404 QUEENSLAND AGRICULTURAL JOURNAL. [1 Nov., 1897. 
Inoculation for Tick Fever. 
THE PROSPECTS AND PROBLEMS. 
By J. SIDNEY HUNT, M.R.C.S. 
“ Waar are the prospects of our being able to protect our cattle from tick 
fever by inoculation ?”’ ‘“ Have the experiments made in this direction been 
successful?’ ‘Is the evidence yet sufficient to warrant us in forthwith 
. inoculating our herds?” 
These are questions which are being anxiously discussed on all sides 
amongst stockowners. Unfortunately, they can none of them be answered 
in a sentence. And for this reason it is hoped that a brief survey of some of 
their more important features will not be unacceptable to those interested. 
What are our grounds, then, for thinking that inoculation of any kind 
will be protective against tick fever? In the first place, we have abundant 
evidence that cattle that have survived prolonged exposure to. virulent tick 
infestment*® become possessed of a power of resistance to the fever much 
ereater than that of normal cattle. This is a familiar observation in respect to 
the cattle in the permanently infested areas of the United States, and, in 
perhaps a less marked degree, to the cattle on Queensland runs through which 
the disease has already passed. If no such increased resistance were acquired 
in cattle perpetually exposed to ticks, it is evident that the herds, in all per- 
manently infested places, must, eventually, be exterminated. And we know 
that the very opposite of this is actually the case. In the permanently 
infested Southern States of America, cattle-raising is now a more important 
industry than ever. There is practically no mortality from tick fever; and 
the disabilities suffered by the industry from the presence of these parasites 
are confined to the difficulties of marketing the cattle into clean areas, and of 
importing high-class animals for the improvement of southern herds. More- 
over, in the case of Queensland cattle, increasing experience is steadily adding 
to our confidence that a like increased resistance succeeds the first disastrous 
waves of the specific fever which, sooner or later, follows in the wake of recent 
tick infestment. 
This increased resistance is often, for convenience, spoken of as 
immunity. It should be, at once, indicated, however, that by “immunity,” in 
this connection, is meant only such a degree of increased resistance as to 
amount to practical immunity under ordinary conditions. It is perhaps open to 
question if absolute immunity is ever acquired by cattle against tick fever, 
For it isa common observation in Queensland that herds through which the 
disease has passed may, though still tick-infested, he perfectly healthy on their 
own runs. Yet when such cattle are subjected to the hardships of droving, 
especially in bad seasons, a certain percentage will sometimes succumb to the 
disease. Unfortunately, we do not, in fact, know whether such mortality 
occurs in consequence of fresh tick infection, picked up on the stock routes, 
and affects only such animals as have, for some reason, previously escaped the 
disease, or whether it is in reality due to a second attack of fever, brought 
about by fresh tick infection in animals that have, indeed, already had the 
disease, but have not thereby acquired the necessary degree of resistance to 
withstand a fresh infection under the trying conditions frequently encountered 
on the stock routes. Or, again, for all we know to the contrary, the mortality 
* By “virulent tick infestment” is meant tick infestment which in any given place is known 
to be accompanied by acute tick fever. 
++ Immune cattle are to-day of greater selling value than susceptible ones. And, as Herbert 
Spencer points out, there is no surer test of such matters than the commercial test, | 
