In trying to find answers to the question, we consulted two documents: 1) Bats: Information for Wisconsin Homeowners by Scott Craven and Frank Iwen and 2) Histoplasmosis: Protecting Workers at Risk by the US Dept of Health and Human Services, CDC. DOH also spoke with Jim Kazmierczak in the Communicable Disease Section of our Bureau.
The bat droppings, particularly when they are so thick, are likely to be contaminated with a fungus, Histoplasma capsulatum. As long as people are not in contact with fugal spores, they are unlikely to be affected by them. However, when people inhale spores from the fungus, they may become ill with a disease known as histoplasmosis. Symptoms of hystoplasmosis include some combination of mild, flu-like respiratory illness, a general ill feeling, chest pain, fever, cough, headache, loss of appetite, shortness of breath, joint and muscle pains, chills, and hoarseness. Although there are other, more rare illnesses associated with exposure, the most likely is histoplasmosis.
In warm, moist conditions with lots of organic material (bat droppings), mold growth may be stimulated. When mold spores are released into the air, affected people may experience increases in asthma attacks.
The mites the exterminator saw may include members of several species that are able to live away from a warm blooded animal. Although their bite is not particularly harmful, if they come in contact with skin, the person may experience an allergic reaction and develop a skin rash in response.
Contact with blood, urine, or manure of rabid bats is not a risk factor for rabies.
Other health concerns are related to the removal and disposal of bat wastes. Workers need to be protected, dust must be controlled so that it does not enter the air of the living space, and special permission may be needed to dispose of the "bio-hazard" in a landfill.