The United States Department of Agriculture (USDA) this week confirmed the first case of New World botfly infestation in Texas in almost six decades, reigniting concerns about the country’s livestock production and triggering a strong reaction in markets.
After confirming the presence of the parasite in a three-week-old calf in the south of the state, futures contracts for fattening cattle traded on the Chicago Stock Exchange (CME) rose more than 3%. Investors began to price in the risk of an even smaller supply of cattle in a market that is already facing a historic shortage of animals for slaughter.
The discovery comes at a delicate time for American livestock farming. The United States cattle herd is at its lowest level in 75 years, the result of prolonged droughts and rising feed costs that have led producers to reduce their herds in recent years.
What is the screwworm fly
The pest identified in Texas is caused by the larvae of the species Cochliomyia hominivorax, known as the screwworm fly or New World botfly.
Unlike other parasites, their larvae do not feed on dead tissue. They attack living tissues of warm-blooded animals, penetrating open wounds and causing injuries that can evolve into serious infections, organ damage and even death of the host.
The USDA said the infestation was detected in La Pryor in South Texas. The case is the first recorded in the state since 1966.
Continues after advertising
Although the parasite does not pose a risk to food security, experts warn that it can cause significant economic losses by reducing livestock productivity.
Market reacts to the risk of shortages
Confirmation of the case had an immediate impact on cattle prices.
Initially, futures contracts fell amid fears that consumers would reduce demand for beef. Throughout the trading session, however, the perception prevailed that an eventual spread of the plague could further restrict the supply of animals.
The result was a sharp rise in prices. Analysts estimate that a widespread infestation could generate losses of up to $1.8 billion for the Texas livestock industry alone.
The impact also worries large food processors, such as JBS, Cargill and Tyson Foods, which depend on a constant flow of animals to supply their operations.
Containment plan
The USDA mobilized emergency teams to try to stop the spread of the pest. The measures include the creation of a 20-kilometer control zone around the identified outbreak, restrictions on the movement of animals, quarantines and reinforced health surveillance.
Continues after advertising
The government also expanded the release of sterile flies, a technique historically used to control the species.
The method consists of creating millions of insects in the laboratory and sterilizing them using radiation. When these males reproduce with wild females, no offspring are produced, gradually reducing the parasite population.
According to US Secretary of Agriculture Brooke Rollins, the strategy was responsible for eradicating the pest in the country decades ago.
Continues after advertising
How the parasite returned
The screwworm fly had been eliminated from the United States after a long health campaign carried out over the last century.
In recent years, however, authorities have recorded an increase in cases in South America and Central America. Experts believe that the advance of the plague towards the north occurred after failures in the health barrier maintained between Panama and Colombia.
The USDA states that it has been monitoring the expansion of the parasite for months and had already suspended, in 2025, the entry of live animals through the southern border.
Continues after advertising
The agency also positioned sniffer dogs at checkpoints and sent teams to Mexico and Panama to reinforce control programs.
Cases in humans are rare
Although the main concern is the economic impact on livestock, the infestation can also affect humans.
Transmission occurs when flies lay eggs in open wounds. The larvae then begin to feed on the host’s tissue.
Continues after advertising
According to American authorities, human cases are uncommon. The most recent record in the United States occurred in 2025, in Maryland, involving a person who had traveled abroad and recovered after treatment.
The most vulnerable group includes farm workers, veterinarians, people who spend long periods outdoors, and individuals with exposed wounds.
Billionaire risk
The authorities’ fear is to avoid a repeat of episodes recorded in the past.
The largest outbreak in American history occurred in 1972, when around 90,000 cases were recorded. Estimates from the Dallas Federal Reserve indicate that a similar infestation could currently generate losses of more than US$3 billion in the southwest region of the country alone.
To avoid this scenario, the American government announced investments of US$750 million in a new facility in Texas designed to produce hundreds of millions of sterile flies per week.
The unit is expected to come into operation next year and will be one of the main bets to prevent the plague from establishing itself again in the United States.
