Tag Archive: Screwworm

APHIS Confirms New World Screwworm in Dade County Dog

APHIS Confirms New World Screwworm in Dade County Dog


Screwworm larvae. Source: Foreign Animal Diseases “The Grey Book” USAHA

The United States Department of Agriculture’s (USDA) Animal and Plant Health Inspection Service (APHIS) confirmed the presence of New World screwworm (Cochliomyia hominivorax) in a stray dog near Homestead, Florida. The dog was isolated and his infested wounds were treated. Federal and state officials have started active surveillance in the area.

This is the first confirmed case on Florida’s mainland. Screwworm was first confirmed on October 3, 2016 in Key deer from National Key Deer Refuge on Big Pine Key, Florida. This initial presence of screwworm was the first local detection in the United States in more than 30 years and Florida’s Commissioner of Agriculture, Adam Putnam declared an agricultural state of emergency in Monroe County, Florida.

Since October, 13 Keys had known infestations mostly in the key deer population, with five confirmed infestations in domestic animals. Animal health and wildlife officials at the state and federal levels have been working aggressively to eradicate this pest. Extensive response efforts have included fly assessments to determine the extent of the infestation, release of sterile flies to prevent reproduction and disease surveillance to look for additional cases in animals. Officials have received significantly fewer reports of adult screwworm flies in the area and fewer cases of infected Key deer. To date, fly assessments have been conducted on 40 Keys. USDA has released over 80 million sterile flies from 25 ground release sites on twelve islands and the city of Marathon. The initial epidemiology report on the Florida Keys infestation may be viewed at https://www.aphis.usda.gov/stakeholders/downloads/2017/nws-epi-report.pdf.

Life cycle of New World Screwworm from Fernandez and White, 2010. Investigation into Introduction of New World Screwworm into Florida Keys

Residents who have warm-blooded animals (pets, livestock, etc.) should watch their animals carefully. Florida residents should report any potential cases to 1-800-HELP-FLA (1-800-435-7352) or non-Florida residents should call (850) 410-3800.  Visitors to the area should ensure any pets that are with them are also checked, in order to prevent the spread of this infestation.

While human cases of New World screwworm are rare, they have occurred, and public health officials are involved in the response. No human cases have been reported in Florida. For more information about this disease in humans, please contact your local public health department. Using fly repellents and keeping skin wounds clean and protected from flies can help prevent infection with screwworm in both people and animals.

New World screwworm are fly larvae (maggots) that can infest livestock and other warm-blooded animals, including people. They most often enter an animal through an open wound and feed on the animal’s living flesh. While they can fly much farther under ideal conditions, adult flies generally do not travel more than a couple of miles if there are suitable host animals in the area. New World screwworm is more likely to spread long distances when infested animals move to new areas and carry the pest there.

In the 1950s, USDA developed a new method to help eradicate screwworm using a form of biological control, called the sterile insect technique, which releases infertile flies in infested areas. When they mate with wild females, no offspring result. With fewer fertile mates available in each succeeding generation, the fly, in essence, breeds itself out of existence.  USDA used this technique to eradicate screwworm from the U.S. and worked with other countries in Central America and the Caribbean to eradicate it there as well. Today, USDA and its partners maintain a permanent sterile fly barrier at the Darien Gap between Panama and Colombia to prevent the establishment of any screwworm flies that enter from South America.

For more information on this subject, use the following links:

USDA Confirms Screwworms in the Florida Keys

Investigation into Introduction of New World Screwworm into Florida Keys

APHIS New World Screwworm Fact-sheet



Author: admin – webmaster@ifas.ufl.edu


Permanent link to this article: http://franklin.ifas.ufl.edu/newsletters/2017/01/13/aphis-confirms-new-world-screwworm-in-dade-county-dog/

New World Screwworm: Gone -Yes, but not Forgotten!

New World Screwworm: Gone -Yes, but not Forgotten!


Florida has a long history with New World Screwworm.  Shown here from the left, is a screwworm fly and screwworm larvae (or maggots).

Several kinds of maggots infest the wounds of warm-blooded animals; however, the only one that feeds exclusively on live flesh is the screwworm, and Florida has a long history with New World Screwworm (Cochliomyia hominivorax).  The adult flies of these flesh eating maggots migrated from central and south America to parts of the United States, and were common in Florida during the early to mid-1900s.  Screwworm-related cattle producer losses in the southeastern United States were estimated at $ 20 million per year in the 1950s (imagine the cost in today’s economy!).  Beginning in 1958, a coordinated, two-year, state-federal eradication program began in the southeastern United States.  Even though these efforts eradicated the screwworm fly from the Southeast; there is constant danger of re-infestation.  In Florida, we continue to see screwworm in imported animals.  Since 2000, 12 imported animals with screwworm larvae infestations were identified in Florida.  The larvae were eliminated before the fly could become established, but awareness and constant surveillance is the only way to prevent reintroductions of this pest into the United States (http://www.flsart.org/screwworm/index.jsp).

Screwworm infestation

Screwworm infestation

The Florida Department of Agriculture and Consumer Services (FDACS), Division of Animal Industry, the Florida State Emergency Operations Center (SEOC), and the Florida State Agricultural Response Team, have conducted first response training and provide educational materials to increase awareness about this and many other pests, disasters, and diseases that can affect Florida’s agriculture.

Anyone suspecting a screwworm infestation is urged to immediately contact:

Your local UF/IFAS County Extension Director

A local veterinarian

State Veterinarian’s Office
Florida Department of Agriculture and Consumer Services
Division of Animal Industry
8:00 a.m. – 5:00 p.m. (850) 410-0900
After hours: 800-342-5869
Email: rad@freshfromflorida.com

A website on the biology and distribution of the New World Screwworm, past eradication efforts, current eradication efforts, videos, and pictures, can be viewed at http://www.flsart.org/screwworm/information.jsp.

Further information about cattle parasites can be found in the following publication: External Parasites on Beef Cattle



Author: Judy Ludlow – judy.ludlow@ufl.edu

Judy Ludlow is the Agriculture and Natural Resource Agent in Calhoun County, Florida

Judy Ludlow

Permanent link to this article: http://franklin.ifas.ufl.edu/newsletters/2013/02/08/new-world-screwworm-gone-yes-but-not-forgotten/