First human case of screwworm adds to concerns over livestock and beef costs
Mitchell Kaminski
COLUMBIA, Mo. (KMIZ)
The first reported case of a flesh-eating parasite in a human was confirmed by the U.S Department of Health and Human Services on Monday.
The Maryland resident who was diagnosed has recovered from the infection. According to HHS, a person who traveled to El Salvador was diagnosed with New World screwworm, a species of parasitic flies that feed on live tissue. The fly gets its name from the way that maggots screw themselves into animal tissue with their sharp hooks.
“The screwworm is a blue-green blowfly. It’s a bit bigger than a housefly,” Max Scott, a professor of Entomology and Plant Pathology at North Carolina State, told the Associated Press through ABC News. “It gets its common name, a screwworm, named after the maggot stage because it’s found in the sort of infested animals, and the screwworm looks like it’s sort of screwing itself into the flesh as they’re eating the animal.”
The Missouri Department of Health and Senior Services told ABC 17 News that it has been in contact with the CDC, but that the health risk to the general public is “very low”. While there have not been any human cases reported in Missouri, the New World screwworm could have an impact on beef prices, which have already hit record highs.
Countries across Central America and Mexico are grappling with a surge of livestock infections caused by the parasitic screwworm, which tends to be more prevalent in poor rural areas in South America.
After a case of New World screwworm was confirmed about 370 miles south of the U.S.–Mexico border in July, U.S. Secretary of Agriculture Brooke Rollins ordered the closure of southern ports of entry to livestock trade. The northward detection came just two months after cases were reported less than 700 miles from the U.S. border, which had already prompted the shutdown of ports to Mexican cattle, bison, and horses in May.
“[Mexico] supplies maybe about 5% of the animals that are used here for the domestic beef production. So that’s a shock that maybe a lot of people in the market already see and they think about.” Wyatt Thompson, a University of Missouri Professor of Agriculture and Applied Economics, said. “The questions are when those bans on live imports might stop, if at all and those live cattle keep coming across the border again, and maybe alleviate some of the supply pressures, given that we have low coverage right now.”
Wesley Tucker, a livestock economist and field specialist at the University of Missouri, says ranchers protect their livestock from parasites with increased management and vigilance. Typically, that means inspecting animals for open wounds that could attract pests. If problems are found, Tucker says producers must act quickly to prevent the spread of infection.
“If screw worms were to migrate into the U.S., it would impact how ranchers perform normal animal husbandry practices, such as when to calve, when to give vaccinations or castrate animals. Each of these practices creates an open mound which could be a source of infection by the fly,” Tucker explained.
“Therefore, an outbreak here in the U.S. could have impacts on how producers raise cattle and would greatly increase the labor required. Producers must increase their efforts for fly control to protect their animals. With the age of the average rancher increasing it this could have impacts upon our industry and beef produced in the coming years.”
Missouri farmers are already feeling the squeeze due to drought, inflation, and shrinking cattle herds. This, mixed with a high demand for beef, has fueled high prices. Thompson says that the outbreak in Mexico could reduce U.S exports, which also affects prices.
“The absence of live cattle imports certainly does have upward price pressure, and I think it might be built into the prices we see now, because that’s already happening to an extent,” Thompson explained. “[If] the border is reopened and imports resumed, then you’d imagine some of the price pressure would be alleviated and maybe the price wouldn’t go as high as they might otherwise. But a lot of the story of the high prices is other things going on as well.”
In Panama, livestock infections jumped from just 25 cases a year to more than 6,500 in 2023, according to the U.S. Department of Agriculture. The parasite has now spread into seven other Central American countries, breaking through a barrier that had kept it locked in South America for decades.
The USDA says screwworm has not been found in U.S. livestock. The parasite was wiped out in the U.S in the 1960s, after scientists released sterilized male flies that mated with females but produced no offspring, eventually wiping out the population.
However, the USDA acknowledged in a press release that the spread in neighboring states is a “now only a threat to our ranching community, but is also a threat to our food supply and our national security.”
In an August 15th press release, the USDA outlined several new efforts. They include working with the Army Corps of Engineers to build a facility capable of producing up to 300 million sterile flies, which will operate alongside plants in Panama and Mexico. The plan also calls for mounted patrols and detector dogs to monitor wildlife crossings at the border, and up to $100 million in funding for new technology to speed up sterile fly production.
Earlier this month, the FDA also granted an Emergency Use Authorization for animal drugs to help treat or prevent screwworm infections.
