54 



THE ANIMAL PARASITES OF MAN 



[The chief wild hosts are the brown bear, coyote, woodchuck, 

 rabbit, wild cat, badger and mountain goat for the larvae ; practically 

 all small mammals act as hosts for larvae and nymphre, whilst the 

 adults are seldom found on other than large domestic animals ; horses 

 and cattle are preferred. It occurs in British Columbia, southward 

 to Northern New Mexico, and from the foothills of the Rocky 

 Mountains in Colorado to the base of the Cascade Range in Oregon 

 and California; abundant in Western Montana, Idaho, Eastern 

 Washington, Oregon, North Utah, West Wyoming and North-west 

 Colorado. 



[Of great importance in the Bitter Root Valley of Montana, where 

 a number of cases of fever occur each year, with a mortality of about 

 70 per cent. In British Columbia this tick causes tick paralysis in 

 man and sheep. Only the adults seem to attack man and animals 

 there (Hadwen and Nuttall, Parasitology, 1913, vi, No. 3, pp. 288- 

 297 and 298-301) according to the Canadian Medical Associa- 

 tion Journal, December, 1912. The symptoms are unlike spotted 

 fever. For full details of this tick vide Bulls. 105 and 106, U.S. 

 Dept. Agric.] 



Dermacentor occidentalis, Neumann. 



This tick only occurs in the Pacific Coast region of the United 

 States. Owing to the fact that it frequently attacks man as well as 

 occurring in great abundance in Oregon and California, it is of con- 

 siderable economic importance. It is spoken of as the wood tick, and 

 in the regions where found is the most common tick to attack man. 

 Hooker, Bishopp and Wood (Bull. 106, U.S. Dept. Agric., Div. Ent, 

 1912, p. 189) state that a number of cases have been brought to their 

 notice where the bite of this tick has caused considerable local inflam- 

 mation, which in some cases required physicians' attention. It has 

 been supposed to be connected with Rocky Mountain spotted fever, 

 but it is doubtful if it is concerned in its transmission. The engorged 

 female is steel grey, the dorsum with an olive-green surface colour, 

 which covers the grey except in small spots, giving a mottled 

 appearance. The unengorged males and females are reddish-brown, 

 scutum covered with a whitish bloom, interrupted by many red 

 punctures. The female is 9 by 6'i by 3-3 mm. to ir8 by 7-6 by 

 5-6 mm. ; the male 2-8 by r6 mm. to 4-2 by 2-3 mm. The larvae 

 are bluish-grey when engorged, reddish-brown when unengorged. 

 The nymph is light brown, sides of scutum darker, and the 

 intestines dark brown. It is confined to the Coast Range and 

 Sierra Nevada Mountains in California and Oregon and the small 

 mountain range to the south-west. 



