1 Dec., 1897. ] QUEENSLAND AGRICULTURAL JOURNAL. 475 
that young animals are practically insusceptible to a severe attack of fever 
after inoculation, it is advisable to inoculate only young bulls intended for tick 
districts, and reserve the older uninoculated animals for the Southern clean 
districts; morevver, I would also strongly recommend to all stockowners, in 
clean districts, to avail themselves of the present opportunity of systematically 
inoculating all their young stock at the time of branding, so that they may be 
rendered immune before ticks make their appearance. 
NOTES ON TICKS AND TICK FEVER. 
There are several important points to be remembered in connection with 
a primary and subsequent invasions of ticks among cattle in clean districts, 
viz :— 
(1) A primary gross tick-infection is more frequently accompanied by 
a heavy mortality, but the surviving animals are invariably immune 
to subsequent attacks ; 
(2) A primary slight invasion of ticks is rarely accompanied by losses, 
and only renders an exceedingly small percentage of animals 
immune to a subsequent gross infection ; : 
(8) Continued slight tick-infection always more or less tends to 
produce permanent immunity from subsequent gross tick-infection ; ’ 
(4) The virulence of an attack is largely influenced by the ages and 
sexes of the cattle attacked, the old animals, especially bulls, being 
more susceptible than young animals. 
These results are based upon several years’ practical experience and careful 
observation, not only in this colony, but also in the Southern States of North 
America and South Africa. y 
The following carefully ascertained facts are several out of many examples 
which illustrate the correctness of the above remarks :— 
1. Dr. Hunt’s experiments at Hughenden, and others carried out in 
America and South Africa, prove that a severe and sometimes a fatal attack 
of fever may be produced by placing a large number of ticks upon a susceptible 
animal. The mortality on some of the Gulf stations, on the Flinders and 
Norman Rivers, and amongst the dairy and other cattle in and around 
Townsville, was occasioned, practically speaking, by a sudden gross invasion 
of ticks. 
2. The historical Airdmillan outbreak of ticks was as follows :—About 
2,500 head of cattle, travelling from Highbury and Devoncourt Stations, 
brought ticks with them to the Airdmillan paddocks on the Lower Burdekin in 
the winter of 1895, All the animals were more or less slightly tick-infested, and 
remained so—apparently in good health—for several weeks. Quite suddenly 
in October, a few weeks later, conditions being favourable, the ticks increased 
at an alarming rate, and the cattle became grossly tick-infested, and in six 
weeks 1,400 died of tick fever, the remaining 1,100 being sent to the boiling- 
down works. 
3. As an illustration of (8), I may mention the cases of Gracemere and 
Mount Cornish. On both these places (the former for, perhaps, over twelve 
months, and the latter for over two years) the cattle have been slightly tick- 
infested, but_ remained perfectly healthy. At the present time, on both 
properties, the cattle in certain paddocks are daily becoming grossly tick- 
infested, but still there are no signs whatever of sickness, all the animals 
looking healthy and fat. 
4. All experiments conducted by placing ticks on cattle or by the direct’ 
inoculation of virulent blood prove that young animals are only slightly suscep- 
tible, fatal cases being extremely rare. On nearly all permanently tick-infested ° 
stations at the present time there are, comparatively speaking, no serviceable old 
bulls which have survived the primary gross infection. The removal of bulls 
from clean into tick-infested districts invariably results in a very heavy mortality 
amongst the older animals, while the young ones, especially weaners, survive. 
