Diseases Peculiar to Soutii Africa 



South African Horse Sickness 



What It ISi Horse sickness is a peculiar epizootic disease of South 

 Africa, affecting horses, asses and mules, but the two latter show a 

 greater resistance to the disease than the horse. It exists in all territories 

 and colonies south of the Equator, and has been known in Cape Colony 

 since 1780. In a report of the late Lieut.-Col. Nunn, D. S. 0. A. V. D. 

 of October, 1888, he describes four kinds of Horse Sickness; (1) Acute or 

 Pulmonary, (2) Blue Tongue, (3) Dikkop, and (4) Sub-acute or Bilious 

 form. It affects isolated horses as well as those in troops, and sometimes 

 the old before the young, appearing as often among those in the open air 

 as those kept in sheds. 



The first form is rapidly fatal, while the form known as the Dikkop, 

 although fatal, has a slower course. It prevails mostly in low-lying dis- 

 tricts, in kloofs several thousand feet above sea level, while districts with- 

 out kloofs or valleys only a few feet above sea level are free, if they are 

 some distance from the sea, probably owing to there being less moisture 

 in the atmosphere. 



The Horse Sickness season begins about November and lasts till about 

 May. If rains come early and the summer season is wet, then this dis- 

 ease is rife, but if it is a dry summer very few cases occur. February, 

 March, and April are generally the w^orst months for Horse Sickness, and 

 on moist days with the air humid and the temperature high, the disease 

 is most prevalent. 



CausCi The cause of Horse Sickness is at present undiscovered. 

 Probably the micro-organism is very minute, for under the highest power 

 of the microscope, it is invisible, and passes through the best made filters. 

 This is proved by the fact that filtered blood when injected into the horse 

 produces the disease. The following are some of the leading theories and 

 ideas, as to the possible modes of infection. The organism evidently re- 

 quires heat and moisture for its propagation and vitality ; and it appears 

 to have a miasmatic origin, and to be transmitted by dews, fogs, and 

 winged insects. The writer has known cases to occur in infected districts 

 by the animal eating dew-laden grass before the sun has had time to drive 

 off the dew. Inoculation by mosquitoes, etc., is undoubtedly a very prob- 

 able mode of infection. Mosquitoes and other winged insects are likely 

 carriers of the disease when one considers the vast numbers in which they 

 are bred in stagnant waters and kloofs saturated with dew. 



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