300 A TICK-RESISTANT CONDITION IN CATTLJE. 



3. Transmission by contact : — By this Mr. Hull raeansf 

 that the resistant condition is " picked up " naturally, i.e., 

 that larvse which hatch from the eggs laid Ijy the few tick» 

 maturing on resistant cattle, convey " something " derived 

 from such animals to those which they infest and thereby 

 set up resistance. We have already stated our inability to 

 find any organism in smears of the exudation. Larvae- 

 from ticks taken from resistant animals were applied in 

 considerable numbers and on several occasions to cattle in 

 Brisbane during 1916. The latter did not show any 

 difference from the controls in regard to tick attack, all 

 being very lightly infested. The application of larvse to 

 animals which had been " vaccinated " did not meet with 

 success. 



Two l>atches of larval ticks, one lot being the progeny 

 of four engorged females taken from Rosie, the other the- 

 offspring of six taken from Sunset, were sent on 3rd April, 

 1918, to Miss M. Walker, Woolooga, who replied on 18th. 

 June, that on two or three occasions, after applying these- 

 larva? to an experimental "heifer, there appeared in the 

 vicinity of the anal and genital region of the latter, abiuit 

 two days after application, tiny yellow blisters which, on 

 being squeezed, exuded a drop of clear yellow- fluid. In 

 July, another letter was received in which Miss Walker 

 stated that quite similar blisters had appeared on the animal 

 after the application of ordinary larva?. 



A number of heifers were brought from Kosewood to 

 Eumundi and allowed to remain in Mr. Hull's paddocks for 

 a certain length of time to ascertain whether they would 

 acquire resistance. They were not subjected to vaccination, 

 and were treated Avith an arsenical solution only at the time 

 of leaving Eumundi for Rosewood. Their condition while 

 at Eumundi has been noted elsewhere in this report. We are 

 awaiting observations as to the effects noticed during the 

 forthcoming tick season. 



Our examination of Mr. Hull's records re\'eaLs the fact 

 that of the stock which never acquired resistance while oa 

 his property— young animals {i.e., calves and yearlings) 

 excluded — four remained there two yoars without acquiring 

 it ; two, three years ; four, four years ; nine, fivc^ years ; one,, 

 six years ; and one, seven years. 



