332 DISEASES OF CATTLE. 



BUFFALO GNATS. 



[See discussion of these parasites in chapter on " The animal parasites of cattle."] 



HORN FLY (ILEMATOBIA SERRATA). 



[See discussion of this parasite in chapter on "The animal parasites of cattle."] 



TICKS. 

 [See discussion of these parasites in chapter on " The animal parasites of cattle."] 



FLIES. 



[See discussion of these parasites in chapter on "The animal parasites of cattle."] 



RINGWORM (TINEA TONSURANS AND TINEA FAVOSA). 



Ringworm is an affection of the skin, due to a vegetable parasite. 

 Tinea tonsurans is due to the presence of a minute or microscopic fun- 

 gus — the Trichophyton tonsurans. It affects the hair and the epidermic 

 layer of the skin, and is highly contagious, being readily transmitted 

 from one animal to another. This fungus consists of spores and fila- 

 ments. The spores, being the most numerous, are round, nucleated, 

 and seldom vary much in size. They are very abundant in the hair 

 follicle. The filaments are articulated, waving, and contain granules. 

 This disease is productive of changes in the root and shaft of the 

 hair, rendering it brittle and easily broken off. 



Symptoms. — This disease becomes manifest by the formation of 

 circular patches. on the skin, which soon becomes denuded of hair. 

 The cuticular layer of the skin is slightly inflamed, and vesication 

 with exudation occurs, followed by the formation of scaly, brittle 

 crusts. The patches appear silvery gray when incrusted, and are 

 mostly confined to the head and neck. It is a common disease among 

 young cattle in the winter and spring. Very early in the development 

 of the patches the hairs split, twist, and break off close to the skin. 

 This disease is attended with more or less itching. It is communicable 

 to man. 



Tinea favosa is due to another fungus, the Achorion schonleinii. 

 This enters the hair follicle and involves the cuticle surrounding it, 

 small crusts form which increase in diameter and thickness and then 

 become elevated at their margin, forming a cup-shaped scab, the 

 favus cup, which gives the disease its distinctive character. The 

 number of these cups varies from a few to many hundreds. The hairs 

 involved become brittle and broken, fall off with the crusts, leaving 

 small bald patches. The crusts are of a pale or sulphur-yellow color 

 at first; as they grow older they turn darker, or to a brown color. 

 This form of ringworm has a peculiar odor, resembling that of mice 

 or musty straw. It is occasionally communicated to cattle by man, 

 mice, cats, etc., all being subject to this disease. 



