USDA finalizes screwworm rule

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The Department of Agriculture has issued a final ruling requiring certain animals that are imported from regions of the world that have screwworms to be inspected and treated to prevent the pest from taking up residence in the United States. The final rule makes the interim regulation, which has been in effect since Nov. 13, 2000, permanent with only a few modifications.

Screwworms, which cause extensive damage to livestock and other warm-blooded animals, are native to tropical areas of South America, the Indian subcontinent, Southeast Asia, tropical and sub-Saharan Africa, and the Arabian peninsula. The pest was eradicated from the United States in 1996, but screwworm larvae were found in horses transported to the United States from South America in July 1999 and February and March 2000. The interim rule was put in place to prevent the introduction of screwworm into the United States.

Effective on its publication date, March 15, 2002, the final rule requires the inspection and, if necessary, treatment, of horses, ruminants, swine, and dogs that are imported from regions of the world where screwworms are thought to live. The interim rule was changed only slightly. The final rule allows male horses to be tranquilized or sedated, rather than anesthetized, so that veterinarians can examine the horses' external genitalia.

The rule can be found at or contact Dr. Glen Garris, Senior Staff Officer, Invasive Species Team, Animal Health Programs, VS, APHIS at (301) 734-8093.