MICROBIAL DISEASES OF MAN AND DOMESTIC ANIMALS 895 



The parasite is a pear-shaped organism which usually lies within a red cell. It 

 measures from 2^1 to 4ju in length and about in in breadth. In fresh preparations 

 they appear as refractile bodies possessed of slight amoeboid movement; in stained 

 preparations they are seen to consist of a blue-staining cytoplasm which contains a 

 mass of chromatin at its broader end. Multiplication is accomplished by simple 

 division into two or more parts; it is possible that schizogony and sporogony may 

 also occur. The parasites are often very scarce in the peripheral circulation 

 but are much more numerous in the organs and particularly in the spleen. The 

 disease can be transmitted, experimentally, from bovine to bovine by the inocula- 

 tion of blood which contains parasites; normally, it is transferred from animal 

 to animal by the bites of a tick. The species of tick which carries red water is not 

 the same in all parts of the world. 



B 



D 



fi 



H 



K 



m 



FIG. 191. Babesia bigemina. Various stages of development in red blood cells. 

 A, young parasite; B, a twin-form; C-E, a multiple division; F-K, large pear-shaped 

 forms. (After Doflein.} 



Ten days intervene between the bite of the infecting tick and the 

 first sign of the infection. The temperature rises, it may be, to 106, 

 or more, and it remains high for a week. The animal is evidently very 

 ill, it has no appetite, and it rapidly loses strength and weight. Many 

 red cells are destroyed and anaemia may be marked. The urine is 

 albuminous and it is red because of the haemoglobin which it contains. 

 Death may occur in very acute cases as early as the second day. 

 Animals which recover from a severe attack are usually immune to the 

 disease. The immunity is not an absolute one, however, for blood 



