TEXAS FEVER 



of its host. It is unable to come to 

 maturity and reproduce its kind unless 

 it becomes attached to the skin of cattle 

 or horses whence it may obtain nour- 

 ishment. 



The eggs laid on the giound after the 

 female has dropped from the host begin 

 to develop at once. When the embryo 

 is fully formed within the shell it rup- 

 tures this and gains its freedom. The 

 time required from the laying of the 

 egg to the hatcning varies considerably 

 according to the temperature. In my 

 laboratory where the eggs were placed 

 with some moist earth and grass in a 

 fruit jar on the top and outside of the 

 incubator, at a tern perature ranging from 

 70 to 80 degrees Fah., this was accom- 

 plished in 22 days. This was in the 

 summer lime. In the late fall under the 

 same conditions it would undoubtedly 

 take a much longer period. The larva 

 after emerging from the egg is very min- 

 ute, is six legged, and just visible to the 

 naked eye. If the larvae be kept on 

 mois* earth in a covered jar they may 

 remain alive for months, but there is 

 no appreciable increase in size. As 

 soon, however, as they are placed on 

 cattle growth begins. 



On pasiures the parasite soon finds 

 its way upon bovine animals. They 

 attach themselves by preference to the 

 tender skin of the escutcheon, the inside 

 of the thighs and the base of the udder. 

 Yet they may be found on different 

 parts of the body, such as the neck, 

 chest, ears, etc. 



In about a week after the tick in its 

 larval stage becomes attached to the 

 skin of cattle, it goes through the pro- 

 cess known as molting, and the second 

 or nymphal stage of the parasite life 

 commences. After this stage you will 

 notice it has four pair of legs. In about 

 another week molting takes place again, 

 when the tick passes from the nymphal 

 stage to the sexual or adult stage. Im- 



pregnation now takes place, and with 

 the development of the ova in the body 

 the parasite takes in an increased quan- 

 tity of blood, so that it becomes very 

 much larger in a tew days, this applies 

 more especially to the female tick. The 

 rapid growth of the tick at this time is 

 mainly due to the large quantity of 

 blood it takes into its body. When the 

 female has reached a certain stage of 

 maturity it drops to the ground and de- 

 posits her eggs which in due time are 

 hatched out and the above life history 

 is repeated, provided conditions, climate, 

 etc., are favorable. 



iSouthern cattle sent North during the 

 spring and early summer carry on their 

 bodies large numbers of ticks. These, 

 when matured drop off and lay eggs on 

 northern pastures. These hatch and 

 the young ticks soon get upon northern 

 cattle which happen to be in the pas- 

 ture, and attach themselves to the skin 

 when they inoculate the cattle with the 

 pyrosoma bigemium and fever breaks 

 out in fron? one to three weeks there- 

 after. W'hen the weather is cool as in 

 the autumn this period may be a little 

 longer. 



When northern cattle graze upon pas- 

 tures over which southern cattle have 

 passed, tne time when the disease ap- 

 pears depends upon circumstances. 

 When northern cattle are put upon pas- 

 tures immediately after southern cattle 

 have infected them with ticks, it may be 

 from thirty to sixty days or even longer, 

 before the disease appears. This will be 

 readily understood when we recall the 

 life history of the tick. The southern 

 cattle leave onlv matured ticks which 

 have dropped irom them. These must 

 lay their eggs and the latter be hatched 

 out before any ticks can get upon the 

 northern cattle. 



If on the other hand northern cattle 

 are placed upon pastures which have 

 been infected some time before with 

 ticks, the disease will appear much 



