788 PATHOGENIC PROTOZOA 



without producing pigment. In cattle, sheep, horses and dogs, the 

 freed hemoglobin is excreted by the kidneys, producing the disease 

 variously known as red water fever, Texas or Southern cattle fever, 

 tick fever, bovine malaria, hemoglobinuria, and others. The parasite 

 is small, two to four microns long and one to two wide, and character- 

 istically occurs in pairs, the narrow ends being united. When the 

 parasite is mature the two daughter cells separate and when liberated 

 by the degenerated erythrocyte attack new red cells. The pear-shaped 

 babesia enters a new cell by its broad end, becomes rounded or ring- 

 like, then ameboid in form, and finally the nucleus sends out a bud ; 

 this divides into two by forking, and as the nuclear matter continues 

 to grow each portion becomes surrounded by cytoplasm and ultimately 

 the two new daughter cells separate from one another. Multiple in- 

 fections of single red cells are common, as many as sixteen pairs 

 having been seen in a single cell. 



Good preparations for clinical work are obtained by some one of 

 the Romanowski stains, but the finer details of the nucleus and cell 

 division can only be studied after iron hemotoxylin staining. 



The parasites, with the exception of Theileria parva, do not disap- 

 pear completely from the blood after the animal recovers from its 

 illness, but remain indefinitely in the circulation, and their continued 

 presence and virulence may be demonstrated by the inoculation of 

 non-immune animals with blood from an animal which has recovered. 



Transmission. Transmission from host to host is by means of ticks. 

 Margaropus annulatus carries Southern cattle fever in the United 

 States, but other ticks are carriers in South America and the West 

 Indies. In general, each species of babesia is specific for a particular 

 animal, and each is carried by a separate group of ticks. 



Clinical Observations. Clinical observations have shown an in- 

 cubation period of about fourteen days; the onset is with fever and 

 the cattle look weak and ill, neither eat nor chew the cud, but stand 

 with sunken head and relaxed ears. A bloody diarrhea sets in 

 early and the urine, which is small in amount, is deep red in color 

 and contains much albumin. The blood shows few parasites at first, 

 but they soon increase and the number of red cells falls rapidly. The 

 mortality varies in different epidemics from five to sixty per cent, 

 but has been as high as ninety in some herds. Young cattle, under a 

 year, have a mild form of the disease, and remain thereafter immune. 



The treatment, once the disease has appeared, is unsatisfactory, 

 since we have no specific, but much may be done by prophylaxis. 



