116 



PARASITES OF THE DOMESTIC ANIMALS 



Follicular Mange of the Dog. — Demodectic mange, or the so-called 

 red mange of dogs, is of frequent and world-wide occurrence. The 

 lanciform mites enter the orifice of the hair follicle where they multiply 

 and occupy the follicle and sebaceous gland in large numbers, lying 

 closely pressed together and almost invariably with the niouth parts 

 directed toward the bottom of the foUicle (Fig. 70). In this location 

 they may be found in all stages of development, from eggs to sexually 

 mature individuals and ovigerous females. As a result of this con- 

 stant increase there is a dilation of the hair follicle and gland, the pres- 

 sure and irritation producing degenerative 

 changes in the lining epithelium of the 

 follicle and hair papilla which causes the 

 hair bulb to become loosened from its 

 attachment. 



Symptoms and Course. — The degree of 

 irritation and extension of the inflamma- 

 tory process to the surrounding tissue will 

 be influenced by the number and activity 

 of the mites. There may be no more man- 

 ifestation of their presence than a hyper- 

 secretion of sebaceous material. Where, on 

 the other hand, these causative factors are 

 sufficient to produce an acute inflammation 

 involving the surrounding derma, there 

 will be a dilation of the contained blood 

 vessels with increased formation of epi- 

 dermic cells. Increased desquamation of 

 the surface cells follows, and later there is 

 an invasion of pyogenic organisms into the 

 inflamed and dilated follicles, resulting in 

 the formation of pustules and in some cases large abscesses. 



Though follicular mange, owing to its resistance to treatment and 

 general septic intoxication, frequently terminates in death, its course 

 at the commencement is very slow. In its early manifestations there are 

 merely somewhat reddened areas, usually of the skin about the eyes, 

 breast, elbows, or it may be at the toes. As the hairs fall away small 

 papules are observed, and the affected patches become covered with 

 fine, powder-like scales. The infection is extended by the mites aban- 

 doning the originally invaded follicles and entering the surrounding 

 healthy ones, the spreading being aided somewhat by the rubbing and 

 licking of the animal. As new parts are invaded the skin becomes de- 

 cidedly red and, especially about the cheeks and breast, thickened, 

 wrinkled, and crusty; the eyelids are swollen and covered at their borders 

 by a purulent discharge. 



m 



m 



Fig. 70. — Demodex folliculo- 

 rum: a, mite greatly enlarged; b, 

 mites in hair follicle and seba- 

 ceous gland — enlarged (after Os- 

 born, from Murry, Bui. No. 5, 

 Bureau of Entomology, U. S. 

 Dept. of Agr.). 



