232 A TICK-RESISTANT CONDITION IN CATTLE. 



The fact that immunity becomes established in the- 

 case of some ticks is evidence that some substance is injected 

 by the tick. It is reasonable to suppose that the material 

 acts as an antigen stimulating the production of an anti- 

 body (anti-tick toxin) which can combine with the tick 

 toxin and thus confer an immunity. 



In many cases, a more or less marked eosinophilia is 

 produced b}' the action of internal parasites*, and in the 

 case of at least one of them (hydatids) the blood serum has 

 become altered to such an extent that the precipitin reaction 

 can be made use of to detect the presence of Echinococci 

 in the patientf. 



Zinsser} has given a list of the more important sub- 

 stances which, when on injection into the blood of an animal, 

 lead to the formation of a specific antitoxin or toxin- 

 neutralising body, one such substance being spider poison. 

 It seems to us reasonable to expect that such reactions 

 might be given by ticky cattle. It is proposed. \\'ith the 

 assistance of Dr. H. B. Bradley, of the Bureau of Micro- 

 biology, Brisbane, to test the precipitin reaction, using 

 the blood of cattle from non-infected districts {e.g., N.S, 

 Wales), from ordinary infested cattle and from strongly 

 resistant animals. We must remember, however, that 

 " the various antibodies are usually produced Anth more 

 avidity by certain tissues than by others," and that " anti- 

 body formation may be of strictly local character depending 

 upon the point where the antigen is injected."** 



Should such a reaction be obtained from the blood, then 

 one might consider the possibility of using an animal whose 



*Stitt, Practical Bacteriology, Blood work and Animal parasitology, 

 1918, p. 264 ; S. Hawden (" Natural Occurrence of eostnophilas," Joum. 

 Parasitol, 4, 1918, p. 135-7) has shown that the injection below the skin 

 of juices obtained from Hypoderma larvae whicli nourish themselves in 

 the subcutaneous tissues of suitable hosts, causes an eosinophiUa, tho- 

 eosinophils apparently playing an important part in neutralising toxins 

 from parasites. 



tWelsh and Chapman, Austr. Med. Gaz., 27, 1908, p. 1 (Human) ; 

 Weinberg and VeiUard, Sur lo diagnostic de rochinococcus chez le- 

 dromedaire, Bull. Soc. Med. Vet., 86, p. 50-1, Abstract in Jour. Trop,. 

 Vet. Sci., 4, 1909, p. 603 (Camel, sheep). 



JH. Zinsser, Infection and Resistance, 1918, pp. 86-7. 



**C. Marshall, Microbiology, 1917, p. G99. 



