The U.S. Department of Agriculture confirmed New World Screwworm has expanded into Texas, according to a statement from the U.S. Equestrian Federation. It was found in a calf in Zavala County. Officials have been watching for months as the infestation moved toward the border from Mexico.
It spreads via maggots that feed on living tissue of any warm blooded animal, including people. Horses, cattle, wildlife pets and their owners could all be affected. Rapid detection and response are essential. The larvae are deposited on wounds or superficial body cavities, such as the nose and sheath of horses, where they feed and grow. Untreated wounds often develop multiple infestations which are more likely to kill the animal.
Widespread screwworm infestation could have serious consequences for animal health, agriculture productivity, and the national economy. A widespread outbreak will disrupt livestock movement and trade, increase veterinary and surveillance costs, and place major burdens on producers, animal health officials, and event organizers. Early detection and response is critical to stop the spread, according to USEF.
Horse owners can protect their horses from screwworm by checking daily for any wounds, drainage, foul odor, or unusual irritation, and by cleaning and protecting even minor cuts as soon as they are found to reduce the opportunities for the screwworm fly.
Consistent fly control, good stable hygiene, and careful monitoring after injuries or surgery can help reduce risk, since screwworm flies are attracted to open wounds and body openings. If a horse develops a wound that worsens quickly, has a bad smell, or contains visible maggots, the owner should contact a veterinarian immediately so the horse can be evaluated, treated and reported if needed.
Federal and state animal health officials will dictate the procedures around screwworm cases. USEF can help competition organizers and participants. Horses infected with screwworm or in a geographic area with screwworm present are likely to be placed under quarantine.
State animal health officials will have the discretion to implement movement restrictions in these situations. States may restrict equine movement and activities in a geographic area. State and federal animal health officials are finalizing the protocols for responding to screwworm incursion. Those who live in or are traveling to a state where screwworm has been reported should visit the website of the relevant state veterinarian for the latest information on screwworm response and prevention.
USEF veterinarians are working with the states to develop a response plan that would allow healthy, safe competition to continue in the event of a screwworm detection in the U.S. Any protocol for events during a screwworm incursion would be at the discretion of state veterinarian. Entry requirements for an event could include a requirement for veterinary examination for issuance of a certificate of veterinary inspection, which includes an antiparasitic treatment (ivermectin/dectomectin) statement and examination on arrival. The Federation will post updates and protocols on the dedicated New World Screwworm webpage at this link.