by overproduction of epidermal cells (acanthosis), resulting in a characteristic depilated and scaly appearance. Stress caused by the pruritus can be severe, and will result in 6% to 23% lost productivity of commercially reared pigs. Camels are prone to severe infestation with Sarcoptes. Feather mites The irritation caused to birds and poultry can cause loss of condition and production. Megninia ginglymura feeding at the base of feathers of poultry causes a pruritic dermatitis that irritates the birds and induces them to pull their feathers. The stress of the infestation can cause a 20% loss in egg production. Mites found in deeper layers of skin or within other organs Demodecosis Demodecosis in cattle caused by Demodex bovis can occur as dense, localized infestations with inflammation of the epidermis in hair follicles. This leads to pustular folliculitis and indurated (thickened) plaques within the skin. On cattle, these localized foci of infestation can become so large as to be clearly visible externally. The value of the hides from cattle infested this way is reduced. Pigs may be similarly affected by infestations with Demodex. Lung mites and mites of other tissues The mites of the Cytoditidae and Laminosioptidae invade the respiratory system, and then other tissues, of their hosts. Cytodites nudus infests poultry worldwide; although slight infestations cause little clinical harm, when infestation becomes heavy in individual birds, they can be severely weakened or die. Laminosioptes cysticola infests poultry where it accumulates in nodules that occur in the facia of subcutaneous muscle and also in the lungs. This causes little clinical harm to the birds, but devalues their meat intended for human consumption. Blood feeding Larvae of trombiculids cause severe pruritus to their hosts after they detach. The larva secretes a proteinaceous feeding tube, the stylostome, into the host's skin. This remains after the larva has completed engorgement on blood and induces an intense localized inflammation. Eutrombicula alfreddugesi and E. splendens are common in the Americas where they infest the skin of the face, muzzle, legs, and belly of cattle and horses. (Trombiculid mites also leave intensely pruritic spots on dogs and humans after feeding and such infestation is closely associated with the grassland and scrub habitats of the nonparasitic stages of the lifecycle.) Dense infestations of a poultry house by Dermanyssus gallinae lead to biting stress and loss of production of the birds (also humans working in the poultry houses are bitten). Originally