SPOROZOA 1133 



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 par- 

 ticular 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. 

 Quarantine of cattle from infected regions is absolutely necessary to 

 prevent the spread of the disease, since all immune animals are also 

 carriers. Young animals, between nine and twelve months of age, 

 may be inoculated with the blood of those which have recovered, five 

 to ten c.c. being given in a single dose ; the disease lasts two to three 

 days, and the mortality is not great, as eighty to ninety per cent of the 

 inoculated animals recover and remain immune. Inoculation, how- 

 ever, is a measure of doubtful value and some means of tick eradi- 

 cation should be used if the disease is to be permanently stamped 

 out. 



Life History of the Tick (Margaropus annulatus) 5 



The tick's life is divided into two stages, one part passed on cattle 

 and another part passed on the ground. The mature female, as 

 found on cattle, is about half an inch in length, plump and olive green. 

 When fully engorged with blood from its host, it drops to the ground, 

 seeks a sequestered hiding place and if it escapes birds, ants and 

 other enemies, begins after a few days of warm weather to lay eggs. 

 These are small, elliptical, at first light, later dark brown, and are 

 cemented together in irregular masses by a sticky secretion; in num- 

 bers they vary from a few hundred to more than five thousand for 



"Farmers' Bull. No. 498, IT. S. Dept. of Agri. 



