The United States has decided to stop importing livestock from Mexico in order to safeguard U.S. livestock from a dangerous parasite known as the New World Screwworm. The New World Screwworm, also referred to as the NWS, is a parasitic fly that was eliminated from the U.S. in the 1960s. This fly is notorious for its larvae feeding on animals by burrowing into open wounds, causing extensive damage by tearing at the host’s tissue with sharp mouth hooks, according to the Animal and Plant Health Inspection Service.
The suspension of imports was declared by U.S. Department of Agriculture Secretary Brooke Rollins on May 11, following the discovery of these flies in isolated farms approximately 700 miles south of the Mexico-U.S. border. The suspension will be reassessed on a monthly basis, as stated in a USDA announcement.
Here is what you need to know about the New World Screwworm and its past presence in the U.S.
New World Screwworm: U.S. Halts Livestock Imports from Mexico to Stop Parasitic Threat
What is the New World Screwworm?
The New World Screwworm is a parasitic fly similar in size to a common housefly. It features orange eyes, a metallic blue or green body, and three dark stripes along its back, as described by the Animal and Plant Health Inspection Service. This species of parasitic fly is known for its larvae feeding on living tissue.
The fly earns its name from the behavior of its maggots, which burrow or “screw” into open wounds of animals to feed. The New World Screwworm possesses sharp mouth hooks that enable it to penetrate deeply into an animal’s flesh. These critters can infest livestock, pets, wildlife, birds, and in rare instances, humans.
How does a New World Screwworm infestation start?
New World Screwworms primarily inhabit forests and wooded areas but may also target animals in pastures and fields if accessible. Flies are drawn to open wounds, even those as small as a tick bite, according to the USDA.
The infestation begins when a female lays eggs near an open wound on a warm-blooded animal. Within hours, the eggs hatch into larvae that burrow into the wound, consuming living flesh. After about a week of feeding, the larvae drop to the ground, burrow into the soil, and transform into adult screwworms. Flies emerge from the soil seven to 54 days later, restarting the cycle. During its lifespan, a female New World Screwworm can deposit up to 3,000 eggs, as per the USDA.
Infected animals typically display the following signs:
– Irritated behavior
– Head shaking
– Odor of decay
– Evidence of a fly strike
– Presence of fly maggots in wounds
Is the New World Screwworm a threat to humans?
While New World Screwworms can infest humans, such
Symptoms of New World Screwworm infestation may include feeling movement of larvae in a wound, as well as the presence of maggots in or around open sores located on the skin, nose, mouth, or eyes. An unpleasant odor from the affected area is common, and there is a risk of developing secondary bacterial infections which may lead to fever or chills.
The New World Screwworm infestation in the United States first became a major issue in 1933 following the transport of infested animals from the Southwest, as reported by the USDA. In response, the federal government introduced the Sterile Insect Technique in the 1950s. This method involved sterilizing male flies using radiation and releasing them into targeted regions to mate with females, resulting in the production of unfertilized eggs. By the early 1960s, Southern producers had suffered significant financial losses amounting to $50-100 million due to these infestations.
Thankfully, the implementation of the Sterile Insect Technique proved successful, leading to the official eradication of New World Screwworms in the US by 1966, according to the USDA. The total cost incurred by the federal government for this endeavor was $32 million. For media inquiries or story suggestions, please contact Greta Cross, a trending reporter at USA TODAY, via email at gcross@usatoday.com.
This content was originally published on USA TODAY: “New World Screwworm: What is the flesh-eating parasite?”
