During the warm months, when screwworms 

 can establish themselves in the North and Mid- 

 west, livestock from those areas are inspected 

 to prevent screwwoi-m-infested animals from 

 entering the eradication area. Air, rail, and 

 ocean shipments of livestock also must be cer- 

 tified free of screwworms before they are per- 

 mitted to enter the eradication area. 



Durinjr the late summer and fall of 1958 and 

 1959 screwworms succeeded in establishing 

 themselves in several Mississippi counties ad- 

 joining the Mississippi River. Probably these 

 infestations were started by flies entering the 

 eradication area from Louisiana or Arkansas 

 under their own wing-power. The outbreaks 

 were controlled by intensive animal inspec- 

 tions, treatments, and State quarantines. 



Looking ahead in eradication 



The success of the eradication program in 

 the Southeast has stimulated considerable in- 

 terest among livestock growers and others in 

 the Southwestern United States. 



During 1959, a screwworm survey was made 

 in the Southwestern United States and North- 

 eastern Mexico to learn more about screwworm 

 habits and to evaluate the practicability of 

 using the sterile-fly technique in those ai"eas. 



The survey in Mexico failed to reveal any 

 natural barriers comparable to the water bar- 

 rier that encloses, on three sides, the screw- 

 worm overwintering area in Florida. An eradi- 



EAST-WEST LIVESTOCK MOVEMENTS 



Through Screwworm Inspection Stations 



THOUS 



75 

 50 

 25 

 



75 

 50 

 25 



MOVING EAST 



LiU 



mMmMR 



iluULuul 



MOVING WEST m 



iuuiiili 



UlUu 



1958 1959 I 1960 



& 0(MJI»[V Ciaa'CUlTJUt 



•WCULniatl. M tiucn Itovict 



cation eff'ort would not be practicable without 

 a perpetual program to prevent reinfestation 

 of the Southwestern United States through the 

 migration of screwworm flies northward from 

 Mexico. 



The vast territory involved, the climatologi- 

 cal and topographical differences from the 

 Southeastern United States, and the need for 

 additional information, indicate that any joint 

 United States-Mexican pi'ogram should first be 

 directed toward research, field trials, and meth- 

 ods development. 



CATTLE FEVER TICK 



A tale of ticks 



The theory is that cattle tick fever spread 

 to the Southern United States from the West 

 Indies and Mexico. The earliest report of the 

 disease in this country was made in 1796. In 

 the middle 19th century, there were frequent 

 reports of the infection in the South and South- 

 west. 



The nature of the disease was not under- 

 stood until 1889, when scientists of the U.S. 

 Department of Agriculture discovered that the 

 causative agent was a protozoan, Babesia bige- 

 niiua, transmitted by the cattle fever tick (Bo- 

 ophilus a)nnihif!is; and BoophilM^ microphts) . 

 The first step in control of the disease was to 

 quarantine the infested area. The order con- 

 trolling movement of southern cattle was is- 

 sued on July 3, 1889. 



By 1907, cattle tick fever (bovine piroplas- 

 mosis, Texas Fever, splenetic fever) was 

 prevalent in the Southern States, and had been 

 reported in California, Kentucky, Missouri, 

 Oklahoma, and Virginia. Except for a narrow 

 buifer zone along the Texas-Mexican border 

 and sporadic reinfestations in other places, the 

 Tick Eradication Program had eliminated fever 

 ticks from the United States by December 1943. 



All Mexican territory adjacent to the inter- 

 national boundary along the lower Rio Grande 

 River is tick infested. Reinfestations in Texas 

 by tick-infested Mexican animals illegally en- 

 tering the United States occur regularly. The 

 river boundarv is not an effective barrier 



20 



