The filarioidea are a family of parasitic worms. In addition to their biological similarities, they all have hosts that are vertebrates that spend at least some of their life cycle out of water. The most commonly family of vertebrates affected are birds. In addition, they all have an intermediate stage in an arthropod (a hard shelled invertebrate). Six of them cause diseases in humans and share a similar life cycle and symptoms. Three others also infect humans, but rarely cause any symptoms. They are also all susceptible to the same group of anti-parasite medications.
The relationship between these parasites and certain diseases has been well known since ancient times. The earliest references in ancient literature already treat these diseases as well identified and fairly common.