November 22nd, The U.S. Department of Agriculture has suspended imports of cattle from Mexico after a meat-eating parasite was detected in animals in southern Mexico. Before the screwworm was discovered (Cocliomia hominivorax) According to testing points in Chiapas, this species has been eliminated from North America since the end of the 19th century. The U.S.-Mexico border remains closed to cattle and may not reopen until the new year.
The insect is a metallic blue-green fly larva that spends the early part of its life cycle devouring the living flesh of mammals. Parasitism can be fatal. Screw maggots’ favorite food is cows, but maggots can also eat other domestic animals, wild animals, and pets. The flies often lay their eggs near open wounds, and if the larvae can find a hole in the skin to deploy their sharp hooks, they will bury themselves in the animal’s flesh or canyons.
The discovery in Mexico follows recent re-emergence of the parasite in Costa Rica, Nicaragua, Honduras and Guatemala. In the face of a resurgence of this parasite, Mexico has stepped up hygiene measures, requiring the treatment of livestock wounds, larvicidal baths, and deworming of cattle, such as the one detected in Chiapas. An inspection laboratory has been introduced. But conservationists with the Wildlife Conservation Society and Mexican ranchers warn that the illegal trade in cattle is the real gateway for the disease to enter North America.
Before the U.S. border closed, Mexico’s national federation of livestock groups called on the government to crack down on cattle smuggling across Mexico’s southern border. The risks posed by this parasite are significant, and if it were to reestablish itself, the cost of eradicating it in Mexico would be high. Interruption of trade with the United States was also costly. Live cattle and beef exports from Mexico to the United States reached the equivalent of $3 billion in 2023 alone.
Screw maggot footprints
For about 20 years, Cocliomia hominivorax They were excluded from the United States to the Darien Gap in Panama. It lasted until the summer of 2023. In Panama, a spike in animal infestations was detected within 300 kilometers of the northern border with Costa Rica, and the parasite has begun to re-emerge in Central America.
Costa Rica declared itself free of this aggressive parasite in 1999, then recorded an outbreak in July 2023. Nicaragua and Honduras have been free of the screwworm since 1996, but confirmed cases in April and September, respectively. And in October 2024, Guatemala reported the re-emergence of the fly and its larvae, with the first fatality being a calf. The threat to countries further north is clear. As of Nov. 2, these four countries have accumulated 15,638 screwworm cases in 2024, with Panama recording 20,890 cases, according to the Panama-U.S. Screwmaggot Eradication and Prevention Committee.
In reports submitted to the World Animal Health Organization, three of the countries, Costa Rica, Nicaragua and Honduras, cited illegal transport of animals as a source of infection within their territories. Honduras, for example, discovered the outbreak after testing 68 horses that entered the country illegally just 8 kilometers from the border with Nicaragua.
(Tag translation) Science
