USDA is reporting a case of new world screwworm (Cochliomyia hominivorax) in Mississippi in a dog imported from Trinidad and Tobago. This is the first occurrence of screwworm in the U.S. since 1982. All warm-blooded animals including humans are susceptible to screwworm infestation.
The history of screwworm control and eradication has a long and largely successful history which I find quite interesting. The screwworm was first identified in the southeastern U.S. in 1933. It survives in tropical and semitropical regions and is easily killed by freezing temperatures. A unique method of eradication was developed utilizing sterile male screwworm flies. Once released, the sexually sterile male flies mate with native females producing unfertilized eggs thus breaking the life cycle. The sterile male flies are released at a proportion of 300 sterile male flies per native male screwworm fly in a local area.
Eradication of the screwworm from the southeastern U.S. began in 1959 aided by a colder than usual winter that pushed the pest to the southern half of the Florida peninsula. Eradication from the southeast was achieved in 1961. A similar eradication effort was undertaken in the southwestern U.S. in 1962. Eradication from the contiguous U.S. was achieved in 1964.
Recognizing that the border with Mexico posed a potential route of reinfestation, a buffer zone was established along the entire Mexico-U.S. border and maintained from 1965 to 1981. In 1972, the two countries signed an agreement to establish a joint commission to eradicate the pest from Mexico. The eradication program began in 1976 and Mexico was declared free in 1991.
The movement of cattle from Central America into Mexico continued to pose a significant risk of reinfestation. The U.S. entered into agreements with Central American countries beginning in 1986 with Guatemala and ending with Panama in 1994. A permanent barrier was established at the Isthmus of Panama to prevent reinfestation to the north. The pest has been eradicated as far south as Honduras.
I realize this doesn’t have anything to do with swine medicine necessarily but I find it a very interesting and historically important international project that exhibits the kind of cooperation that can lead to a successful global eradication program.
Interestingly, I hear comments today in some circles questioning why U.S. livestock interests should participate in disease eradication programs internationally such as the effort to eradicate FMD in South America and the whole of the western hemisphere by 2010. Opponents of these efforts argue that eradication of these diseases internationally could harm export opportunities for U.S. agricultural products. In my opinion, as long as these diseases exist our industries are at risk. The potential losses associated with the introduction of a foreign animal, or transboundary, disease into the U.S. far outweighs the possible loss associated with increased competition in the international market. Our products can successfully compete internationally based solely on their quality, cost and safety and can only be enhanced in the absence of these devastating diseases.
As always, I welcome your thoughts and comments (email: comments@aasv.org).
Reference:
Foreign Animal Disease “The Gray Book”, US Animal Health Association & the University of Georgia College of Veterinary Medicine.