TICK-RESISTANT CATTLE. 
Tick-Resistant Cattle: Mr. Munro Hull’s Claims. 
By T. HARVEY JOHNSTON, D.Sc,. and Miss M. J. BANCROFT, B.Sc., 
Biology Department, University, Brisbane. 
In September, 1912, Mr. G. W. Munro Hull, of Eumundi, North Coast Line, 
called attention to the existence of a tick-resisting condition in a certain number 
of the cows forming his dairy herd, such animals remaining free from tick infesta- 
tion, whilst the remainder were regularly attacked. He believed that this 
peculiarity was caused by the presence in such animals of some tick-destroying 
microbe, and that it was possible to convey the resistant quality to other animals 
by vaccination of the latter with some of the “lymph” occurring chiefly on the 
escutcheon of resistant animals. It was stated that such cows did not require 
to be sprayed or dipped since they remained sleek and clean-coated, whilst the 
untreated stock suffered from tick attacks. The vaccinated animals were liable 
to invasion by tick larvie, but the latter nearly always died soon afterwards. 
Only on rare occasions did any reach maturity and lay eggs, but such eggs had | 
not been found to hatch. Even when such animals were turned out into open 
country for months at a time, they maintained their resistance, whilst’:ordinary 
cattle under the same conditions became heavily infested, some dying of tick 
worry, even though food was abundant. Mr. Hull also suspected that the 
resistant condition was hereditarily transmitted. 
The Agricultural Department purchased two cows, Clover and Tinkerbell 
(specially selected by Mr. Hull as examples of his resistant stock), in order to 
test the correctness of these claims. Since the latter were more specifically stated 
by him at a later date, we might briefly summarize the list published as a parlia- 
mentary report in the latter part of 1914. 
(1) That these cattle never mature. more than a few odd female ticks during 
the course of a year—a total of from 50 to 100 per year being the highest 
estimate, though the animals are regularly infested (naturally) by myriads of 
larvie, the majority of which die while still very minute. 
(2) That as a result of such freedom from developing ticks, these cattle do 
not require any attention as regards ticks, and may be turned out on any country 
for indefinite periods without experiencing tick worry, and, consequently, present 
a clean, sleek appearance. 
(3) That this peculiarity is transmissible to other cattle by “contact” (i.e., 
natural infection) and by vaccination, and is transmitted in every case to the 
progeny of such animals, but does not manifest its presence in the offspring until 
after the first year of life. 
(4) That the material used for vaccination (i.e., the exudate occurring on the 
escutcheon of resistant stock) is not produced as a result of excessive tick worry. 
(5) That the comparatively few female ticks which are to be found maturing 
on such animals have become displaced without injury from other cattle, and 
have re-attached themselves to the resistant stock. 
(6) That though these ticks may lay eggs, no larve develop from them, 
though eggs laid by ticks taken from control cattle readily hatch. 
(7) That a few ticks are to be seen at odd times on resistant animals during 
winter when other cattle are free from them. : 
(8) That such animals have a markedly higher temperature than other cattle 
during winter. . 
In 1914 Mr. C. J. Pound, Director of the Yeerongpilly Experimental Station, as 
a result of his observations regarding the two cows purchased by the Government, 
reported adversely on Mr. Hull’s claims. He stated:— ' 
(1) That after having been placed in a ticky paddock for 27 days the two cows 
matured large numbers of ticks. 
(2) And that they became so badly infested and tick-worried that dipping or 
spraying would have been justified. ‘ 
(3) That he had not been able to transmit the alleged peculiarity to other 
cattle either by contact or by vaccination; while the calf of one of the two animals 
was commonly more or less heavily tick infested, 
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