14 



CIRCULAR 338, U. S. DEPT. OF AGRICULTURE 



Figure 10.— The sucking louse of 

 dogs, Linognathus piliferus. Fe- 

 male. Ventral view. Enlarged. 

 From Neveu-Lemaire, 1912. 

 (Measurements: Male, 1.5 milli- 

 meters long; female, 2 millime- 

 ters long.) 



The sucking louse, Linognathus piliferus (synonym, Haematopinus 

 piliferus), is pale yellow, less than one twelfth of an inch Ions:, and has 

 a long, slender head (fig. 10), very different from the wide, blunt 

 head of the biting louse. It may appear blue after feeding on blood. 



The biting louse, Trichodeetes lotus (synonym, T. canis), is clear 

 yellow in color, with darker markings, smaller than the sucking louse, 

 and has a short, wide, blunt head (fig. 11). 



Cats are susceptible to attacks by the louse, Trichodeetes subros- 

 tratus, which is about the size of T. lotus of the dog, but has a more 

 pointed head. This is the only louse infesting cats; it is not common. 



Symptoms. — The sucking lice feed on se- 

 rum and blood, and the biting lice feed on 

 the scales, scurf, and superficial portions of the 

 skin. In either case they cause irritation, 

 which may be excessive in heavy infestations. 

 The itching due to their bites causes the in- 

 fested animal to scratch and rub, sometimes 

 causing sores in this manner, and constitutes 

 a drain on the nervous energy. Long-haired 

 dogs appear to be more susceptible to louse 

 infestation than short-haired dogs, and pups 

 and very old dogs are more susceptible to infestation and suffer 

 more from it than dogs of about mature age. The biting louse 

 shares with the flea the role of intermediate host of the common 

 double-pored tapeworm (p. 28), the louse becoming infested with the 

 intermediate stage of the tapeworm as a result of swallowing tape- 

 worm eggs as it feeds on the contaminated skin of the dog, and the 

 dog becoming infested with the tapeworm by swallowing such infested 

 lice. The tapeworm sometimes occurs in man, especially children, 

 infection occurring in the same manner as in the dog. 



Treatment. — Lice may be destroyed by dipping the dog two or, 

 preferably, three times at intervals of from 8 to 10 days in one of the 

 coal-tar creosote dips, diluted as stated on the label 

 for use on dogs. Kepetition at a suitable interval is 

 necessary, as these dips do not destroy the eggs, and 

 the lice hatching from them must be destroyed before 

 they in turn can lay more eggs. Clipping is an aid in 

 treatment, as it removes many of the eggs which are 

 attached to the hairs and permits better contact and 

 penetration by the insecticide. The hair clippings 

 should be burned to destroy the lice and their eggs 

 (nits). Oils, such as castor oil, cottonseed oil, or olive 

 oil, may be used to destroy lice, the oil being left on 

 for several hours and then washed off with warm 

 water and soap. After being oiled, a dog should be 

 kept in a clean box to keep him from rolling in dirt. 

 A thick lather of whale-oil or fish-oil soap, or an emulsion of 8 parts 

 of the soap to 1 part kerosene may be used, but kerosene mast be used 

 with caution, the emulsion well made, and the animal not allowed in 

 the bright sunlight for several hours after treatment. When weather 

 conditions do not permit dipping or clipping, or when clipping is 

 undesirable, palliative measures, not very effect Lve in eradicating 

 lice, may be used. Such measures consist in (lusting the hair 

 thoroughly with pyrethrum powder (buhach or ordinary Persian, 



Figure li.— The 

 biting louse of 

 dogs, Trichodectts 

 lotus. Female. 

 Ventral view. 

 Enlarged. From 

 Neveu - Lemaire, 

 1912. (Measure- 

 ments: Male, 1.4 

 millimeters Ions:; 

 female, 1.5 milli- 

 meters long.) 



