35 



sabcutaneous inoculation of virulent blood, found that they were not 

 protected when exposeci to natural infection. His results after five months' 

 exposure were : Death from heartwater in SOJper cent, of Boer goats ; 

 50 per cent, of Cape sheep ; 40 per cent of Angora goats ; 40 per cent, 

 of merino sheep, and lambs 25 per cent. 



Conclusion. — Immunity acquired by inoculation and increased by 

 hyperimmunisation protected eight cattle against natural infection of 

 heartwater. The immunity conferred on sheep and goats by inocula- 

 tion of virulent blood broke to a great percentage. 



Blood op Immune Animals. — The blood of an ox which had recovered 

 from an attack of heartwater was injected into two susceptible sheep 

 without any result.* The same results were obtained by Lounsburyf , who 

 injected blood of recovered goats into susceptible goats. Further, his 

 experiments with ticks reared on goats which recovered from heartwater 

 demonstrated that these were unable to transmit the disease. 



Conclusion. — Animals which have recovered from an attack of heart- 

 water do not retain the infection in the blood. 



Preventive Value op Serum. — The serum of an immune animal 

 which has been hyperimmunised has acquired preventive qualities which 

 may be summarised as follows : — (1) Mixture of serum and virus, with 

 the excess of the former, injected subcutaneously, did not cause the 

 disease. (2) Serum injected subcutaneously in excess and virus into 

 the jugular vein or subcutaneously prevented a reaction. (3) Serum 

 injected twenty-four hours previously to the virus prevented a reaction. 

 (4) Serum injected twenty- four hours after virus did not prevent 

 development of reaction. 



Conclusion. — The serum of hyperimmunised animals have preventive 

 qualities. 



Resume. 



(1) Immunity in heartwater is not complete ; it can be broken by 

 virus of a different strain. 



(2) Immune cattle seem to have a better protection than immune goats 

 of sheep against virus of different locahties. 



(3) Serum of hyperimmunised animals has protective properties. 



(4) Immune animals do not act as reservoirs. 



II.— PmOPLASMOSES. 



Eedwater of cattle (bovine piroplasmosis). Bihary fever of equines 

 (equine piroplasmosis). Bihary fever of dogs (canine piroplasmosis). 

 Infection due to Piroplasma mutans. 



" ■' Cape Agricultural Journal," Vol. XXI, No. i. 

 t Annual Eeport, Government Entomologist, 1901. 



