Texas Horse Diagnosed With Screwworm Parasite, First Case This Century

The New World Screwworm makes history in Texas.

Texas Imposes Equine Movement Restrictions Following Screwworm Detection

A historic parasite case in West Texas has triggered new travel restrictions for livestock across multiple parts of the state. Federal and state equine authorities confirmed this week that a working ranch horse in Presidio County was diagnosed with a New World screwworm infestation on its hind leg, marking the nation’s first confirmed case in a horse during the 21st century. The quarantine order covers portions of both Presidio and Jeff Davis counties.

Vigilance is Key

Because screwworm larvae target healthy, living tissue rather than dead flesh, livestock managers should exercise extreme caution. Owners are advised to cleanse, shield, and inspect even minor cuts or scrapes daily until they fully heal.

Understanding the Travel Restrictions

The presence of the parasite has expanded the state's broader containment strategy. According to TAHC records updated Friday, the parasite has been identified across 39 locations spread throughout 17 Texas counties. To control the spread, state officials have designated specific containment zones within 16 counties:

Bandera, Brewster, Crockett, and Edwards

Jeff Davis, Jim Hogg, Medina, and Pecos

Presidio, Schleicher, Starr, and Sutton

Terrell, Uvalde, Val Verde, and Zapata

Designated Zone Restrictions

These localized quarantines apply strictly to designated zones rather than entire counties. Under the mandate, no warm-blooded animal within a restricted zone may be transported beyond its boundaries without formal clearance from state regulators. These transit barriers apply universally, whether an animal is heading to a local ranch, an auction, a rodeo, or an equestrian event.

Steps To Obtain Travel Permission

To obtain clearance for non-slaughter travel out of a restricted area, owners must adhere to a multi-step timeline:

Schedule an Inspection: Contact a certified or regional TAHC inspector at least 48 hours prior to the planned departure.

Clinical Exam & Treatment: An authorized inspector must physically evaluate the animal within five days of travel, verify its official identification, and ensure it receives an approved systemic parasite treatment.

Documentation: The inspector will issue a formal movement permit once requirements are met. Interstate transit still mandates a standard Certificate of Veterinary Inspection.

Infected Animals Cannot Travel Outside Quarantine Areas

Animals displaying active, unhealed wounds or live larval infestations are strictly prohibited from leaving quarantine areas until they undergo proper medical treatment and achieve complete healing. Because containment boundaries shift as new orders are enacted or lifted, owners should verify specific addresses on the TAHC interactive map before planning any transport.

Symptoms

The New World screwworm threat stems from female flies depositing eggs into open skin breaks or natural body orifices. After hatching, the larvae burrow deep into healthy muscle tissue, causing expanding lesions, severe secondary bacterial infections, and potentially fatal complications if left unaddressed.

Resurgence of the Screwworm

While the USDA eradicated the parasite nationally in 1966 and successfully contained an isolated outbreak in the Florida Keys in 2017, the current regional resurgence began earlier this summer when a calf in Zavala County tested positive on June 3.

Screwworm Symptoms

Without medical intervention, a screwworm infestation can kill an animal in as little as seven days. Livestock owners should routinely evaluate their herds for the following signs:

Unexplained swelling, fluid drainage, or foul odors around wounds

Signs of localized discomfort, biting, or scratching

Visible maggots, particularly near the eyes, nose, ears, mouth, genitals, or navels of newborns

Contact Information

Any suspected infestation must be reported to health authorities within 24 hours. Owners can report potential cases by contacting their local veterinarian, reaching out to a regional TAHC office, or calling the TAHC emergency veterinary hotline directly at 1-800-550-8242.