External Parasites 



225 



to be composed of numerous mites and their debris. The 

 irritation of the mites often causes the birds to pull their 

 own feathers. Birds affected often pull each others' feathers. 

 Some of the so-called feather eating is due to the presence 

 of this parasite, but fowls sometimes pull each others' 

 feathers when the parasite is not present. Salmon says this 

 disease does not affect the general health of the bird and does 

 not appear to 

 disturb gain in 

 flesh or egg pro- 

 duction, but 

 Theobald says 

 that the disease 

 checks egg lay- 

 ing in hens and 

 affected cocks 

 become emaci- 

 ated and some- 

 times die. 



Etiology. — The 

 mite Sarcoptes 

 las vis which 

 causes this dis- 

 ease is smaller than the one which causes scaly leg. They 

 live at the base of the feathers in the epidermal debris 

 referred to above. A flock becomes infested by the intro- 

 duction of one or more birds carrying the mites. The mites 

 are spread from bird to bird by the male in copulation. The 

 distribution is often very rapid so that the whole flock is 

 soon affected. 



Treatment. — The disease should be prevented by taking 

 care not to introduce infested birds. If it appears, all affected 

 birds should at once be isolated. The mites yield easily to 

 treatment. The infested areas may be rubbed with some 



Q 



Fig. 46. — Egg containing female Sarcoptes Icevis 

 var. gallince. (After Theobald.) 



