Dog with screwworms brought to Mississippi

Published on October 15, 2007
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The Mississippi state veterinarian recently reported a case of screwworm infestation in a dog.

Private veterinarians in Mississippi found the fly larvae on a 16-year-old dog that was imported Sept. 13 from Trinidad. Dr. James A. Watson, Mississippi state veterinarian, said the U.S. Department of Agriculture's National Veterinary Diagnostic Laboratory confirmed the larvae to be Cochliomyia hominivorax—the New World screwworm.

The United States eradicated screwworms in the 1960s. Previously, the larvae had caused major economic losses to the U.S. livestock industry. One of the last reports of screwworm importation was in 2000, when a private veterinarian in Florida found C hominivorax larvae on horses from Argentina.

The Mississippi Board of Animal Health and the USDA Animal and Plant Health Inspection Service, Veterinary Services, performed an extensive investigation in response to the importation of screwworms on the dog. The traceback and the clinical presentation of the animal indicate a low risk for screwworm establishment in Mississippi.

Veterinarians should report screwworm infestations to state or federal authorities immediately upon diagnosis or suspicion of the disease. Contact information for federal area veterinarians in charge is at Information for state veterinarians is at

A fact sheet about screwworm myiasis is available from the Iowa State University Center for Food Security and Public Health at by clicking on Animal Disease Information, then on Factsheets.