It was originally used against microsporidian parasites Nosema apis infections in honey bees.
Some studies found it to be effective against some myxozoan parasites, including Myxobolus cerebralis, an important parasite of fish; however, in the more rigorous tests required for U.S. Food and Drug Administration approval, it was ineffective.
There are reports that fumagillin controls Nosema ceranae, which has recently been hypothesized as a possible cause of colony collapse disorder.
The latest report, however, has shown it to be ineffective against N. ceranae.
Fumagillin is also investigated as an inhibitor of malaria parasite growth.