New World Screwworm Fly
Cochliomyia hominivorax
Looking Beyond the Headlines
New World Screwworm is making headlines and causing concern. Here are some facts to help keep things in perspective.
Screwworm is a species of parasitic fly that is native to the Caribbean and Central and South America.
It was known to be in the southern part of the US by at least the mid-1800s and was a significant pest of livestock by the 1930s.
The United States, with the help of Mexico, began an eradication program using the sterile insect technique (SIT) starting in the 1950s
and successfully eradicated the screwworm from all of North America by 1966.
A Biological Barrier
Following eradication, a program for preventing screwworm populations moving north and re-infesting Mexico and the US was established at the 100 mile-wide isthmus of Panama called the Darién Gap. The focus of the program was to set up a biological barrier with constant releases of sterilized screwworms and regular monitoring. It worked, and screwworm populations have been held at bay ever since.
That is until around 2023 when the flies breached the barrier and isolated incidences of screwworm were reported in livestock in Mexico.
Why the breach?
Three factors:
Shipping infected animals north around the barrier, which means thorough inspections are needed to prevent this.
Interruptions in the release of sterile flies allowed for wild populations to move north. We need to maintain the SIT program. Diligence and consistency are key.
And climate change made for warmer winters in areas where weather would have otherwise helped to keep their populations in check.
The Screwworm Can Be Eradicated Again
The screwworm can be eradicated again with current technology, just as it was in Florida, 2016, when flies from isolated Caribbean Islands were carried aloft by the winds from Hurricane Matthew and blew into Florida. The flies were eradicated within just two months using sterile flies obtained from facilities in Mexico and Central America.
It was the first time in 30 years there was a screwworm outbreak in the US. The causes for which point us back to the need for continued surveillance in areas where the fly is still present and continuing eradication efforts where the fly populations are still high.
Wrap Up
The current situation does not warrant hyperbolic click-bait headlines about a deadly menace inching its way to the US. We already have the best tool for its eradication - SIT - which has proven effective every time.
What we do need is diligence in monitoring and maintaining the biological barrier approach.
So keep looking beyond the headlines to make sure you know the full story.
Sources
CDFA Screwworm Fact Sheet (trigger warning - gruesome photos)
Screwworm Eradication in the Americas
The Mexican-American Commission for the Eradication of the Screwworm