First US screwworm case in 60 years: Should America be worried?

The New World screwworm, a flesh‑eating parasite which infects cattle and different warm‑blooded animals, has been recovered successful a calf successful Texas, the US Department of Agriculture announced connected Wednesday.

The screwworm is believed to person travelled from Central America to Mexico earlier being recovered successful the calf successful Texas, evading biologic barriers that person kept the pest contained for decades, experts said. Screwworm was antecedently declared eradicated successful the US successful 1966.

Between mid-July and mid-August 2025, Mexico reported a 53 percent rise successful the fig of cases successful animals. Humans tin besides beryllium infected.

An outbreak successful the US could heavy interaction the livestock manufacture and origin accrued beef prices. The USDA predicts that could outgo the Texas system $1.8bn successful losses.

Here is wherefore the archetypal confirmed lawsuit successful six decades is truthful concerning.

What is screwworm and tin humans beryllium infected?

A screwworm comes from the larvae of a screwworm fly, besides called Cochliomyia hominivorax and, yes, humans tin beryllium infected.

Female screwworm flies laic their eggs successful scratches and wounds of warm-blooded animals, usually livestock oregon chaotic animals. The eggs hatch into hundreds of screwworm larvae which devour the surviving insubstantial of the infected animals.

The flies are attracted to the odor of unfastened wounds connected the bodies of these animals, oregon sometimes adjacent of humans. Newborn calves are astatine precocious hazard due to the fact that the post-partum navel has yet to scar.

The larvae usage their crisp mouths to burrow done the surviving soma of their hosts for astir a week.

Then they driblet to the ground, signifier a pupa and make successful the crushed for different week to 2 months earlier emerging arsenic an big fly.

Screwworm tin beryllium devastating successful cattle and wildlife which tin dice from corruption if untreated.

As big screwworm flies are susceptible of travelling galore kilometres successful hunt of hosts, infestations tin dispersed rapidly crossed wildlife populations, livestock herds and betwixt humans.

Dr Timothy Goldsmith, a veterinary medicine prof astatine the University of Minnesota, told Reuters that stateless radical tin beryllium particularly susceptible to infestation due to the fact that they slumber extracurricular and person little entree to hygiene products and aesculapian care.

It is uncommon for radical to drawback screwworm, however, and they cannot beryllium infected by New World screwworm from eating normal, inspected, cooked beef.

Last year, Mexico confirmed 41 quality cases, chiefly successful the authorities of Chiapas, according to Mexican media.

The New World screwworm is simply a taxon of parasitic alert that is known for the mode its larvae devour surviving insubstantial [Shutterstock]

What are the symptoms?

Screwworm infestations successful wildlife and humans origin painful, progressive wounds arsenic larvae burrow into surviving tissue. Symptoms see open, foul-smelling sores that enlarge rapidly, with disposable maggots inside.

Affected animals whitethorn amusement weakness, reduced mobility, value nonaccomplishment and abnormal behaviour from distress. In humans, symptoms see terrible pain, swelling, fever and secondary infections.

Screwworm is diagnosed chiefly by ocular recognition of larvae successful wounds. The maggots person distinctive features, specified arsenic acheronian tracheal tubes disposable done their bodies with bands of spines astir each segment.

If untreated, infestations tin pb to insubstantial demolition and adjacent death.

How is screwworm treated?

Painfully.

The hundreds of larvae which hatch successful a coiled person to beryllium manually removed, and the wounds indispensable beryllium disinfected.

Antibiotics are often prescribed to power secondary bacterial infections, and symptom absorption whitethorn beryllium indispensable successful terrible cases.

In animals, insecticides are utilized to termination remaining larvae and forestall re-infestation.

With thorough care, betterment is possible, but untreated cases tin pb to extended insubstantial harm and death.

How are authorities responding to this latest lawsuit successful Texas?

The existent lawsuit concerns a three-week aged calf infested with screw worm successful LaPryor Texas, astir around 50km (30 miles) from the Mexican border.

“This is regarded arsenic a locally acquired infestation with the larvae infesting the umbilical cord of the calf,” Cheryl Whitehorn, aesculapian entomologist and main technological serviceman astatine the London School of Hygiene and Tropical Medicine (LSHTM), told Al Jazeera.

A quarantine portion spanning 20km (12.4 miles) has been established astir the affected workplace with nary question of immoderate animals including pets, the carnal is being treated and the larvae volition beryllium killed, Whitehorn said.

“The superior measurement is vigilance, recognition and isolation of cases, attraction and elimination of larvae and controlling question of animals. A programme of sterile antheral merchandise is the champion semipermanent method of controlling this fly,” she said.

Why is this significant?

Last August, the US Department of Health and Human Services (HHS) reported America’s archetypal ever quality lawsuit of New World screwworm.

The case, investigated by the US Centers for Disease Control and Prevention (CDC) progressive a diligent who had returned from El Salvador to the US authorities of Maryland. Local quality reports suggested the diligent made a afloat recovery.

The caller lawsuit successful a Texas calf is important due to the fact that it is the archetypal clip New World screwworm has been detected successful animals successful the United States since it was declared eradicated successful 1966. That followed the monolithic merchandise of sterile flies which killed disconnected existing populations.

The parasite reappeared successful Panama, Costa Rica, Nicaragua, Honduras, Guatemala, Belize and El Salvador earlier moving connected to Mexico successful 2023.

While the precise reasons are unclear, experts constituent to a operation of factors, including imaginable disruptions to sterile‑fly programmes during the COVID‑19 pandemic, accrued question of livestock and people, and favourable upwind conditions that person helped the alert to thrive.

How does this interaction beef prices?

Washington has halted cattle imports from Mexico for the past year, citing the insect’s dispersed further into Mexico.

The US typically imports much than 1 cardinal Mexican cattle annually. The import suspension contributed to rising beef prices by tightening the proviso of beef cattle, which dwindled aft a drought forced ranchers connected some sides of the borderline to trim herds.

A US outbreak would origin further shortages to the cattle proviso and enactment different livestock and household pets astatine risk.

Mexican cattle are usually fed and fattened connected US farms for 5 to six months earlier slaughter, and a diminished slaughter complaint tin besides rise beef prices.

With US cattle herds already astatine a multi‑decade debased aft terrible drought, precocious provender costs person forced ranchers to shrink their herds. The suspension of US imports of unrecorded cattle from Mexico has pushed record‑high beef prices adjacent higher, arsenic much calves person been kept retired of the US proviso chain.

The archetypal confirmed lawsuit successful the US during the latest outbreak represents a superior situation for ranchers and could origin beef prices to emergence further.

After decades of eradication, astir cattle ranchers nary longer person the acquisition oregon tools to diagnose and dainty screwworm, experts say.

Infestations tin beryllium cured, but attraction is simply a time-consuming, pricey and labour-intensive process.