IOO ECONOMIC MAMMALOGY 



to be disseminators in some localities. It will be recalled that not many 

 years ago this plague appeared at different times in New Orleans, Seattle 

 and San Francisco, and was checked by prompt, effective campaigns 

 against rats and in one case against ground squirrels also. In the San 

 Francisco campaign 278,000 rats were captured in four months and 

 it was estimated that 500,000 more were poisoned. 16 Lantz says that 

 the house rat is responsible for more deaths among human beings than 

 are all the wars of history, because of its relation to bubonic plague, 

 which in the fourteenth century destroyed from two-thirds to three- 

 fourths of the population of large areas in Europe 25,000,000 people 

 and since 1896 has killed 9,000,000 people in India alone, 1,200,000 

 in I9O7. 17 So active is the rat as a disseminator of plague that it has 

 been proposed to "build out the plague" by building out the rats through 

 the use of concrete, metal and the like in the construction of buildings. 18 



The spotted fever, or "tick fever," of the Rocky Mountain region, 

 especially virulent in portions of Wyoming, Montana and Idaho, rapidly 

 increasing in Colorado, is transmitted to human beings by the bites of 

 wood ticks which have become infected through first biting infected 

 mammals of some sort. The adult ticks have been found on mountain 

 goats, coyotes, badgers, wood rats, mice, woodchucks, snowshoe rab- 

 bits and bears, but are more frequently found on domestic stock; 19 

 hence many mammals aid in the spread of the disease by harboring 

 the ticks. Domestic sheep are excellent collectors of ticks, which easily 

 lodge in their wool. It has been thought by some that they could be used 

 effectively to collect the ticks and make possible their destruction by 

 frequently "dipping" the sheep. It does not seem to be very practicable, 

 as some of the most favorable localities for ticks are not favorable to 

 sheep and sheep cannot be long run in numbers over the same pasturage 

 used for cattle and horses. 20 



It is generally known that trichiniasis is transmitted to human be- 

 ings by means of under-cooked pork. The sleeping sickness in Africa 

 is transmitted from antelopes, dogs and monkeys to man by the tsetse 



16 Forbush, Rats and rat riddance, Massachusetts Board of Agric., Economic 

 Biol. Bull. No. i, 1915. 



17 Lantz, The house rat : The most destructive animal in the world, Yearbook 

 U. S. Dept. Agric. for 1917, pp. 235-251 ; The brown rat in the United States, U. S. 

 Biol. Surv. Bull. No. 33, 1909. See also Taylor, Science, XLVI, 124-125, 1917. 



18 Technical World Magazine, Nov., 1912, pp. 269-273. 



19 Birdseye, Some common mammals of western Montana in relation to agricul- 

 ture and spotted fever, U. S. Dept. Agric., Farmers' Bull. No. 484, 1912. 



20 See Wood, Experiments in the use of sheep in the eradication of the Rocky 

 Mountain spotted fever tick, U. S. Dept. Agric. Bull. 45, 1913. 



