298 SCIENCE IN AFRICA 



development of the parasite in both intermediary and definitive 

 hosts is a useful contribution to knowledge of the life cycle of piro- 

 plasms, a subject which, in recent years, has received a good deal 

 of attention in various parts of the world. Earlier work in South 

 Africa by Theiler and Lounsbury has shown that in addition to 

 R. appendiculatus certain other African species of the genus Rhipice- 

 phalus are capable of acting as experimental vectors of east coast 

 fever. At the present time there is in progress at Kabete a systematic 

 revision of the transmission of this disease. Different species of ticks 

 are being examined with regard to their ability to transmit pure 

 infections and the characters of the transmitted disease are being 

 observed for signs of difference in the disease as transmitted by 

 different hosts; already a new experimental transmitter has been 

 discovered in Hyalomma aegyptisum impressum. In 1929, an ento- 

 mologist was engaged to carry out a tick survey in Kenya in order 

 to ascertain the exact distribution of i?. appendiculatus, and to inves- 

 tigate the ecological factors responsible for it. Already the distri- 

 bution of tick species has been plotted (Lewis 193 1-4) and climatic 

 conditions likely to affect this distribution are being studied in 

 the laboratory. Periodic collections of ticks have been submitted 

 to Kabete also from Tanganyika and the Gold Coast. It is of 

 interest to note that although east coast fever is unknown on the 

 west coast of Africa, R. appendiculatus has appeared in collections of 

 ticks from Pong-Tamale in the Gold Coast. 



Theileria parva, the parasite of east coast fever, does not pass 

 from adult to larval stage through the &gg of the tick; on the other 

 hand, in the Babesia group, which includes the parasites of red- 

 water of cattle, biliary fever of horses, and tick fever of dogs, 

 hereditary transmission is effected. The main vectors of the latter 

 group of piroplasms belong to the genus Boophilus, all of which are 

 continuous feeders; that is to say, they do not drop to the ground to 

 moult from larva to nymph and nymph to adult, as do members 

 of the genus Rhipicephalus, but remain on the same host during all 

 three instars; and it is, therefore, necessary that the protozoan 

 parasite should pass through the egg of the tick in order to ensure 

 its transference to a fresh host. 



Two other Theileria species, T. annulata and T. dispar, cause 

 serious diseases of cattle, the former in Asia and the Mediterranean 



