A rare case of New World screwworm, a parasite that consumes living tissue and can be fatal to humans, has been identified in a U.S. resident.
The U.S. Department of Health and Human Services (HHS) informed TIME via email that a person residing in Maryland contracted a screwworm infestation after traveling to El Salvador, a story first reported by Reuters. Central America is currently battling outbreaks of this damaging pest, which poses a threat to both livestock and humans. The U.S. embassy in Nicaragua reported in July that cases had been recorded in the past year.
The U.S. Centers for Disease Control and Prevention (CDC) verified the Maryland case on August 4 after examining images of the insect responsible for the infestation, according to HHS.
The agency stated, “This is the first instance in the United States of a human contracting New World screwworm [infestation] linked to travel from a country affected by an outbreak. At present, the risk to the American public from this occurrence is minimal.”
Reports indicate that the U.S. cattle and livestock industry is concerned about the human case. Screwworm has the potential to spread rapidly and can kill adult cattle in a little over a week, . The U.S. Department of Agriculture stated earlier this month that the pest closely linked to the cattle and livestock industry.
The New World screwworm is a fly species that deposits its eggs in open wounds or on the mucous membranes of mammals and birds, such as in the nasal passages. When these eggs hatch, maggots emerge and on living tissue, as stated by the CDC. The name “screwworm” comes from the way these maggots use their sharp mouth hooks to burrow into flesh.
The CDC notes that screwworms can lead to significant tissue damage and secondary bacterial infections. Infestations are extremely painful and can be deadly if not treated without delay. There is no approved medical treatment for screwworm infestations in humans. A medical professional must manually remove the maggots, which can number in the hundreds.
Although details about the Maryland resident who contracted the screwworm infestation have been limited, state health officials have confirmed the individual has recovered, . A spokesperson for the Maryland Department of Health informed the outlet that there was no evidence that the person’s infestation had spread to other people or animals.
The news of the Maryland case follows the U.S. government’s recent announcement of measures to prevent screwworm outbreaks and safeguard the U.S. cattle and livestock industry from the pest. These measures include authorizing the to treat or prevent infestations in animals and constructing a sterile fly facility in Texas. The New World screwworm was eradicated from the U.S. in the 1960s by releasing large numbers of sterilized male screwworm flies, which then mated with wild female screwworms, resulting in infertile eggs.
The same method was used to manage a small screwworm outbreak in Florida in 2017.
Although screwworm infections in humans are uncommon in the U.S., there have been a few cases in recent years involving travelers returning to the country from regions where the pest is common. In 2023, a traveler returning to Arkansas after visiting Argentina and Brazil developed a screwworm infestation in a surgical wound, . In the previous year, a traveler returned to Florida with an infestation acquired during a vacation in the Dominican Republic.
