I do hope someone can correct me if I am wrong-- I have studied a lot of avian biology, but I am not an expert nor a veterinarian trained in avian medicine.
I understand that fipronil distributes in the oil glands of mammals. Mammals (at least the one that Frontline is intended for) have oil glands throughout their skin, as do we. Thus, the distribution of fipronil in the skin makes sense for mammals. Birds, however, do not have oil glands that translate to those of a mammal; most birds (or, in this case let us just assume chickens) have a singular oil gland, the 'preen' gland or more scientifically the uropygial gland at the base of the tail. This gland excretes the oils/wax esters that the bird then uses its beak and face to distribute over the feathers of the entire body. Because of the method of distribution, birds often ingest a fair bit of the preen oil, in addition to get it on the skin of the face (especially around the eyes and cheeks).
Because of this, my questions are:
1. Does fipronil actually distribute itself solely to oil glands in the skin, and if so does it do so in a chicken? Does it concentrate in the uropygial gland?
2. If the above is true, does this mean that when preening, the chicken ingests more fipronil than we expect, and can possibly cause short or long term health problems in the chicken or the people that eat the chicken's products?