STATE HYGIENE 489 



The definition of an in-contact should be as compre- 

 hensive as possible. 



1. Every animal living under the same roof, or being on 

 the same farm or place. 



2. All animals looked after by the same attendants, or 

 receiving the same food or water-supply. 



3. All animals which have passed through or over roads 

 previously travelled by diseased animals. 



The definition of in-contacts should not be confined to only 

 those animals actually in contact with the diseased. Myste- 

 rious outbreaks of foot and mouth disease are due no doubt 

 to the agency of an intermediate carrier. Dogs may convey 

 the disease, also the boots and clothing of attendants, or 

 the walking-stick of the visitor ; rats, it is suggested, may 

 convey swine fever, while human agency and probably dogs 

 are a fruitful cause. Though it is not proposed here to 

 carry the definition of in-contacts to these, yet in the strict 

 sense of the term they come within the meaning, and such 

 measures as are possible should be exercised to prevent 

 these causes of spread being in operation. 



The nature of the virus must also influence our definition 

 of an in-contact and the measures adopted. The horse that 

 reacts to mallein but shows no clinical sign of disease is not 

 a source of infection, and the limit of in-contact can well 

 be confined to the horse he works with, or those standing 

 on either side of him in the stable. 



The cow with pulmonary tuberculosis may not only 

 directly infect her neighbours by the expectorate, but the 

 latter when dried may infect animals by inhalation which 

 are distant from the centre. 



The animal with anthrax is only dangerous when the 

 blood is shed ; none of those under the same roof run any 

 real risk of infection from the diseased patient. 



The cow with pleuro-pneumonia infects the air of the 

 place she lives in, and is only harmless when dead. 



The evacuations in Cattle Plague contain the virus as 

 does also the blood; pastures and water-supply may in 

 this way be poisoned over a considerable area. 



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