38 



CIRCULAR 14 8, U. S. DEPARTMENT OF AGRICULTURE 



name given to a 

 contagious 



Fumigating horses with the fumes from burning sulphur (sulphur 

 dioxide) will kill horse lice, but many of the eggs survive, and two 

 treatments two weeks apart are necessary to effect eradication. The 

 advantage of this method of treatment is that it can be used when 

 the weather is too cold for dipping. The disadvantages are that it 

 is necessary to have a gas-tight inclosure and the animal's eyes and 

 nostrils must be kept away from the gas. A concentration of about 

 1 per cent sulphur dioxide is necessary to kill the parasites, and 



serious injury or 

 death may result if 

 the gas comes in con- 

 tact with the eyes or 

 nostrils. After fu- 

 migation it is neces- 

 sary to hand treat 

 that part of the head 

 that was not fumi- 

 gated. (Fig. 26.) 



HORSE MANGE 



Scabies in horses, 

 commonly known as 

 mange, itch, or scab, 

 is a 



group of 



skin diseases caused 

 by minute parasites 

 known as mites, which 

 live on or in the skin. 

 Four species of these 

 parasites are found on 

 domesticated animals, 

 but horses are com- 

 monly affected by 

 only three of them. 

 These parasites are 

 classified zoologically 

 in three different 

 genera — Sarcoptes, 

 Psoroptes, and Cho- 

 rioptes. Mites of the 

 first two genera are 

 shown in Figures 27 

 and 30. 



In obtaining their food from the host and preparing a resting 

 place in or on the tissues, the mites cause wounds or lesions in the 

 skin. As each kind of mite possesses distinctive habits, the location 

 and nature of the lesions in the early stages are more or less charac- 

 teristic. Each kind of mite, therefore, causes a specific kind of 

 mange which is named after the generic name of the mite. Thus we 

 have in horses sarcoptic, psoroptic, and chorioptic mange. The sar- 

 coptic variety is the one most common on horses in the United States. 



Figure 26. — Fumigation with sulphur gas fur lice. Eyes 

 and nostrils must be kept away from the gas. Part of 

 head not fumigated must be hand treated 



