear a respirator must be trained, medically evaluated, and fit tested, among other program requirements. Cleaning, disinfecting, and properly storing a respirator are also important to guarantee they protect the wearer efficiently.

Other recommended PPE

Gloves should be worn when removing large amounts of droppings or when a person’s hands will touch contaminated soil or other material. Disposable gloves (vinyl, nitrile, PVC, or polyethylene) should be worn under regular cotton or leather work gloves. The use of eye protection (either eyecup or cover-type safety goggles) is recommended, especially when working in ventilated worksites.

Disposable protective clothing and shoe or boot coverings should be worn whenever regular work clothing and shoes might be contaminated with dust containing Histoplasma spores. This can reduce or eliminate the likelihood of transferring spores to places away from a work site, like a car or home. When spore-contaminated material is likely to fall from overhead, workers should wear disposable protective clothing (coveralls) with hoods. Workers should wear disposable shoe coverings with ridged soles made of slip-resistant material to reduce the likelihood of slipping on wet or dusty surfaces. Since protective clothing can be more insulating than regular work clothing, precautions may need to be taken to control heat stress. After completion of work, workers should remove all protective clothing and shoe coverings and seal them in heavy duty plastic bags for disposal.

What to do if you are exposed at your workplace

If you think you’ve been exposed to Histoplasma at work, you should contact your crew leader or supervisor and your occupational health or risk management department. If your workplace does not have these services, you should contact your local city, county, or state health department. We do not know if antifungal medication (prophylaxis) can prevent people from getting sick with histoplasmosis after a workplace exposure to Histoplasma but it can be considered for high-risk exposures. For more information about laboratory exposures to Histoplasma, please see Guidance for laboratory workers who handle Histoplasma.

What to do if you are sick

If you think you have histoplasmosis after working in an area where Histoplasma is common, report your symptoms to your crew leader or supervisor and visit a healthcare provider, if needed. Tell your healthcare provider that you work in an area where Histoplasma is common and ask to be tested for histoplasmosis.

In addition to Histoplasma, Cryptococcus neoformans may also be a health risk for workers who disturb accumulations of bird or bat droppings. Other concerns include rabies virus for workers who handle dead bats and Chlamydia psittaci for workers who work in environments of certain birds.

Cryptococcosis

Cryptococcus neoformans is a causative agent of the fungal infection cryptococcosis. C. neoformans lives in the environment throughout the world. Its specific habitats include soil, decaying wood, tree hollows, or bird droppings. People can become infected with C. neoformans after breathing in the microscopic fungus, although most people exposed to the fungus never get sick from it. Cryptococcosis often presents as meningitis or meningoencephalitis, with symptoms including headache, fever, neck pain, and sensitivity to light. Infection may also develop in the lungs, causing cough, chest pain, or shortness of breath.

C. neoformans infections are rare in otherwise healthy people. Most cases occur in people who have weakened immune systems, particularly those who have advanced HIV/AIDS.

Occupational considerations

Avoiding C. neoformans is generally difficult because it is common in the environment. Outdoor occupations, like landscaping and outdoor construction, have been associated with increased risk of cryptococcosis. Little is known about the specific activities that may increase risk of C. neoformans infection, although working near bird droppings may increase exposure. Healthcare providers should be aware of the increased risk of cryptococcosis in outdoor workers and consider this disease in patients with unexplained lung disease, lung nodules, or meningitis, even in patients without known weakened immune systems.

Rabies

Rabies is a fatal but preventable viral disease. It can spread to people and pets if they are bitten or scratched by a rabid animal. In the United States, rabies is mostly found in wild animals like bats, raccoons, skunks, and foxes. However, in many other countries dogs still carry rabies, and most rabies deaths in people around the world are caused by dog bites.

The rabies virus infects the central nervous system and can lead to death. There is often discomfort or a prickling or itching sensation at the site of the bite prior to fever and vague symptoms before progressing within days to acute symptoms of cerebral dysfunction, anxiety, confusion, and agitation. As the disease progresses, the person can experience delirium, abnormal behavior, hallucinations, hydrophobia (fear of water), and insomnia.

Occupational considerations

Workers who have the following exposures are at risk of rabies:

• Bite from a rabies-infected animal or human
• Contamination of an open wound, scratch, or abrasion with rabies-infected saliva or other rabies-infected tissue (neural tissue)
• Work in a laboratory where rabies virus is aerosolized or where workers may be exposed via needlesticks or other accidents
• Frequent entry into caves where bats are present

Workers who encounter a dead bat should never pick up the bat with bare hands. In the unlikely event the bat died from rabies, the rabies virus can remain in the carcass until decomposition is well-advanced and dry. Instead, whenever possible, use a shovel or other tool to pick up and move the dead bat. If the bat must be handled, heavy gloves should be worn to minimize risk of an accidental scratch or contamination of existing abrasions on the worker’s hands.

Rabies can also be prevented by vaccinating people at high-risk of infection before exposure occurs. These groups include:

• Workers at continuous or frequent risk of exposure to rabies virus (rabies research laboratory workers)
• Workers or other people who have exposures to rabies virus that might be recognized or unrecognized (veterinarians, those who regularly enter caves where bats and bat droppings are present)
• Workers or other people who have infrequent exposure to recognized sources of rabies (animal control workers working with animals that primarily live on the ground (terrestrial animals) where rabies is uncommon to rare)

If you do come into contact with a rabid animal or have a high-risk exposure, the efficacy of post-exposure prophylaxis approaches 100% when prompt medical care is provided. If you are bitten, scratched, or unsure whether a rabies virus exposure occurred, talk to a healthcare provider about whether you need post-exposure prophylaxis.

Psittacosis

Psittacosis is an infectious disease caused by the bacteria Chlamydia psittaci. The disease is most commonly associated with pneumonia caused by certain bacteria (atypical pneumonia), but the severity of illness can range from mild illness to serious, impacting multiple organ systems. Patients may develop mild illness with abrupt onset of fever, chills, headache, and muscle aches after an incubation period of 5–14 days. Dry cough is often present.

C. psittaci is transmitted to humans through inhalation of aerosolized dried droppings or respiratory secretions of infected birds such as psittacines (cockatiels, parakeets, parrots, and macaws), pigeons, or poultry. Transmission can also occur through direct contact with feathers, tissues, respiratory secretions of infected birds, or by mouth-to-beak contact.

Occupational considerations

Workers in occupations that involve contact with live birds or bird carcasses are at increased risk of infection. Such occupations include:

• Veterinarians
• Bird breeders
• Poultry workers
• Pet shop workers

Outbreaks have been described in turkey processing plants and chicken slaughter plants. An outbreak among English office workers was likely caused by indirect environmental exposure to infected pigeons.

The National Association of State Public Health Veterinarians published the Compendium of Measures to Control Chlamydia psittaci Infection Among Humans (Psittacosis) and Pet Birds (Avian Chlamydiosis), 2017, which provides recommendations to prevent transmission to humans. The recommendations to prevent occupational exposures to C. psittaci include quarantine procedures of newly-acquired birds or birds exposed to ill birds, cleaning and disinfecting cages, and other animal husbandry practices. Those handling ill birds or cleaning their cages should use appropriate personal protective equipment, including protective clothing, gloves, eye protection, and a disposable NIOSH-approved filtering facepiece respirator.