S. Hadwen 
291 
Attempt to transmit the disease hy inoculation (1913). 
Lamb No. V. 
Date 
13 V. Inoculated subcutaneously with 20 c.c. of defibrinated blood taken from 
Lamb No. IV. 
13 v.-l VI. Lamb remained perfectly well; no effects from inoculation. 
Experimental inoculation ivitli mashed-iip ticks. 
19 V. Inoculated in two places along the back with mashed-up ticks : one engorged 
? from Lamb No. Ill and one engorged ? from Lamb No. IV; three 
unengorged ? s from Keremeos. 
1 VI. No bad effects of any . sort to date. 
Experiments loith guinea-pigs. 
13 V. Two guinea-pigs were inoculated along the back with a few drops of fluid 
from mashed-up ticks. 
31 V. No results of any sort up to date; guinea-pigs destroyed. 
14 V. Six guinea-pigs were inoculated intraperitoneally with 2 c.c. each of 
defibrinated blood from Lamb No. IV. 
14 V. Six guinea-pigs were inoculated subcutaneously with brain emulsion. 
31 V. No results up to date, when guinea-pigs were destroyed. 
Summary. 
“Tick paralysis” occurs in British Columbia and affects man, sheep, 
and probably other animals. The disease is caused by the bites of Derma- 
centor venustus Banks. It is usually of short duration, is benign in 
character, but occasionally it persists for long periods, and may terminate 
fatally. From an economic point of view, the disease is of some import¬ 
ance to the sheep industry. The causative agent has not been discovered, 
and the disease has not been reproduced by inoculation. The most 
likely hypothesis is that the tick injects a toxin which gives rise to 
symptoms appearing coincidentally with the complete engorgement of 
the tick. In three consecutive cases, experimentally produced by me 
in lambs, paralysis occurred six to seven days after the ticks were put 
on. In no case did I fail to produce paralysis through the agency of the 
tick bites. It has been proved that D. venustus usually bites sheep 
along the back-bone; possibly the point of attachment may have some 
bearing on the symptoms or severity of the case. It is probable that 
other species of ticks may produce a similar disease. No larvae or nymphs 
were encountered on sheep, and I have no records of their attacking man 
in British Columbia. 
I am indebted to Dr F. Torrance, Veterinary Director-General, for 
permission to publish this paper. 
