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SOME OBSERVATIONS CONCERNING THE TRANSMISSION 
OF EAST COAST FEVER BY TICKS. 
By Dr. Arnold Theiler, C.M.G., Acting Director of Veterinary 
Besearch. 
(Read August 16, 1911.) 
It has been proved that Theileria parva, the cause of East Coast Fever, 
can be transmitted by at least five different species of ticks of the genus 
Bhipicephalus (viz., Bh. appendiculatiis , Bh. evertsi, Bh. nitens, and Bh. 
capensis). Of these, Bh. appendiculatiis is the commonest in South Africa 
and in the regions in which East Coast Fever is known generally (Uganda, 
British, and German East Africa). They were almost exclusively used in 
my experience on East Coast Fever. 
The following observations, which were made in connection with 
experiments undertaken for other purposes (mainly to get material for 
the artificial transmission of the disease, and to test the resulting 
immunity), form an interesting addition to and confirmation of facts 
which have already been established concerning the transmission of East 
Coast Fever by means of ticks. 
EXPERIMENT No. 1. 
"A." TO DEMONSTRATE THE FACT THAT BROWN TICK IMAGINES, WHICH 
AS LARV^ HAD BECOME INFECTED WITH EAST COAST FEVER, 
AND HAD TRANSMITTED THE DISEASE IN THEIR NYMPHAL 
STAGE, ARE NO LONGER INFECTIVE FOR SUSCEPTIBLE CATTLE. 
(a) Rhipicephalus appendiculatus, imago (Ref. No. 268). 
Note. — The adult females originated from Natal on January 12, 1910 ; 
the eggs were laid on January 18, 1910, and hatched into larvae in the 
laboratory on February 18, 1910. 
Infecting the Ticks. — The larvae were fed on Heifer 923 from March 20 
to 23, 1910, that is, from the 20th to 23rd day of the disease, and at a 
