Carnivorous parasites are spreading through Mexico and Central America, raising concerns in the US, but officials have implemented several key measures just in case they reach here.
A June report from the USDA’s Animal and Plant Health Inspection Service (APHIS) discusses the New World Screwworm (NWS), a type of fly larva that inflicts a painful condition called myiasis on warm-blooded animals, including people.
The CDC clarifies that this term relates to the feeding habits of these larvae, often referred to as maggots.
When NWS infestations occur, a sharp mouth hook can cause significant damage to the host’s tissue. As more larvae emerge and feed, the injury can worsen considerably.
The USDA warns that if left untreated, these infestations in the Northwest could be fatal.
Where are the screwworms in the new world now?
Currently, the NWS is found in nearly all of South America, except for Chile, and in certain areas of the Caribbean.
Reports indicate a notable spike in NWS cases in Panama this year, prompting the parasite’s spread into Central America and potentially moving northward.
By November 2024, the NWS had reached southern Mexico.
As of the June report, the USDA indicated that NWS had not yet been detected in the US.
What is being done to prevent New World screwworms from entering the United States?
Authorities have a couple of strategies to mitigate the spread of NWS within the US.
One approach involves reducing contact between NWS flies and non-infected animals—this includes treating wounds on healthy hosts and isolating infected livestock.
Another method focuses on halting the species’ reproduction cycle altogether.
This can be achieved through the identification and treatment of infected animals, alongside utilizing sterile insect technology (SIT).
This technique involves exposing NWS pupae to gamma radiation, producing sterile flies that are then released to mate with females, resulting in the laying of non-viable eggs.
According to reports, the NWS population declined significantly, largely because females tend to mate only once in their lives.
How will it spread?
The invasion of NWS starts when females lay eggs in open wounds or other exposed areas, primarily affecting livestock but also posing risks to birds and humans.
Female flies are drawn to the scent of wounds, and even tiny scratches can attract them.
A single female can deposit between 200 and 300 eggs at once and might lay as many as 3,000 throughout her lifespan, which ranges from 10 to 30 days.
These eggs hatch into larvae, which then burrow into the flesh of the host.
What are the symptoms?
As mentioned earlier, infections from NWS are intensely painful.
According to the CDC, signs of an infection include unhealing skin lesions, bleeding from painful sites, the sensation of larvae moving under the skin, or even in the nose, mouth, or eyes.
Infected individuals might also notice maggots around open wounds or on the body.
