LIVESTOCK PARASITOLOGY — SCHWARTZ 349 



far as can be foreseen now, the cattle in this buffer zone will remain 

 under quarantine until fever ticks are eradicated from Mexico. De- 

 spite the systematic dipping of cattle in the buffer zone, the drifting 

 of animals from both sides of the river maintains the tick infesta- 

 tion, accompanied by occasional cases of piroplasmosis. 



SHEEP SCABIES 



At no time did scab or scabies of food-producing animals present 

 a challenge that was even remotely comparable to that presented 

 by the once mysterious malady called Texas fever. In 1884 the 

 cause of sheep scab was well known, as was also the life history of 

 the mite, Psoroptes equi var. ovis. The research that brought these 

 facts to light was done in the first half of the nineteenth century, 

 when it was shown by experiments that scabies in sheep did not 

 develop in the absence of mites, and could be produced experimentally 

 by transplanting the specific scab mites from affected to healthy 

 sheep. It had been established also that the losses from this disease 

 were severe, and resulted in the shedding of the wool, marked 

 emaciation, anemia, and exhaustion which finally ended in death of a 

 large percentage of untreated animals. 



Before the turn of the century sheep in large areas of this country 

 were affected with scabies, and many stockmen were forced to forsake 

 sheep raising on account of the ravages of this disease. In fact, so 

 severe were the monetary losses sustained by owners of scabby 

 flocks, that Salmon and Stiles in 1898 regarded this disease as second 

 only to hog cholera, from the standpoint of the loss of invested 

 capital in livestock raising. The large bands of sheep on the Great 

 Plains and in the Rocky Mountain region, as well as sheep in the 

 feeding centers farther east, were most severely affected. Moreover, 

 diseased sheep from those areas were sent to the large markets of 

 the country, thereby spreading scabies almost everywhere. As a 

 consequence of the uncontrolled marketing of scabby sheep, the stock- 

 yards became contaminated and many animals that were purchased 

 there were likely to develop the disease. 



Various plans were tried to arrest the further spread of scabies and 

 to devise means of eradicating it. In 1895 a decree was issued, pur- 

 suant to authority granted by the Congress, prohibiting scabby sheep 

 from entering stockyards or any other places where animals are 

 handled for interstate trade, or to enter into interstate trade, but no 

 apparent progress was made in checking the disease. Subsequent 

 orders required cleaning and disinfecting boats, railroad cars, and 

 other vehicles which had been used for the transportation of scabby 

 sheep ; prohibited railroads and other transportation companies, and 

 captains of steamboats, from receiving for transportation, or from 



