342 QUEENSLAND AGRICULTURAL JOURNAL. [1 Szpz., 1901. 
PROPHYLACTIC. 
We must look to a prophylactic to furnish the means of putting on the 
drag and combating the Rew malaria. 
In the etiology of this disorder, two inseparable factors play the principal 
part: the hematozoa and its intermediary. the tick. Whether we prevent the 
action of one or the other, the result is identical; the disease is prevented. We 
“ry shall, therefore, divide this chapter into two parts—one relating to ticks, the 
| other to hematozoa. 
1.—MEASURES AGAINST TICKS. 
I have endeavoured to point out the danger of travelling stock on foot in 
the infested zones. Not only is there a risk of a certain number dying, but the 
survivors may carry with them infectant ticks and thus create new homes of 
malaria in fields up to that time free. Especially when it is a question of 
transporting breeding cattle, should they, as much as possible, travel by train, 
a ‘and as a corollary, the trucks should be carefully cleaned and disinfected before 
ie being used for the transport of stock. In certain countries, no ticks, to speak 
of, are found in winter; that season, then, is the most favourable for moving stock. 
Jt has been tried, particularly in the United States and in Australia, to 
“hie destroy the ticks on animals destined for districts free from malaria, For this 
st purpose very ingenious dips have been used, but the results are not 
Be commensurate with the labour and expense entailed. 
ae It is practically impossible to destroy the ticks in the field. All that ean 
ae be done with advantage is to set fire to the grass from time to time, when it is 
too high and too dry for cattle to eat. 
“ae Since observation and experiment have shown that calves resist natural 
Oe infection and become immune, it has been sought to acclimatise these young 
animals in dangerous zones. Unfortunately, it is the very young calf which is 
particularly refractory, and it has need of its mother’s milk for its deyelop- 
ment. By sending away both, the difficulty is not met. 
= al On the other hand, a man does not easily reconcile himself to waiting 
hs eighteen months or two years for the complete development of a brood 
th animal before deriving any profit from it by the improvement of his herd. 
One means much extolled, and which might be of real service, consists in 
placing young ticks on sensitive animals, and thus conferring immunity on them, 
The breeding of ticks is very simple, so that the necessary number for 
this style of vaccination could easily be obtained. I have made several 
experiments to demonstrate the efficacy of this proceeding. Animals which 
had nourished a certain number of ticks have not had the disease, and 
subsequent inoculation has shown that they were quite immune. In the month 
of April of this year (1900) I sent into the infested districts a cross-bred 
Durham cow and her calf eight months old on which I had raised fiye genera- 
tions of ticks without a single mischance. These two animals have always 
remained in perfect health from the very commencement of my experiments, 
whilst a great number of beasts taken to the same locality died of malaria. 
Still, the artificial infection by ticks presents inconveniences which render 
it difficult of application. Not being able to control their virulence, one would 
sometimes induce the disease and even kill the animals, whilst in other cases 
the animals would not be sufficiently treated to render them immune. Jn fact, 
we can pile on the ticks at pleasure, but we cannot take them off as easily, and 
they might then create new homes of infection. On the other hand, one may 
avoid the ticks in an open affected district by sowing lucerne. 
This very advantageous practice labours also under a, serious disadvantage 
which I have pointed out, and that is the almost certain infection of the cattle 
raised in these lucerne fields, the moment they leave them, without ever having 
previously been subjected to the influence of ticks. I would strongly advise 
owners of lucerne fields to reserve a small portion of their holding fe native 
grasses, so as to allow the young animals to find ticks and subsequent 
immunity. 
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