Health authorities in Texas are racing to contain a dangerous parasite outbreak after a working ranch horse in Presidio County was infected with the New World screwworm. This marks the first US equine infection during the current outbreak. The screwworm is a fly larva that nestles into and infests open wounds, and it can cause severe injury or death in animals.
The parasite was eradicated in the United States decades ago, but it has re-emerged as an infestation spreads through Mexico. It was detected in June on a calf in Zavala County near the US-Mexico border. Out of 49 US cases recorded this year, 48 have been in Texas and one was found on a dog in New Mexico.
The resurgence of the parasite has raised serious alarms about potential financial devastation for Texas ranchers. In response, Texas Governor Greg Abbott issued a disaster proclamation in June to mobilize state resources. To curb further infestations, the Texas Animal Health Commission has restricted the movement of warm-blooded animals out of infested zones in parts of Presidio and Jeff Davis counties.
To manage the outbreak, horse owners are advised to inspect their animals daily for wounds, foul odors, or maggots, and to use fly control products. Authorities are also using a sterile fly dispersal facility in Edinburg. When female screwworm flies mate with sterile flies, they produce no viable offspring, helping to reduce the parasite population.