A second alarming case involving a flesh-eating parasite has been identified in the United States.
The New World Screwworm (NWS) parasite, making its first appearance in the U.S. since 1966, has now been confirmed in Texas.
The initial case emerged on Thursday, with the U.S. Department of Agriculture confirming another outbreak the following day.
“The USDA has confirmed a second detection of New World Screwworm in a one-month-old calf in Zavala County, Texas—about 5.6 miles from the initial case,” the NWS Rapid Response team announced on X.
“In collaboration with our Texas partners, we are acting swiftly and decisively,” they added.
NWS flies are notorious for laying hundreds of eggs in open wounds on animals and humans. These eggs hatch quickly, and the larvae proceed to consume the host’s tissue.
The risk to humans is low, but these larval infestations can cause deep, painful wound infections. If left untreated, the infections can be deadly.
The rapid response team also shared that an Animal and Plant Health Inspection Service team is on-site of the second breakout.
Commonly called a New World Screwworm (NWS), the parasite has been confirmed in Texas after advancing across Mexico for the past year. Pictured are Texas cattle ranchers attending a presentation about the threat of the NWS
‘We have deployed mobile response trailers, and sterile fly releases are underway (two million aerial and four million ground per week).
‘Movement control zones are in place, surveillance is intensified, and treatment supplies are available through the Texas Animal Health Commission,’ they wrote.
The first case of NWS was also in a three-week-old calf in LaPryor, about 50 miles from the Mexico border. The parasite has advanced across Mexico for the past year.
A 12-mile quarantine zone was established for the first case, prohibiting the movement of any warm-blooded animal, including pets, outside that zone without an inspection.
Officials say the fly’s larvae threaten livestock, but they do not contaminate food.
Texas Governor Greg Abbott issued a disaster declaration in February as screwworms threaten the state’s booming beef industry, giving the state greater authority, resources and speed needed to confront the growing threat posed by the parasite.
When screwworms became a major problem in the US decades ago, it cost the US $200 million – roughly $1.8 billion today – in livestock.
The first case announcement came only a day after Rollins held an online news conference to highlight the proximity of the threat, with cases confirmed in Mexico as close as 25 miles from the border, and to outline the USDA efforts to combat it.
The months of effort to keep the parasite out of the US have included dropping millions of sterile screwworm flies in the area to mate with wild females.
This is the same method used successfully before the NWS was eradicated.
NWS can also infest people and pets, but the risk to humans is low. However, these infestations can lead to deep, painful wounds that become infected and often result in death if left untreated
A test container of dyed fly pupae are displayed at a Domestic New World Screwworm Sterile Fly Production Facility to combat the northward spread of NWS and protect American livestock
Rollins said the USDA is confident enough in its preparations that it believes ‘there is no threat of mass infestation.’
‘There is no reason to believe this incursion will result in the establishment of the pest in our country,’ Rollins said.
New World screwworm is not contagious and does not spread directly between animals or people, according to the Animal and Plant Health Inspection Service.
The screwworm begins its attack when a female fly lays her eggs in an open wound or body orifice.
These flies are attracted to the scent of exposed tissue and openings, which can be as small as a tick bite, a nasal or eye passage, a newborn’s navel, or genital areas, according to the Texas Parks and Wildlife Department (TPWD).
Once laid, the eggs hatch into larvae that burrow into the flesh like tiny screws, the agency said.
A single female can lay 200 to 300 eggs at a time and as many as 3,000 over her lifetime. Infestations may also become visible on the skin.
