N-28349 



Airplane releasing carton of sterile flies. 



The greatest numbers of sterile flies were 

 dispersed in tiie most heavily infested areas 

 and lesser numbers in the lightly infested 

 areas. Federal and State livestock inspectors 

 throughout the Southeastern States examined 

 livestock and maintained close cooperation 

 with livestock owners to determine the inci- 

 dence and relative abundance of screwworms. 



The native screwworm population gradually 

 declined, and by the end of 1958 screwworms 

 could be found only in Broward and Dade 

 Counties, Florida, where a localized infestation 

 persisted. This pocket of screwworms was 

 finally eliminated. The last case in the region 

 was found and destroyed February 19, 1959. 

 The only infestation that has been found in 

 Florida since that date was in a dehorning 

 wound, in Highlands County, on June 17, 1959. 



Challenge and termination 



The apparent absence of screwworms in 

 Florida for several weeks prompted program 

 officials to test the effectiveness of the eradica- 

 tion effort by discontinuing release of sterile 

 flies in a large part of the formerly infested 

 area. Accordingly, in mid-July 1959, release of 

 sterile flies was discontinued in that portion 

 of Florida south of an east-west line through 

 Lake Okeechobee. The number of livestock 

 inspectors in the untreated area was doubled. 



and livestock owners were urged to make fre- 

 quent inspections and promptly report any evi- 

 dence of screwworms. When no infestations 

 were reported in the test area in the ensuing 

 3 months, rearing and release of sterile flies 

 were progressively diminished in the remainder 

 of the Southeast. 



Screwworm fly rearing operations ceased, 

 and the last sterile flies were dispersed on No- 

 vember 14, 1959. The building then was sealed 

 and sprayed with an activated pyrethrin insec- 

 ticide, and on the following day fumigated with 

 DDVP and TEPP. These precautions were 

 taken to ensure destruction of any fertile 

 screwworm flies tliat might escape from the 

 heretofor fly-secure building and repopulate 

 the area. The establishment was then placed 

 on a standby basis to remain available for 

 emergency use. 



Continuous alert 



Continuing systematic animal inspections 

 for evidence of screwworms, and trapping and 

 identification of flies in areas over which sterile 

 flies had been released, ensured rapid detection 

 of wild flies or larvae that might .still survive 

 in the eradication area. 



An insurance screwworm colony is main- 

 tained at a Department laboratory in Texas. 

 Stock from this parent colony could be used in 

 an emergency to combat future localized out- 

 breaks. 



During and following eradication efforts in 

 the Southeast, it has been necessary to guard 

 rigidly against reintroduction of screwworms 

 on animals moving interstate from the screw- 

 worm-infested Southwest. This protection has 

 come, through Federal regulation, from the 

 establishment of 13 livestock inspection sta- 

 tions along the eastern borders of Arkansas 

 and Louisiana. 



All livestock entering the Southeast from the 

 Southwest must be unloaded and inspected at 

 one of the stations. All wounds on livestock are 

 treated with an approved smear. This is fol- 

 lowed by thorough application of an organic 

 phosphorus insecticide to all animals except 

 those specifically exempted. A number of 

 screwworm-infested animals have been inter- 

 cepted and treated at these stations before be- 

 ing permitted to enter the Southeast. 



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