1 June, 1902.] QUEENSLAND AGRICULTURAL JOURNAL. 485 | 
TEXAS OR TICK FEVER. 
Some Interesting ExpEriences. 
The sixteenth annual report of the Bureau of Animal Industry, Washington, 
United States, America, lately to hand, contains some reports of continued 
experiments by Dr. Shroeder, the Superintendent of the Experiment Station, 
which possess great interest to the cattle-owners of this State. Dr. Shroeder 
conducted a series of experiments in the growing of non-infected ticks, and 
afterwards infected them. An effort was made to grow ticks on animals 
refractory to Texas fever. Horses, mules, dogs, sheep, goats, rabbits, guinea 
pigs, and pigeons were used, but the ticks persistently refused to take hold of 
and grow upon any of the animals named. He has since been assured, 
however, that they occasionally grow on horses and mules in the Southern 
States. He determined to see what could be done by using very young calves, 
which are practically immune from Texas fever. All his experiments are given 
in detail, but here it will only be necessary to state that ticks from cows 
obtained from the fevered regions of the Southern States were placed on two 
very young calves when they matured; they were placed in a bottle, the mouth 
of which was plugged with cotton wool, where they deposited their ova, and the 
latter hatched in due course. The young ticks were placed on a cow and calf, 
and were found not to produce the disease. Ticks collected from the cow and 
subsequent generations of those ticks, were all found to be non-infectious. It 
was found, however, that whenever any of these ticks were placed on cows from 
the Southern States that had passed through the fever and had the organisms 
in their blood, they became pathogenic, their progeny never failing to produce 
Texas fever when placed on northern susceptible cattle. 
During these experiments an important discovery was made—namely, that 
it is possible to carry infection by means of insects other than ticks from an 
infected to « susceptible animal. Two cases of the kind are stated by Dr. 
Shroeder. In a field where the clean cattle were kept, and separated from the 
infected paddock by a ditch and two lines of fence, a cow was found to be 
suffering from Texas fever, although no ticks were found on her, nor on any of 
the other cattle in the same field. A second case, a cow, had received a 
hyperdermic injection of blood from a southern cow, and died from its effects. 
A fly caught on her body was found to have its abdomen distended with blood. 
This blood was pressed out on a slide, and examined under the miscroscope, 
and was seen to contain many almost perfect corpuscles, nearly every one of 
which was infected with a large Texas fever parasite. Eleven days after the 
death of this cow another cow in the same enclosure was observed to be passing 
bloody urine, and she died nineteen days after the symptoms were first observed. 
No ticks were found on her, nor on any of the cattle in the same field. The 
case was one of true Texas fever, and from these two cases the doctor thinks it 
is reasonable to assume that flies, and possibly other blood-sucking insects and 
external parasites, may carry infection from one animal to another; but he 
thinks the case must be very rare, and that no general outbreak can be produced 
in this manner. 
On the vitality of the cattle tick he records an instance in which he placed 
a number of female ticks in a cotton-stoppered flask, and kept them in a warm 
room. ‘The time which elapsed from the day the adult ticks were collected until 
the day when a host was provided for the young ticks was 168 days, or very 
nearly the half of the year. Dealing with the persistence of the Texas fever 
organism in the blood of cattle, he cites an experiment of two calves, from four 
to five months old, which received a hyperdermic injection of blood drawn from 
the jugular vein of two southern cows. One was inoculated with blood from the 
North Carolina cow, whose cases have been so often cited. She arrived at the 
experiment station in 1889, and her blood is still virulent. The two calves 
suffered an attack of Texas fever, so mild in character thatit would have escaped. 
notice without careful examination of the blood. The blood of those calves was 
afterwards injected into two northern cows, both of which passed through a 
