286 African Horse-8iekness. 



this is only possible in young Angora goats, their blood l^ecom- 

 ing infections to horses and mules, but not for other goats. On 

 the other hand they succeeded by intravenous injections of large 

 quantities of unfiltered horse blood, to cause severe illness in 

 dogs, and to infect other dogs as well as horses with their blood; 

 McFadyean however failed to observe any manifestations of 

 disease in three dogs after subcutaneous injections of small 

 quantities of virus. Man is not susceptible, as has been estab- 

 lished by Rickmann and Kaestner through subcutaneous injec- 

 tions on their own bodies. 



Edington and Morton Coutts consider horse sickness and heart 

 water (see p. 257) as identical, or at least as closely I'elated diseases. 

 They succeeded in producing in horses a disease resembling horse 

 sickness, with the virus of goats affected with heart water. The virus 

 of this disease however possessed only a slight virulence for horses. 

 This view is disputed by Theiler and Stockman, as their experiments 

 have shown that goats treated with the virus of horse sickness remain 

 susceptible for heart water, and likewise horses inoculated with heart 

 water blood may later become affected with horse sickness. 



Whether there exists a close relation between horse sickness and 

 infectious anemia (see that disease), in the sense that the anemia rep- 

 resents a mild form of horse sickness, is not conclusively established, 

 and requires closer investigation. 



Natural infection occurs in the periods of the year men- 

 tioned, usually out of doors and at night; keeping the horses 

 in the same places in day time from the time when the dew dries 

 until sunset, as well as during rainy weather, is not dangerous 

 for them. The first frost usually terminates the disease, so that 

 from the eighth day following it no more cases occur (in dry 

 weather the disease occurs only very exceptionally). Although 

 the disease may be produced by feeding great quantities of 

 virus, the observation that in the dangerous pastures horses are 

 not protected by muzzles, indicates that the infection is trans- 

 mitted by some insect or fly. According to Pitchford anopheles 

 mosquitoes and stegomya which have been within 48 hours upon 

 the body of an affected animal serve to transmit the disease to 

 healthy horses; Reinecke succeeded by a test in Germany in 

 producing a fatal disease in one horse by subcutaneous injec- 

 tions with an extract from ticks which he had collected in the 

 African horse-sickness district one year before. This may ex- 

 plain why smoke near the horses (Theiler), or keeping them in a 

 stable protected by a net (Pitchford), prevents the disease. 



Anatomical Changes. The autopsy reveals in locations 

 varying from case to case, a gelatinous infiltration of the sub- 

 cutaneous and intermuscular connective tissue, especially 

 around the eyes and the region of the throat. There is acute 

 swelling of the superficial lymph glands, severe catarrhal swell- 

 ing of the mucous membrane of the stomach, the anterior por- 

 tion of the small intestines and occasionally also of the large 



