Following the recent outbreak of screwworm flies in Florida, the USDA’s Animal and Plant Health Inspection Service's (APHIS) Veterinary Services (VS) program has released an environmental assessment of its plans for preventing and eradicating future outbreaks.

Screwworms are extremely destructive parasites in livestock and wildlife, causing severe discomfort, lost performance and deaths. Historically, screwworms plagued livestock operations in the southern United States until the 1960s, when the UDSA led an eradication effort using the new “sterile insect” technique. The USDA interactive website illustrates the biology of the screwworm fly and uses maps to illustrate past and present eradication efforts.

The United States was declared screwworm-free in 1966, followed by Mexico in 1991, Belize and Guatemala in 1994, El Salvador in 1995, and Honduras in 1996. The outbreak in the Florida Keys, which began during the summer of 2016, was the first Florida infestation in 57 years and the first U.S. infestation in 34 years. The outbreak mostly affected the rare Key Deer, and between October 2016 and January 2017, more than 130 Key deer were killed by screwworm or had to be euthanized as a result of screwworm

The USDA and Florida animal-health officials acted quickly, releasing millions of sterile flies and using oral ivermectin, and were able to declare the screwworm once attain eradicated in March 2017.

Under USDA’s preferred plan, a cooperative screwworm eradication program would be “characterized by a comprehensive program to detect screwworm flies in all life stages, treat infested individuals, and, where necessary, release sterile screwworm flies.” The program would involve the cooperation of APHIS with State and local agencies and departments to eliminate any potential pest risk when emergency program action is necessary. The plan emphasizes prevention of introduction and spread of the parasite, at significantly lower costs compared with controlling outbreaks in the absence of this effort.

The Environmental Assessment  analyzes the potential environmental impacts of alternatives for APHIS' involvement in screwworm eradication.

APHIS is seeking public review and comment on the EA. Interested parties may obtain the EA at, Cooperative Screwworm Eradication Program Draft EA or by submitting a written request to USDA-APHIS-Veterinary Services, Cattle Fever Tick Eradication Program, 2150 Centre Avenue Building B, Fort Collins, CO 80526. Requests for the EA may also be sent via email to

Consideration will be given to all comments received by September 25, 2017. Send two copies of postal mail or commercial delivery comments to:

Docket No. APHIS-2017-0068
APHIS Regulatory Analysis and Development—PPD 4700
River Road, Unit 118, Station 3A-03.8
Riverdale, MD 20737-1238

If you wish to submit a comment using the Internet, you may do so through the Federal eRulemaking portal at