Humans have been living in close proximity to bats for many years, and no one has ever proven a link between bats and human illnesses.
Our personal experience is that bat guano is safe. We have been harvesting hundreds of tons of bat guano from caves in Indonesia for more than ten years and none of our 100-plus employees at our factories have ever gotten sick from exposure to bat guano. There are additional hundreds more villagers who scoop raw guano from inside caves and we have never heard of any of them becoming sick.
Bat guano was used extensively as a fertilizer in North America and Europe from the 1840’s until the development of the Haber-Bosch process in Germany in the early 1900’s. Bat guano was harvested and used by the shiploads, harvested mainly from the west coast of South America and Pacific Islands. No one was ever reported to have fallen sick from the harvesting or use of bat guano in the 1800’s. Today, bat guano is used extensively as an organic fertilizer by craft growers, and is mixed into hundreds of thousands of yards of potting and planting soil mixes without a single report of illness caused.