CHAPTER II. 

 PARASITIC SKIN DISEASES. 



FLEAS. 



Description. —Fleas are large enough to be seen with the 

 naked eye, but magnification is necessary to distinguish the 

 species. They are a jumping insect without wings, brown in 

 color and about 2 to 4 mm. long. The female is the larger. 

 They obtain nourishment by sucking blood. They readily 

 pass from one animal to another and may reside in dust, 

 filth, etc. The eggs are dropped or deposited on the ground 

 or floor and hatch in six to twelve days . The final transforma- 

 tion into perfect insects requires three to five weeks depending 

 upon the temperature. 



Occurrence.— The dog is the most commonly affected of 

 the small animals, with the Ctenocephalus canis, the 

 common dog flea. The Pulex irritans of man will also live 

 on dogs. The cat (Ctenocephalus felis) is rarely affected 

 except when closely associated with infested dogs. They 

 suffer considerable annoyance but the fleas soon leave of 

 their own accord. Hares and rabbits harbor the rabbit flea 

 (Pulex gonivcephalus) , but may also be the hosts of the dog 

 and human flea. On fowls, pigeons and other birds the bird 

 flea (Pulex avium) is parasitic. 



Symptoms.— Fleas are most common on dogs and pigeons. 

 Sedentery, feeble or young animals, or those nursing young, 

 or birds incubating eggs, are particularly susceptible; also 

 animals kept in close quarters. Fleas are tormenting and 

 harm the animal chiefly by disturbing rest and quiet. Large 

 numbers may produce chronic skin eruptions, but the most 

 damage to the skin results from frequent and persistent 

 scratching which produces irritated areas on the skin of the 

 neck, back of the ears, and back of the forearm. The skin 



