Alexandria, I've always believed the idea of bloodfly "Nest Keepers" to be legend, or drunken miner talk, even though members of the Grand Guard have reported putting down "belligerent occupants" when burning out bloodfly infestations.
As such, this silvergraph represents a rare sighting. We can only conclude that the final stages of Bloodfly Fever occasionally result in an extraordinary kind of brain damage, wherein the host fixates on protecting the nests. The bloodflies in turn, welcome the afflicted person, and thus a symbiotic relationship results.
Bloodfly research never ceases to amaze. If we could procure a sample from the brain of one of these nest keepers, I'd love to observe the effects on rats or wolfhounds in my laboratory.