STATE HYGIENE 531 



rapidity when horses are huddled together in railway 

 trucks, or on board ship, and this is what might be ex- 

 pected from our knowledge of the parasite. 



Sarcoptic mange is slower in its spread, but as before 

 indicated, infinitely more difficult to treat. 



Symbiotic mange is also slow in progress and it is limited 

 to the region below the knees and hocks. It is a disease 

 confined to the hairy legs of the coarser breed of horses, 

 and its importance is not great. 



The prevention of scabies is a matter entirely under 

 hygienic control ; if the disease occurs in a stud or body of 

 horses there is something wrong. Of course the affection 

 may break out as the result of introducing an affected case, 

 but as indicated above there are cases of the disease in 

 which infection from without cannot be traced, and such 

 are put down as the result of neglect. 



If our supposition is correct that the acari of mange have 

 a saprophytic existence, and only need favourable con- 

 ditions to become parasitic, then we can account for many 

 outbreaks of mange the result of sanitary neglect. 



By far the most favourable condition is a dirty skin ; 

 horses with long coats are very difficult to groom in the 

 winter, and a long and dirty-coated horse is a most favour- 

 able subject for the disease. Clipping as a preventive in 

 cases of this kind becomes a hygienic necessity. 



As might be expected, it is not the working horse with 

 the long dirty coat which is so liable to the disease as the 

 idle horse. An idle horse is always dirtier than a working 

 horse, even when they each receive the same amount of 

 grooming ; work by its action on the skin helps to keep it 

 clean. Dirty skins associated with a debilitated state of 

 the body are a most favourable combination for the pro- 

 duction of the disease. 



Neglect of grooming, want of general care, and insufficient 



food, are the predisposing factors for mange. Given these, 



the production of the disease as an enzootic is only a 



matter of a short time. 



With long-coated working horses the labour of grooming 



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