296 AGRICULTURAL BACTERIOLOGY 



The disease is often called tick fever because of the method 

 of transmission, and red or black water from the dark urine. 

 Of the ticks that are to be found on cattle, but one, Mar- 

 yaropus annidaius, is concerned in the transmission. The 

 female tick that is infected with the parasitic organism 

 drops off the host animal to lay the eggs on the ground, 

 where they hatch in from thirteen days to six weeks, de- 

 pending on the temperature. If the young seed ticks come 

 in contact with an animal, they attach themselves to the 

 inside of the thighs and flanks, along the belly and brisket, 

 inside the fore legs, and around the base of the tail. They 

 remain attached to the animal with which they come in con- 

 tact, living on the blood. 



The protozoa causing the disease pass from the female 

 into the egg, and thence into the seed tick, which infects the 

 host animal. If the host is immune, no harm results; but 

 if the animal is susceptible, a fatal form of the disease is 

 usually produced. Young animals are not very susceptible 

 to the disease. When raised in contact with the ticks, they 

 gradually become infected with the protozoa during the 

 time when the immunity is so high that a fatal form of the 

 disease is not occasioned, and a permanent immunity is 

 produced by the mild attack. The loss from the disease is 

 not so much from death of animals as from the fact that 

 cattle can not be sent from infected regions to free areas. 

 Thus Southern cattle can not be shipped to the Northern 

 cattle markets, except under certain restrictions that add to 

 the cost of marketing. In the markets the cattle from in- 

 fected regions are sold at a lower price than the same grade 

 from a non-infected territory. The ticks are also a con- 

 stant drain on the vitality of the animals, diminishing the 

 milk production and rate of growth. The susceptibility of 

 cattle from free territory is so great that they can not be 

 taken into infected territory without immunization. This 



