358 TICKS 



transmission of diseases tick bites are dangerous to man in a 

 number of ways. 



The wounds made by ticks, especially if the head is torn off in 

 a forcible removal of the parasite, are very likely to become 

 infected and result in inflamed sores or extensive ulcers, not in- 

 frequently ending in blood poisoning. The author, as the result, 

 of the bite of a tick in northern California (probably Dermacentor 

 occidentalis) , suffered from an ulcerating sore on his arm, over half 

 an inch in depth and three-fourths of an inch in diameter. Blood 

 poisoning set in early causing a very high temperature and great 

 pain in the arm, and it was only a timely return to civiHzation 

 and hospital care that saved his arm if not his life. Sanitary 

 removal of ticks and cleansing of the wounds, as described on 

 p. 367, would be well worth the consideration of every inhabitant 

 or traveller in a tick-infested country. 



Tick Paralysis. — More serious than the painful wound made 

 by ticks is a pecuUar paralyzing effect of tick bites, known as 

 tick paralysis. This occurs especially from tick bites on the back 

 of the neck or on the head; it affects the legs first, but spreads 

 forward in a few days to the arms and neck and may result in 

 death. Paralysis in man and animals from tick bites has been 

 reported from South Africa and AustraUa and in North America 

 from the parts of Oregon and British Columbia inhabited by the 

 spotted fever tick. Sheep are especially subject to tick paraly- 

 sis, to such an extent in British Columbia as to present a serious 

 problem. This peculiar effect of tick bites has been reproduced 

 experimentally in sheep in places where it has not been known 

 to occur normally, by allowing a spotted fever tick, Dermacentor 

 venustus (Fig. 156), to bite along the spinal column. The bites 

 of this tick are particularly likely to cause paralysis, though it is 

 not yet known whether this is because of an especially toxic 

 secretion produced by this species or because of its preference for 

 biting along the spinal cord or on the head. There has been 

 much controversy as to what really causes the paralysis, some 

 authors believing that it is due to a microorganism injected by 

 the tick, since it is usually six or seven days after the attach- 

 ment of the tick before the effect is felt. The fact, however, 

 that no such organism can be discovered, that inoculations of 

 blood and other parts of diseased animals into healthy ones does 

 not result in transmission of the disease, and that the paralysis 



