466 GENERAL DISEASES. 



Africa is that the disease runs its course in a couple of hours, or 

 even less ; the cause of this mistaken opinion being evidently 

 want of ability to recognise the synxptoms until they are of a well- 

 marked character. Usually, death, principally from suffooatioo, 

 comes on suddenly. 



In dikkop, the chief manifestation is an enormous swelling of 

 the head, neck, and lips. The lips usually swell so much that 

 they fall back and expose the front teeth of the lower jaw. The 

 swelling of the head and neck in dikkop closely resembles that 

 seen in the chest form of anthrax (p. 4:59). In dikkop there is 

 always more or less congestion of the blood vessels of the lungs ; 

 and in paardziekte, more or less transudation' of liquor sanguinis 

 into the tissues immediately underneath the skin of the head and 

 neck. Consequently these forms are never quite pure. 



In the blue tomgue variety, symptoms of pneumonia are not very 

 prominent. The muzzle, lips, and tongue become swollen. The 

 tongue also assumes a dark-blue appearance. It turns cold, and 

 often becomes too large to be retained in the mouth. Thick, dirty 

 saliva falls from the mouth. The blue colour of the tongue is due 

 to congestion of the veins of the part. 



ANIMALS ATTACKED.— The disease appears to be practically 

 limited to the horse tribe (equidaj). Donkeys and mules are less 

 susceptible than horses, and zebras are seldom if ever attacked. 

 A disease has recently been identified which occurs to a limited 

 extent among cattle as being probably of the same nature, while 

 a disease which occurs widely throughout the Eastern Province 

 among high-bred goats and sheep is closely related in its pathology _ 

 with this malady. It has been shown by experiments that human 

 beings are not susceptible to horse sickness. 



GEOGEAPHICAL DISTEIBUTION.— It appears to be confined 

 to Africa, and attacks horses in all parts of the southern portion 

 of that continent. It occurs every year in the Transvaal and 

 Rhodesia; but in Cape Colony, Orange River Colony, and Natal, 

 it takes a widely-spread (epizootic) character only in certain years, 

 although a few cases may be found annually, here and there, in 

 these parts. 



HISTORY AND MORTALITY.— The following outbreaks have 

 been recorded: 1780-81, 1819, 1839, 1854-55, 1891-92 (Cape 

 Colony), 1888 (Natal), and 1893-94 (Orange River Colony). The 

 loss of horses is very great during an outbreak of this malady. 

 In 1854-55, 64,850 horses died of it, and in 1891-92, 13,979 horses 

 and 149 mules. In Rhodesia the annual loss is about 90 per cent. 



