BY T. HARVEY JOHNSTON AND M. J. BANCROFT. 221 



These facts are stated in order to emphasise the serious- 

 mess of the tick problem in such an important beef and 

 -butter-producing State as Queensland. 



Tick infestation may lead to one or both of the follow- 

 ing complaints : Tick fever or Piroplasmosis (often termed 

 Babesiasis, Texas fever, or redwater) and Tick ivorry, 

 'Often called tick poverty or tick anaemia. 



Tick Fever. 



The term " immunity "is commonly used in Queens- 

 land in connection with the tick but it is not strictly correct*. 

 We speak of cattle becoming rendered naturally or arti- 

 ficially " immune "" to tick fever, whereas this so-called 

 "immune" condition is now known to remain iisually for 

 -a comparatively short time — one or two years (Dodd, 

 1909, p. 84) though a case of 12 or even 13 years persistence 

 is known (Schroeder, 1905, p. 71 ; Wallace, 1908, p. 320)— 

 Tinless maintained by subsequent re-inoculation of the 

 animal| (Smith and Kilborne, Hunt, Tidswell, Pound, 

 Wallace, 1908, p. 320). This occurs naturally in tick- 

 infested districts through the agencj^ of larval ticks that 

 are infected with the micro-organism Babesia bovis {Piro- 

 plasma bigeminum) which causes the tick fever. Such 

 larvae are born infected through some of the organisms 

 in the parent reaching its ovary and thus infecting the eggs 

 from which larvae ultimately develop. J The condition can 

 also be brought about by inoculating the cattle with ox 



*" The condition is termed ' immunity ' simply for want of a better 

 and more descriptive name. It is in fact a very mild chronic form of 

 Texas fever, positively associated with the infectious agent of the 

 raffection." (Schroeder and Cotton, 1905, p. 76). " It is merely a 

 -tolerance for the infectious organism." (Schroeder, 1905, p. 62). 

 Lignieres has also discussed thj question as to whether the condition 

 is an immunity or only a tolerance. 



tNuttall, G., in his lecture on Piropla-smosis (Herter Lectures, iii., 

 John Hopkins Hosp. Bull., 24, 1913), has stated that recovered or salted 

 .animals are not susceptible to reinfection. This is contrarv to 

 Austrahan experience. He has pointed out (p. 309) tliat animals which 

 have recovered from cattle tick fever caused by Piropkusma divergent 

 Are susceptible to Texas fever (due to P. bigeminum). 



JCrawley. Jour. ParasitoL, 2, 1916, p. 87. 



