NWS larvae. - - Screwworm Emergency Centre for North Africa (SECNA). In 1989 the Food and Agriculture Organization of the United Nations confirmed the presence of New World Screwworm (NWS), Cochliomyia hominivorax Coquerel, in Libya. It was the first incidence of screwworm outside the Americas, where it is considered the major livestock pest. The fly lays eggs on animal wounds as small as a tick bite. Within 24 hours, larvae hatch and begin eating their way into the wound. During the larval stage, NWS must feed on living tissue. As the wound is enlarged, more flies are attracted and the wound becomes re-infested. Unless treated, the host will eventually die. Fully grown cattle can die within ten days. On 15 June 1989, the Director-General of FAO established SECNA as an emergency programme charged with implementing an eradication programme based on the Sterile Insect Technique (SIT). This method of pest control depends on the release of millions of sterile flies which mate with the wild flies to produce sterile (dead) egg masses and breed the population out of existence. SIT is conducted in con-junction with a number of other activities such as an extensive programme of animal surveillance and treatment, a quarantine/inspection operation and detailed field research. Through the successful implementation of this programme and with widespread financial support, SECNA has been able to clear the infestation in Libya. The last wound infestation (myiasis case) was detected on 7 April 1991. Sterile fly release ended six months later on 16 October after the dispersal of more than 1300 million sterile flies in Libya. Surveillance activities are continuing to ensure NWS has not survived in some isolated cases.