SPOROZOA 789 



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 (Mar gar opus annulatus)* 



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 



FIG. 197. THE TEXAS FEVER TICK (Margaropus annulatus). (Rosenau, "Preven- 

 tive Medicine and Hygiene.") 



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 

 ea^ch female. The female tick dies in a few days after the egg-laying 

 has been completed. The eggs soon hatch (after nineteen days in 

 summer to one hundred and eighty-eight in winter) and a small, oval, 

 _ - _-^ , _ 



i Farmers' Bull. No. 498, U. S. Dept of Agri. 



