^4-6 SCIENCE IN AFRICA 



borne disease, redwater, was spread in Kenya through the agency 

 of the double-inoculation for rinderpest. It is true that certain 

 catastrophes occurred through animals immune to red-water 

 being used in the preparation of the serum which was subse- 

 quently inoculated into animals susceptible to redwater, but it 

 is definitely concluded now that the disease can have spread no 

 further than the actual animals inoculated, because redwater ticks, 

 wherever they occur, are always infected with the disease. After 

 extensive investigations on the virus of rinderpest, a new method 

 of vaccination with mactivated spleen tissue was developed in 

 Kenya and elsewhere between 1926 and 1928. The vaccine is 

 found in East Africa to give two to two and a half years' immunity, 

 and can be used without the elaborate organization of staff neces- 

 sary for the double-inoculation method. The vaccine is expensive 

 to manufacture, but in the light of recent discoveries on filterable 

 viruses, it is probable that rinderpest vaccine can be considerably 

 improved, and one of the projects upon which work is now being 

 concentrated at Kabete is to discover a method of producing the 

 vaccine at not more than 25 cents per dose. Policy in the control 

 of rinderpest in East and West Africa is framed to suit the individual 

 needs of the territories concerned, and since there is no uniformity 

 of conditions there is no need for uniformity in the method of con- 

 trol. Collaboration exists between veterinary authorities on this 

 subject, but it seems unfortunate that so much laboratory work has 

 to be devoted to the preparation of sera and vaccines for rinder- 

 pest and other diseases. If a means could be devised whereby 

 these necessary materials could be prepared at some central head- 

 quarters, the laboratories and staff in each territory would be free 

 to undertake further research. 



The work on east coast fever at Onderstepoort mentioned above, 

 has been extended in Kenya, where it has been confirmed that a 

 satisfactory method of immunization can probably never be devised 

 since naturally acquired immunity is built up by successive attacks 

 in calf hood (Walker and Whitworth 1929). Experiments have led, 

 however, to an understanding of the value of dipping at short 

 intervals for the prevention of this and other tick-borne diseases. 

 This work has been combined with an intensive survey of the 

 distribution of ticks, as mentioned in Chapter X, and systematic 



