PROTOZOA IN BRITISH EAST AFRICA 
37 
plication of the parasite in the circulation such as occurs in 
Babesia is practically unknown, and, since the percentage of 
invaded corpuscles at the acme of infection is frequently 90 
per cent., it is obvious that a factory must exist somewhere 
within the body from which the red blood corpuscles become in- 
vaded. It is suggested that the red blood corpuscles act merely 
as mechanical carriers of the parasite, enabling the ticks which 
are feeding on the peripheral capillaries to acquire infection and 
so maintain the species, and that this factory is in all probability 
represented by certain forms of Koch’s bodies. The view that 
Koch’s bodies have no connexion with Theileria was advanced 
by Martin Meyer, but has received scanty support. In the 
opinion of all who have had experience of East Coast Fever, 
these bodies are diagnostic of the disease, and must be accepted 
as part of the life cycle of the intracorpuscular form. 
Gonder has recently published his observations on Koch’s 
bodies in relation to Theileria and has indicated the place 
held by them in the life cycle. 
Transmission. Loundsbury was the first to prove the 
transmission of East Coast Fever by means of a tick, Rhipice- 
phalus appendiculatus (the brown tick). Theiler subsequently 
substantiated this and further proved that Bh. simus (the 
black-pitted tick), Bh. capensis, Bh. evertsi (the red-legged 
tick), and Bh. nitens may carry on the development of Theileria. 
The transmission of the parasite is effected by nymphae and 
by adults which have acquired the infection as larvae and 
as nymphae respectively. Ticks which make use of at least 
two hosts, more commonly three, must be viewed with suspicion, 
and it is possible that Bh. pulchellus, so common on the Athi 
Plains, may also act as a carrier. 
A larva or nympha having fed on an infected animal 
drops off when replete and takes three weeks or more, according 
to season, to moult. It is only after this change that such 
a tick becomes capable of giving infection, and this knowledge 
is of the utmost practical value, since by its scientific application 
one can save from contact and infection all non-infected 
animals. 
Pathogenesis. East Coast Fever first manifests itself by a 
rise in temperature between the tenth and twentieth day after 
