TICK-RESISTANT CATTLE. 
eggs laid by ticks from resistant cattle, conveying “ something ” derived from 
such animals to those which they infest, and thereby setting up resistance. Our 
experiments were unsuccessful. We also failed to find in the exudate any 
organisms other than those whose presence resulted from contamination. In 
this we agree with Mr. Pound’s findings. Moreover, there are many. animals 
which have been on Mr. Hull’s property in company with resistant animals for 
periods varying from one to seven years without becoming resistant. 
We, however, believe that in most cases the condition is naturally acquired 
as a direct result of moderate, long-continued infestation, which causes the pro- 
duction of an anti-tick substance in the blood and other fluids of certain cattle. 
In other words, we believe that the tick actually inject minute quantities of a 
poison (tick poison), and this stimulates the blood (just as the injection of 
other foreign substances does) to manufacture an anti-tick substance which 
neutralizes the poison. We have found an anti-coagulin in the cattle tick, and it 
is known that similar poisons occur in several other ticks, which, on injection, 
give rise to various symptoms, but, if recovery occurs, then an immunity, or at 
least a resistance, follows. 
We think that habituation is a step towards such resistance, and that the 
condition is slowly acquired as a result of tick attack. Some cattle-owners 
assert that if animals remain undipped for a season then the animals will either 
‘lie of tick worry or else become resistant. This is, perhaps, correct, but in view 
of the greater probability, of the former event happening, we think that dipping, 
in conjunction with a rotation of paddocks, should be systematically carried out, 
in order to control the tick pest and assist in its eradication. 
Baudate-—Associated with tick resistance there may be an exudate (Hull’s 
claim ‘No. 4 in this report), which we have already described in the pages of the 
Queensland Agricultural Journal (May, 1918, p. 172). It consists of drops-of a 
clear yellow fluid, which appear on the skin in various parts of the body, neck, 
dewlap, butt of tail, and escutcheon, notably on the last-named, where it is more 
evident owing to the shortness of the hair. These drops become thick and sticky, 
ultimately forming little granular masses of thin, flat, yellow seabs, according to 
the size of the original drop. ‘The largest patches seen were about the size of a 
sixpence, or slightly larger. In some animals these little masses of exudate are 
perfectly clear, the skin appearing through them quite uninflamed. In others 
some blood may be present, and then the resulting scab is discoloured. When 
dry, these scabs are readily flaked off, leaving a rounded area of smooth, clean 
skin beneath. There is no positive evidence to prove that each patch of exudate 
is caused by the bite of a tick, though, occasionally larval ticks have been found 
attached to a dry scab, having become entangled in the sticky fluid. This exuda- 
tion of lymph must be due to one, or both, of two causes—(1) either a slight 
“mechanical injury to the tissue which, while not actually penetrating a blood 
capillary, allows an escape of lymph from the tissues—such might be caused by 
the larval tick inserting its rostrum, and then withdrawing it and going else- 
where; (2). or to an increase in the blood pressure, involving an extravasation 
of lymph from the capillaries. The formation of small, hard lumps on the flanks 
and in the vicinity of escutcheon and neck of resistant animals, upon the centre 
of which a patch of fresh exudate may or may not appear, would be accounted for 
by an increase in blood pressure, since when scored, blood flows very freely from 
such lumps. The affected area is rather irritable, the cows showing a desire to 
lick or rub the part. This exudation makes its appearance particularly during 
the warmer months (October to June), especially during the moist weather. 
The condition just described appears to graduate into a type of tick-sore, so 
far only noticed on resistant animals. The scab formed over such a tick sore 
consists of two very distinct parts—an outer ring of a clear yellow substance, 
apparently composed of exactly the same matter as that spoken of above, sur- 
rounding a dark blood-stained core, on the upper surface of which there is a pit 
where the mouth parts of a tick have been inserted; while very often the tick is 
still present. Development up to the adult stage occurs in such ticks, but the 
females are unable to bloat, and remain stunted, sickly-looking individuals, even- 
tually dropping off with the scab. The under surface of this hard black core, 
surrounding the rostrum of the tick, often contains pus. When such a seab is 
remoyed a corresponding ‘pit is seen in the skin of the beast. 
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