LIVESTOCK PARASITOLOGY — SCHWARTZ 347 



named Piroplasma bigemima, were the causative agents of the disease, 

 and that the tick, Boophilus annulatus, merely served to transmit them. 



The determination of the nature of the causative agent of tick 

 fever and its mode of transmission, as well as the demonstration of 

 the main facts in the life cycle of the arthropod carrier, is certainly 

 among the outstanding achievements in microbiology. These dis- 

 coveries, significant as they were from a scientific standpoint, did not 

 by themselves ease the burden on livestock producers in the South, 

 whose cattle could not be shipped to northern markets, except for 

 slaughter, between the middle of February and the middle of Novem- 

 ber, in conformity with measures that had been adopted in the mean- 

 time to confine tick fever to the areas where it was enzootic. All 

 the Southern States, from Virginia to Florida, and extending west- 

 ward to include Texas and Oklahoma, were in the enzootic area. These 

 States, along with California, were sooner or later placed under 

 Federal quarantine. Therefore, to meet the practical needs of cattle 

 producers, and to afford relief to a large section of the country which 

 was seriously hampered in the development of a well-rounded agri- 

 cultural economy, it became necessary to devise means for freeing 

 cattle in the South and elsewhere of fever ticks. Investigations were 

 begun in 1892 in which many veterinarians outside the Bureau of 

 Animal Industry participated. These investigations were continued 

 for several years beyond the initiation, in 1906, of a systematic cam- 

 paign, under joint Federal and State auspices, with the objective of 

 eradicating cattle fever ticks from the United States. 



During a period of about 15 years various materials were tested as 

 smears, sprays, and dips for the destruction of cattle ticks, in an effort 

 to find a chemical that would destroy these arthropods without in- 

 juring their hosts. Substance after substance, as well as various com- 

 binations of substances, were tested and discarded, because the ticks 

 proved to resist them much better than the cattle. As a desperate 

 measure, cattle were even driven into the ocean's surf, in the hope 

 that the pounding of the waves would dislodge the ticks. By 1903 

 crude petroleum was generally accepted as superior to any other 

 tickicide discovered up to that time. Other control measures were 

 tried, including active and passive immunization of cattle against 

 piroplasmosis ; starving the ticks by removing the cattle from the 

 pastures contaminated with tick eggs and larvae, and keeping the 

 pastures vacant for several months ; and rotation of cattle on pastures, 

 based on the demonstrated facts in the life history of the arthropod 

 vector. These and other measures were tried as adjuncts to, or substi- 

 tutes for, dipping of cattle in medicated baths. 



In 1906 experiments were initiated with arsenical dips, which had 

 already been used in Australia and Cuba for tick eradication. Arsenic 



