282 VETERINARY HYGIENE 



spread and especially to be found in large cities. It caused consider- 

 able havoc among horses of the British Army during the war. 

 Predisposing causes are any conditions which lower the vitality 

 (see influenza, strangles) and especially to be noted in young horses 

 are want of condition, fast work and exhaustion. Hunting con- 

 sidered that alterations of temperature are very productive of pneu- 

 monia, and in support of this mentions that pit ponies do not become 

 affected owing to the fact that they are not subjected to much 

 variation of temperature. It is thus essentially a disease of young 

 horses, older animals being comparatively immune to the causes 

 predisposing. F. Smith* does not incline to the view that the 

 disease is contagious, and considers that the causal organisms are 

 probably present in healthy horses, but do not invade the body 

 until the vitality is lowered. It appears to be undoubted that a 

 larger number of cases, and cases of greater severity, occur in winter 

 than in summer (F. Smith). Infection is generally supposed to 

 occur by inhalation. Infection may be spread not only by direct 

 contact but also indirectly by attendants' hands and clothes, by 

 grooming utensils, sponges, &c., and by bedding contaminated with 

 nasal discharge. According to Dieckerhoff the period of incubation 

 is 5 to 10 days, and the mortality 15 per cent. In 7 outbreaks 

 affecting 570 animals described by Lignieres the mortality was 8.8 

 per cent. F. Smith f found a mortality of nearly 18 per cent, in 

 a number of cases of pneumonia, some of which were complicated 

 with pleurisy. 



One attack is considered to furnish a certain degree of 

 immunity, and it is exceptional for animals to be attacked twice 

 at a short interval. 



THE PREVENTIVE MEASURES to be adopted in controlling the 

 disease are essentially the same as those mentioned in the case of 

 strangles and influenza. 



It is not to be supposed that because the diseases strangles, 

 influenza and pneumonia have been described under separate head- 

 ings they do not co-exist. Pneumonia is often seen as a sequel 

 or complication of both strangles and influenza and differential 

 diagnosis may be difficult. 



STRANGLES. 



Strangles is an infectious febrile disease associated with an 

 inflammatory condition of the upper air passages and usually accom- 

 * Journ. Comp. Path., 1897, Vol. X. 

 t Journ. Comp. Path., 1897, Vol. X. 



