790 PATHOGENIC PROTOZOA 



six-legged larva or seed tick appears, and promptly climbs up on the 

 nearest vegetation, grass, weeds or bushes to lie in wait for a warm- 

 blooded host. Although while on vegetation seed ticks do not take 

 food nor grow, their endurance is great, and during the colder parts 

 of the year they may live for eight months. The next stage begins 

 after the seed tick has found a host, when it sucks blood, increasing 

 in size and soon (five to twelve days) molts and a new form, the eight- 

 legged nymph, appears. In five to eleven days more a second molt 

 occurs and the tick is then sexually mature and males can be dis- 

 tinguished from females. The female does not move about on the 

 animal, but the male seeks her out, and after fertilization growth goes 

 on rapidly until the engorged female drops to the ground. To sum- 

 marize : On the ground is the engorged female, the eggs and seed ticks ; 

 on the animal is the seed tick, the nymph, the sexually mature adult 

 and finally the engorged female. The infected female tick transmits 

 the babesia to the larvae through the eggs, but does not herself bite 

 nor convey the disease directly to another animal. 



It is evident that the tick may be attacked in the pasture or on 

 the cattle. Pasture rotation is one of the methods recommended by 

 the Agricultural Department, and it rests upon the fact that all the 

 ticks will die from starvation in an unused pasture in from six to 

 twelve months, varying with the climate, the shorter period holding 

 true for warmer localities. By changing pastures a farm may be freed 

 of ticks in four and a half or eight months, depending on the plan fol- 

 lowed. For economic reasons, lack of sufficient pasture land, etc., this 

 plan has not been widely adopted. A second plan, that of dipping, 

 has been more successful. The cattle are driven through a large dip- 

 ping vat at intervals of two weeks (never more than three must 

 elapse) until they and the pasture are free from ticks. The fluid in 

 .the dipping vats is an alkaline solution of arsenic ; oil dips are little 

 used at present. Arsenical dips are cheap, easily prepared and effi- 

 cacious, two or at most three dippings, at ten-day intervals, being suf- 

 ficient to free heavily infected cattle, and if they can then be put on 

 tick-free pastures the problem is solved. If no tick-free pastures are 

 available, dipping must be continued, as above, until the animals 

 remain permanently free.. 



The prevention of tick-borne disease is to be solved, therefore, by 

 tick eradication, and experience in the Southern states has shown this 

 to be a practical measure. 



