United States – A dangerous parasite known as the New World screwworm has re-emerged in parts of the United States, raising concerns among veterinarians, livestock owners, and pet parents alike.
Unlike typical maggots that feed on dead tissue, screwworm larvae feed on the living flesh of warm-blooded animals, including livestock, wildlife, pets, and, in rare cases, humans. The larvae are the offspring of the New World screwworm fly (*Cochliomyia hominivorax*).
Historically, the screwworm was a major problem throughout the southern United States until an aggressive eradication program using sterile flies eliminated the pest from the U.S. by the 1960s. However, the parasite remained present in parts of South America, the Caribbean, and Central America.
According to the U.S. Department of Agriculture (USDA), a recent outbreak that has moved north through Central America and Mexico has now resulted in **confirmed cases in Texas and New Mexico**, marking the first locally acquired U.S. cases in decades. Officials believe the parasite spread northward through the movement of infested animals and wildlife.
Why is the screwworm so dangerous?
Female screwworm flies lay their eggs in open wounds, surgical sites, tick bites, the navels of newborn animals, and even natural body openings. Once the eggs hatch, the larvae burrow deeper into living tissue, causing severe pain, tissue destruction, secondary infections, and, if left untreated, death.
Signs of a possible screwworm infestation include:
* Wounds that rapidly worsen or enlarge
* Bloody or foul-smelling discharge
* Visible maggots in a wound
* Excessive licking or biting at an injury
* Irritability or signs of pain
* Loss of appetite
* Head shaking (particularly if the ears are involved)
* Fever or lethargy related to secondary infection
How can pet owners help prevent infestation?
* Promptly clean and monitor all wounds.
* Keep surgical incisions protected and check them daily.
* Use veterinarian-recommended parasite prevention products.
* Seek veterinary care for wounds that fail to heal or appear infected.
* Avoid delaying treatment if maggots are observed in any wound.
Can screwworm infestations be treated?
Yes—but immediate veterinary care is critical. Treatment generally involves removing the larvae, thoroughly cleaning the wound, administering medications to kill remaining larvae, and treating any secondary infections. The sooner treatment begins, the better the outcome.
While the average pet owner is unlikely to encounter a screwworm infestation, awareness is essential. Early detection can save lives and help prevent the spread of this devastating parasite.
If you suspect a screwworm infestation in your pet or livestock, contact your veterinarian immediately and follow local reporting guidelines.
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