538 REPORT—1905, 
pathological science. They discovered that it was caused by the presence in the 
red blood corpuscles of a protozoal parasite closely related to the parasite found 
in E.C.F.—the Piroplasma parvum, This organism is called Piroplasma bigeminum. 
They further discovered that this parasite was conveyed from sick to healthy cattle 
by means of a tick. They also showed that the cattle born and bred in certain 
southern districts are immune to the disease, whereas cattle in the northern dis- 
tricts are susceptible. Hence, if southern cattle were driven into the northern 
district, they gave rise to a fatal disease among the northern cattle; and, vice versd, 
if the susceptible northern cattle were driven into the southern district among the 
apparently healthy cattle of that district, they took Texas Fever and died. 
Texas Fever was introduced about 1870, and is now endemic throughout most 
of South Africa. For many years the native cattle have been immune to the 
disease ; that is to say, on account of being born and bred in a Texas Fever 
locality they had inherited a degree of resistance to the diseasé which enabled 
them to pass through an attack when they were young, and so they became im- 
mune. But there is one peculiarity about Texas Fever which does not occur in 
Rhodesian Tick Fever, and that is that the blood of an animal which has recovered 
from Texas Fever remains infective—the germs remain latent—and so the native 
cattle of South Africa, although apparently healthy, are capable of infecting im- 
ported susceptible cattle with this very fatal malady. This is what makes it so 
difficult to import prize stock into this country. 
When the Boers visited Mooi River, at the beginning of the war, they found 
a prize short-horn carefully stabled in Mr. P. D. Simmon’s farm. They killed most 
of his stock for food, but left this short-horn bull alive. When they left the farm 
they turned this bull into the nearest field, in order, of course, that it might procure 
food, They had much better have eaten it. It promptly took Texas Fever and died. 
This disease, then, has become of secondary importance to South Africa in these 
days. ‘The native cattle have become naturally immune, and the disease is only 
fatal to susceptible imported cattle. This, of course, discourages the importation of 
prize stock ; but with the knowledge we possess it ought to be possible, by good 
stabling and prevention of contact with tick-infected cattle, to keep the prize stock 
alive for a reasonable time. The question of the feasibility of immunising the 
prize stock while calves in England might be considered. 
In regard to methods of conferring immunity on susceptible cattle many have 
been tried, but none are absolutely free from risk. 
We may sum up in regard to Redwater or Texas Fever by saying that our 
knowledge of its causation and the methods of prevention are much the same as they 
were ten years ago. The work done by Smith and Kilborne on this disease was of 
such a brilliant nature, and was done so thoroughly, that little has been left for 
later workers to do. 
3. Biliary Fever of Horses, Mules, and Donkeys. 
This is a disease of horses, mules, and donkeys very similar to Redwater in 
cattle, and is caused by a closely allied parasite, the Prroplasma equi, discovered 
for the first time in South Africa by Bordet, Danysz, and Theiler, and named by 
Laveran of Paris. 
It is similar to Redwater, in that animals which have recovered from the 
disease remain a source of infection during the remainder of their lives to 
susceptible animals. The native South African horse is, like the cattle, immune 
to the disease. It is also conveyed by a tick, which has been shown by Theiler 
to be the ‘red tick’ (2thipicephalus evertst), the infection being taken in the 
nymphal and transferred in the adult stage. Theiler has also made the very 
important observation that if a horse is injected with blood from a donkey which 
has recovered from the disease, as a rule a mild form of the disease is produced, 
so that this opens up a method of immunising susceptible horses which may 
probably prove of practical value. Theiler has also made another curious dis- 
covery. This disease of horses was found to greatly complicate certain immunising 
experiments he was making against Horse-sickness. He found he was intro- 
ducing the Piroplasma equi at the same time he injected Horse-sickness virus, 
