Screwworm and the Key Deer

at National Key Deer Refuge
Key deer with blue paint

The U.S. Fish and Wildlife Service (Service) is working with the citizens of the Florida Keys to respond to the screwworm infestation with an "all hands on board" approach.  The Service has deployed dozens of biologists, veterinarian, outreach specialists and other employees to the Keys and has trained over 120 local citizens to help administer doses of anti-parasitic medication to Key deer.  The Service is not limiting the methods being used in this effort and is constantly exploring more effective scientific avenues to protect Key deer from this parasitic insect. 

There were only about 1,000 Key deer left in the world.  Biologists estimate that this screwworm outbreak has eliminated about 10 percent of them.  Responding to this infestation is a top priority for the Service.  Fortunately, since biologists, veterinarians and trained volunteers started administering doses of an anti-parasitic drug to the Key deer, it appears that the number of minor to moderately infested deer and the number of severely infested deer that need to be euthanized is down.

The endangered Key deer is the smallest subspecies of the North American white-tailed deer.  They only inhabit 20-25 islands in the lower Florida Keys.  All ages and sexes of Key deer can be infested by screwworms.  However, we are mainly seeing males, or bucks, who are infested as a result from injuries caused by fighting with other males during the mating season. 

For more information on screwworm and this outbreak, please visit the Florida Department of Agriculture and Consumer Services' website or see this U.S. Department of Agriculture Fact Sheet.  

What is the U.S. Fish & Wildlife Service doing to help?

Service staff and trained volunteers are administering medicine to the Key deer called Doramectin, an anti-parasitic that should prevent screwworm infestations as well as treat deer with minor to moderate infections.  Biologists administer doses to Key deer with bread that has been injected with Doramectin, and mark each animal with non-toxic paint to indicate it has received treatment.  We are involving citizen scientists by using a neighborhood blitz approach, targeting a different area each day to ensure we reach as many deer as possible without over-medicating any.  Deer must receive a dose every 7 days for the medicine to be effective.  For the latest number of treated deer, please visit our Facebook page or see the notice on our home page

As concerned citizens and visitors report potentially infested deer to the Key Deer Hotline, first responders locate and evaluate the Key deer to determine if veterinarian care may be able to increase their chances of survival.  If the infestation is mild to moderate, veterinarians may be able to successfully provide care. Experienced veterinarians sedate the deer with a dart. Veterinarians care for the wound and give deer antibiotics and fluids. Key deer are functioning within 20-30 minutes after waking up.  To determine how effective this care is, the veterinarians place a yellow plastic tag on one of their antlers and shave a number into the fur on their side.

Unfortunately, some Key deer reported to the Key Deer Hotline are so badly infested that they cannot be effectively treated or rehabilitated.  Therefore, we must euthanize some animals to humanely end their suffering.  Otherwise, the extent of the injuries caused by the maggots will ultimately lead to a slow, painful death. 

 The Service is also acting on a contingency plan to build and use temporary enclosures to isolate small groups of Key deer in order to ensure the survival of the species.  Two temporary enclosures located on Big Pine Key and Cudjoe Key will act as a potential temporary ark for endangered Key deer, and will only be used if the population shrinks below a size suitable for survival. Biologists hope the situation never deteriorates to the point of warranting the temporary enclosure, but are preparing for the all possibilities.

Screwworms can be controlled in the wild, although the process takes time.  To learn how the U.S. Department of Agriculture plans to eradicate screwworms in the Florida Keys, please visit their website.  

How can you help?

  There are a number of things you can do to help.   

  • Help us spread the word about this infestation.  
  • Report any suspected infected deer to the Key Deer Hotline at 888-404-3922 ext. 7.  Once a call is received, the Hotline operator immediately contacts Refuge law enforcement staff who are on call 24 hours a day.  Staff will respond as quickly as possible - our goal is to respond within 10 minutes.  Once they are able to locate the deer, they will conduct a health assessment to determine the extent of the injuries or infestations, and decide if veterinary care is possible.  
  • Please drive carefully.  Key deer are in the middle of the rut, or mating season, and driven by hormones and instinct, they are interacting by fighting, mating and generally running around without much concern for traffic.  
  • Please do not feed Key deer, even though you may see biologists and trained Refuge volunteers feeding deer the medicated bread.  Attracting large numbers to feeding stations can lead to fights between deer, causing wounds that are susceptible to screwworm.  Deer congregating in groups may also promote the spread of this infestation and other diseases.  It is unlawful to feed Key deer.

You can also volunteer to help refuge staff administer doses of medication to the deer.  If you want to volunteer and are willing to participate in a training session, please contact Kristie Killam at

How can you get more information?

You can reach us at with any questions you may have.  We will also post updates as frequently as they are available on our Facebook page and the home page of this website.


Facts About Screwworm and the Key Deer

On September 30, 2016, New World screwworm was confirmed in the Key deer population on Florida's Big Pine Key.  The National Key Deer refuge is working with international, Federal, state and local authorities to eradicate the New World screwworm from the lower Florida Keys.

For the most updated information on the infestation and our efforts to control it, please visit our Facebook page