348 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1952 



proved to be superior to any other tickicide that had been used up to 

 that time in this country. By dipping tick-infested cattle in arsenical 

 solutions every 2 weeks, which was the procedure finally adopted, 

 most of the ticks on the cattle were poisoned by the chemical. Hansom 

 determined that the engorged ticks which survived dipping laid fewer 

 eggs on the ground than those from untreated cattle. Of the larvae 

 that hatched from the eggs laid by the dipped female ticks, many died 

 before they could get onto cattle. The seed ticks which succeeded 

 in crawling onto cattle and living there were destroyed by the next dip- 

 ping in arsenic. In short, the cattle were used as the collectors of 

 the seed ticks present on the pasture, and the arsenical solution was 

 used to destroy them on the cattle. With successive dippings the 

 numbers of ticks found on cattle maintained on tick-infested pastures 

 gradually diminished and disappeared altogether after several months 

 of repeated dippings, at intervals of 2 weeks, throughout the spring, 

 summer, and early fall months. 



I have dwelt at considerable length on tick fever because it was 

 the first parasitic disease of livestock on which an all-out attack 

 was made in this country, with a successful outcome, and also be- 

 cause the story of tick fever in the United States is unparalleled in 

 the annals of disease control, human or animal, anywhere in the 

 world. With no definite knowledge whatsoever available in the be- 

 ginning as to the cause, or mode of transmission, of the disease, all 

 the facts pertaining to its nature and mode of spread— which cer- 

 tainly was a surprising one at the time it was made — and habits 

 and mode of life of its arthropod vector, were brought to light as 

 a result of research carried out in one place. Moreover, the means 

 whereby the vector could be destroyed, without unduly injuring the 

 host, also were discovered. This paved the way for cutting the 

 lifeline by means of which the piroplasms were carried from the 

 blood of one bovine to another. Finally, on the basis of the facts 

 ascertained through long-sustained experimentation, a death sen- 

 tence was pronounced on the two arthropod carriers of the disease, 

 Boophilus annulatus and Boophilus microplus, and on the sporozoan 

 parasites which they conveyed to their bovine hosts. That this sen- 

 tence was carried out after more than four decades of strenuous effort, 

 and in the face of strong opposition, is certainly a tribute to the re- 

 search workers who forged the weapons of tick destruction, and to the 

 many who used them. 



Cattle fever ticks and the disease they transmit have been eradi- 

 cated from the United States, except from a long, narrow strip of 

 territory adjacent to the Rio Grande River. This strip, which is 

 about 500 miles long, extends from Devils River near Del Rio, Tex., 

 to the Gulf of Mexico, and to an average depth of 4 to 5 miles. As 



