THE PARASITE OF EAST COAST FEVER 793 



Imported animals suffer from the disease but animals born and bred in 

 tick-infested countries have an acquired or transmitted immunity (Theiler). 

 The blood of an immune animal contains the parasite and will infect non- 

 immune animals. 



5. Piroplasma pitheci. 



[A true piroplasmosis occurs in monkeys (CercopitHecus) in Uganda and 

 was first observed by P. H. Ross. The manner in which the disease is trans- 

 mitted is as yet unknown (Nuttall). 



[The appearance of the parasite in the blood and the mode of division is 

 the same as in P. bigeminum and P. canis (p. 788) (Nuttall and Graham- 

 Smith).] 



SECTION IV. THE GENUS THEILERIA. 



[Theileria parva. 1 ] 



[Rhodesian fever of cattle (East coast fever, tropical piroplasmosis) is due 

 to an infection with a blood parasite which resembles the parasite of red-water 

 in that it is transmitted by ticks (Rhipicephalus appendiculatus and R. simus 

 [and other species of the same genus]) but differs from it both in morphology 

 and in the fact that it cannot be transmitted by inoculation. ] 



According to Theiler, Rhodesian fever, which is the worst of all cattle diseases, 

 may assume one of two clinical types : an acute rapidly fatal form accompanied by 

 fever, blood-stained diarrhoea, intense jaundice and muscular twitchings, and a 

 chronic form characterized by a transitory attack of fever and jaundice. 



Appearance of the parasite in the blood. In the blood of infected cattle 

 three forms of the parasite are found. In the acute form of the disease the 

 parasites assume a ring or bacillary form and not infrequently the one may 

 be seen to change into the other : they exhibit amoeboid movement, and a 

 small mass of chromatin can be made out. In the chronic form of the disease 

 the parasite appears as a non-motile punctiform mass of chromatin. 



The parasites are very abundant in the blood : in the acute form of the 

 disease 90 per cent, of the red cells may contain them. Generally a few red- 

 water parasites are also seen, in which cases the animals are suffering from a 

 double infection. 



Appearance in ticks. In ticks, Koch observed starred and rounded forms, 

 similar to those seen in the case of Piroplasma bigeminum. 



Microscopical examination. The technique is the same as for P. bigeminum. 



Cultures. Dschunkowsky and Liihs have observed multiplication of the 

 parasite in serum stained with haemoglobin obtained from animals suffering 

 from the disease. 



Experimental inoculation. The disease cannot be transmitted by inocula- 

 tion : even when the blood inoculated is swarming with parasites the animal 

 does not contract the disease. Animals which have recovered from an attack 

 of the disease are immune : the parasite cannot be found in the blood and 

 ticks fed on the blood do not become infected. 



Theiler has recently described a parasite morphologically similar to the foregoing 

 but feebly pathogenic to cattle and very easily inoculable. This parasite is known 

 as Piroplasma mutans (Theiler). 



Piroplasma mutans is very often found in cattle in association with P. bigeminum. 



1 [This parasite is sometimes regarded as belonging to the genus Piroplasma Piroplasma 

 parvum, Babesia parva but Bettencourt, Franca and Borges consider that it differs so 

 widely from the parasites of that genus that it should be separated from them and for 

 that reason created the new genus Theileria. Nuttall is of the same opinion. ] 



