Diseases, Ticks, and their Eradication. 145 



the blood. They have been found m horses, cattle, and sheep in 

 Sonth Africa. Their injection into a susceptible ouimal gives lise to 

 a high fever which, however, has never been noted to end fatally, yet 

 symptoms which point to the destruction of the red corpusclos are 

 present and are easily recognized miscroscopically. We have trans- 

 mitted the parasite artificially by inoculation. Tbe fact interests us 

 that not only the animal which is suffering frojn such a fever, but 

 also the recovered animal, retains the infection in its blood, and such 

 blood proves infective at any time. 



The disease is transmitted by the blue tirdv. We have proved 

 this beyond doubt in several instances, and it lias been verified by 

 Laveran, of the Pasteur Institute in Paris, to w^inm we sent a number 

 of the ticks, which p?;omptly produced the disease in Paris. This 

 parasite does not play an important role as a cause of disease, but may 

 occasionally be responsible for fever and loss of condition in any of 

 the ruentioned animals. We have met with this parasite occasionally 

 in smears sent to u-s from cattle supposed to be suffering from gall- 

 sickness. 



East Coast Fever. 



This formidable disease has, since its introduction into South 

 Africa, played considerable havoc. It is still ])revalent and threatens 

 to spread. It is due to a parasite resembling the group of Piro- 

 plasms. It multiplies within the lymphatic system of the body; 

 from there it invades the blood in such enormous numbers that liiially 

 almost every corpuscle contains one or more parasites. Uniike the 

 other Piroplasms which we have described, it canses the destruction 

 of the red corpuscles to a slight degree only, and the cause ol death 

 of an animal is due not to an acute anaemia as in the other diseases, 

 but to intoxication by the metabolic products of' the parasite. The 

 disease differs in various respects from the before-described piroplas- 

 mosis and anaplasmosis. It cannot be transmitted by inoculation of 

 blood, but only by intrajugular and intralymphatic injectioji of the 

 juice of lymph glands and spleen tissue taken from a sick nnimal 

 which contains the evolutionary stages of the parasite. The striking 

 difference, however, is that the animal which Jias lecovered from East 

 Coast fever, although immune, does not retain the infection in its 

 blood, hence the immune animal does not spread the disease. In 

 East Africa, where East Coast fever has become enzootic, a chronic 

 foTin of the disease has been noticed, characterized by the enlargement 

 of the lymphatic glands, which have been found to contain the 

 evolutionary stages of the parasite (the so-called blue or Kochs 

 bodies). It is thus probable that chronic cases may maintain the 

 infection of the tick, which, as many experiments have shown us, is 

 not maintained by the immune animal. The presence of evolutionary 

 stages, Kochs bodies, are the chief distinguishing factor between 

 Gonderia m,utans, the benign form of gall-sickness, and East Coast 

 fever, the parasites found in the blood being otherwise morphologically 

 identical. The parasite of East Coast fever represents a diifercnt 

 genus (and family) which received the name of Theileria (family 

 Theileridae), and the parasite is called Tlieilenn parro. The lisease 

 is transmitted by ticks, namely the red tick, the blown tick, and the 

 black-pitted tick, as Mr. Lounsbury, Chief of the Division of Ento- 

 mology, and I have proved in numerous experiments. The incuba- 

 tion period when transmitted by ticks varies from six to eighteen 



