SPOROZOA 457 



thoroughly worked out. The organism stains readily with such 

 dyes as alkaline methylene-blue and by Wright's method. 



Pathogenesis. The relationship of the organism to the disease 

 has been satisfactorily demonstrated by inoculation experiments. 

 The disease in cattle is characterized by fever and a hemoglobin- 

 uria, with considerable destruction of red blood-corpuscles. In 

 acute cases death often occurs in five to eight days after the 

 symptoms are first noted. Those cases in which recovery takes 

 place generally harbor still in their bodies the specific organisms, 

 but remain perfectly well. 



Immunity. As already noted, recovery from disease does not 

 necessarily predicate the disappearance of the organism from the 



Fig. 200. Piroplasma bigeminum, infected red blood cells with 1-4 parasites, 

 a blood-platelet in the center (Sieber). 



blood, and it may persist for years. It has been found that 

 immunity against a fatal attack of this disease may be conferred 

 by inoculation with the blood of immune animals. This results 

 generally in a mild infection, which immunizes against one of a 

 severer type. Such methods of vaccination are quite widely 

 practised. 



Bacteriological Diagnosis. The organism may usually be 

 demonstrated in the blood when stained with Loffler's methylene- 

 blue or Wright's stain. 



Transmission. Natural infection takes place only through the 

 bite of infected cattle ticks (Rhipicephalus annulatus or Boophilus 

 bovis) in the United States and closely related forms in other 



