New World Screwworm | A Growing Concern for Texans

The recent news regarding the reemergence of the New World Screwworm poses a significant threat to Texans, pets, wildlife and all warm-blooded species. This invasive pest is known for infesting open wounds and can lead to severe health issues in affected animals.

Given its name, the New World Screwworm would seem to be a caterpillar; however, this parasite is really a fly that can travel miles, wreaking havoc on livestock and wildlife.

Recently, the cases detected of the New World Screwworm in the U.S. have originated in Mexico and Central America. Restrictions by the USDA on live animal imports from Mexico remain in place.

The New World Screwworm was originally eradicated in the U.S. in the 1960s. It occasionally reemerges in Central America and in Mexico. These historical resurfaces are controlled through a technique of releasing sterile males into the environment, known as the sterile insect technique.

As the situation develops, it is essential for all Texans to stay informed and take necessary precautions to protect their animals and property. Early detection is crucial in managing and mitigating the spread of the pest.

What it is: The New World Screwworm is a parasitic fly; it’s larvae can severely impact livestock

What it looks like: Metallic blue fly with three distinct stripes that run down its top just behind the head, with large orange eyes

Where did it come from: Native to the Western Hemisphere, Central America, Mexico

Reason for Concern: The fly lays eggs in the living tissue of fresh wounds of warm-blooded animals. The maggots burrow, “screw,” into the animal’s wound, causing the wound to become severe resulting in death if untreated.

Method of Action: Continual and regular monitoring and evaluation of livestock.

Identifying New World Screwworm in Livestock

Producers should stay vigilant to possible signs associated with parasite infestation including:

Foul smelling maggots
Animals biting and licking wounds
Lesions in navels, ears and dehorning or branding sites
Unusual restlessness or lethargy

Can we identify the larvae of the screwworm on our own?

No. Official identification of larvae is based largely on the presence or absence of internal breathing tubes determined by a trained specialist. If you come across a suspicious specimen, you can submit the specimen to the Texas Animal Health Commission.

What do I do if I suspect a case?

Immediately contact your local veterinarian and/or