New World screwworm crosses state lines, prompting border restrictions and renewed slaughter-pipeline fight

A new New World screwworm detection in Texas is pushing U.S., Canadian and Mexican authorities to tighten animal transport rules as states weigh how to protect livestock, pets and people. Horse Plus Legislative Coalition says the outbreak underscores broader risks tied to horse transport, animal trafficking and gaps in enforcement.

Why it matters: - New World screwworm is a flesh-eating parasite that can severely damage livestock, pets, wildlife and, less often, birds and humans. - The Texas cases have already triggered cross-border animal restrictions, raising the stakes for livestock movement across state and international borders. - Horse Plus Legislative Coalition says ending horse transport for slaughter would help reduce disease spread and other criminal activity tied to the pipeline.

What happened: - The U.S. Department of Agriculture’s Animal and Plant Health Inspection Service confirmed New World screwworm in a 3-week-old calf in Zavala County, Texas, in a June 3, 2026 report. - A second case was confirmed less than 6 miles away. - At the time of the release, another calf and a goat had been diagnosed in Texas in different counties, and a dog had been diagnosed in New Mexico. - Horse Plus Humane Society said it conducted a 2-year undercover investigation that led to warnings about zoonotic diseases and the presence of New World screwworm in the U.S. - Horse Plus Legislative Coalition said it has alerted 140 leaders in border and agricultural states about the parasite.

The details: - New World screwworm, Cochliomyia hominivorax, was eradicated in the United States in the 1960s but remains present in Mexico and endemic in South America and Caribbean countries. - Female screwworm flies mate once and lay 200 to 300 eggs in open wounds or around body orifices. - The eggs hatch in 5 to 7 days, and the larvae feed aggressively on flesh and expand wounds. - Full-grown larvae drop off the animal, burrow into soil, form pupal casings and mature into adult flies. - The full life cycle can take 7 to 54 days. - The Canadian Food Inspection Agency has closed the border to animals that have been in Texas within the prior 21 days to reduce spread risk. - CFIA says U.S. states are taking similar measures. - NWS in Texas also triggered border closings that block horse transport into Mexico and Canada. - HPLC said evidence it presented should prompt authorities to keep borders closed beyond the period when the infestation is controlled. - The coalition said horse transport to slaughter can mask crimes including drug smuggling, zoonotic diseases, human trafficking, horse theft, illegal horse butchering and meat sales, extortion and money laundering. - The release described multiple drug-smuggling methods tied to horse transport, including hiding drugs in trailers, placing packets in mares, inserting packets through nasal-gastric tubes and creating pockets under horses’ skin. - The release said rejected horses are sometimes used to move drugs when shipments are turned away in Mexico. - HPLC said the slaughter pipeline can spread zoonotic disease because humans and horses are packed closely in transport vehicles. - The release said diphtheria has been diagnosed in horses rescued from the slaughter pipeline after extended exposure to infected humans. - HPLC said informants exposed human-trafficking and sex-trafficking activity linked to the pipeline. - The coalition said horse theft can be hidden through false paper trails. - HPLC said DNA testing showed horse meat has been sold to restaurants and food trucks in Texas and Florida. - The release said informants reported refrigerator trailers at auctions being used as illegal butchering sites. - The coalition said unregulated meat is dangerous because drugs used in horses can be toxic to humans. - The release said extortion can take the form of threats that horses will be shipped to slaughter. - HPLC said money laundering is enabled by cash-heavy auctions and high fees for other payment methods. - The release said veterinary health certificates and a negative Coggins test for Equine Infectious Anemia are required for interstate travel, but a loophole allows truckloads of horses designated for slaughter to move through Texas with a permit number and no health documentation. - Horse Plus Legislative Coalition and other organizations have met with congressional offices about the SAFE Act Amendment in the Build America Act 250 / HR8870. - The SAFE Act Amendment has 229 bipartisan House cosponsors. - The release said more than 80% of Americans oppose transporting horses for slaughter in an ASPCA survey. - The release said a more recent survey by Advocates for Wild Equine National Grassroots Coalition found more than 90% oppose that transport.

Between the lines: - The release ties a public health and animal-health outbreak to a broader campaign against horse slaughter transport. - HPLC is using the screwworm detection to argue that state-by-state border controls are not enough if horses continue moving through the slaughter pipeline. - The group frames the issue as both a disease-control problem and a criminal-enforcement problem. - The release also suggests the outbreak could strengthen political momentum for the SAFE Act Amendment because it already has broad bipartisan support in the House.

What’s next: - HPLC said horse buyers who move animals for slaughter are already looking for ways around Canada’s precautions. - Britta Hesla said the coalition will keep pressing state and federal lawmakers to pass HR8870 with the SAFE Act included. - The release calls on horse owners to care for their animals responsibly and ethically. - More state and federal border or transport restrictions could follow if additional screwworm cases are confirmed.