BY T. HARVEY JOHNSTON AND M. J. BANCROFT. 223 



adult animals is generally high, being often from 50-90%*, 

 "whereas that resulting from protective inoculation is often 

 under 2% (Dodd, 1908, j). 10). Many years earlier, 

 Tidswell gave the percentages as 60-70% and 3-5% 

 respectively (1899a). Pound (1899, p. 100) gave an even 

 lower figure, viz. 1% on a total of over 30,000 head protec- 

 tively inoculated. He also published a list of percentage 

 losses (0.5-5%) experienced b}' a number of Queensland 

 graziers. Dodd, several years later (1908), mentioned 

 that during nine months of 1908 the average mortality in 

 this tState was 1.98% in the case of highl}' susceptible 

 animals (that is, those from herds which had not contracted 

 fever though in fevered districts), and 0.58 in the case of 

 partialty susceptible animals [i.e., those from herds in which 

 tick fever was known to have appeared), while the average 

 total loss from inoculation amongst the animals of both 

 classes was about 1.5%. In 1909 (Dodd, 1909. p. 85) he 

 gave the average loss for 1908-9 as being only slightly 

 over l%t- Mortality is especially high in older animals, 

 in bulls and in very fat or very thin cattle (Tidswell, 1899a). 



The amount of resistance to tick fever displayed by 

 cattle has been summarised thus by Pound (1897, p. 473) : 

 " When ticks first appear in a herd the first animals to 

 succumb to tick fever are })ulls, esjiecially the old ones ; 

 next in order come breeding cattle (cows) ; then bullocks 

 and spayed cows ; but the least susceptible of all are the 

 young animals, and practically speaking, there is little or 

 no mortality from tick fever among yearlings or calves 

 at foot." 



*Smith a d Kilborne (1893, p. 274) in their account of an outbreak 

 in U.S.A., stated t!iat natural immunity of cattle more than a year old 

 in the casj of a;iimals outside of tick-infested areas and which had not 

 previously beei tick-fevered, was so slight that the mortality in many 

 cases was nearly 100%. Still, however, there were animals which had 

 more or less immunity though they had never been previously exposed 

 to the disease. Salmon (1899, p. 221), mentioned that 75-90% of adult 

 cattle in fevered districts died of Texas fever in hot weather in the early 

 days of the outbreak. G. Tucker (in Ann. Rep. Dept. Agr. Qld., 1916-7 

 (1917), j)p. 88-9) referred to recent heavy losses in Northern Queensland 

 owing to tick infestation. 



fSeo also Editorial articles " Inoculation for tick fever " Q.A. J., 2, 

 1898, p. 517, re slight losses experienced. 



