November 22 The U.S. Department of Agriculture has temporarily suspended cattle imports from Mexico after a carnivorous parasite was detected in the animals in southern Mexico. Before the discovery of the cattle snail (Cochliomyia hominivorax) at a checkpoint in the state of Chiapas, this species had already been eliminated in North America since the behind schedule 19th century. The U.S.-Mexico border remains closed to cattle and may not reopen until the fresh year.
The worm is the larva of a metallic blue-green fly that spends the early part of its life cycle consuming live mammalian meat. Infections can be fatal. Cows are the snail’s favorite treat, but worms it can also feed on other farm animals as well as wildlife and pets. Flies often lay eggs near open wounds, and if the larvae find a hole in the skin to release their acute hooks, they burrow into the animal’s body and devour.
The discovery in Mexico follows the recent re-emergence of the parasite in Costa Rica, Nicaragua, Honduras and Guatemala. Faced with the re-emergence of the parasite, Mexico is stepping up sanitation measures – calling for the treatment of livestock wounds, larvicidal baths and deworming of cattle – and has introduced inspection stations like the one that detected the case in Chiapas. But conservationists from the Wildlife Conservation Society and Mexican farmers warn that the illegal cattle trade will be the real gateway for the disease to enter North America.
Before the U.S. border closed, the National Confederation of Cattlemen’s Organizations of Mexico called on the government to end cattle smuggling across Mexico’s southern border. The risk from the parasite is great, and if it re-establishes itself, the cost of eradicating it in Mexico will be high. Disrupting trade with the US was also very costly. In 2023 alone, live cattle and beef exports from Mexico to the United States were worth $3 billion.
On the trail of the Screwdriver
For almost two decades Cochliomyia hominivorax was eliminated from the United States as far as the Darien Gap in Panama. That was until the summer of 2023, when Panama detected a acute boost in animal invasions within 300 kilometers of the northern border with Costa Rica, marking the beginning of the parasite’s re-emergence in Central America.
Costa Rica, declared free of the aggressive parasite in 1999, subsequently documented outbreaks in July 2023. Nicaragua and Honduras, free of the snail since 1996, confirmed cases in April and September of this year, respectively. Then 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 obvious. According to the Panama-United States Commission for the Control and Prevention of Slugworms, as of November 2, 2024, there have been 15,638 cases of slugworms reported in these four countries, including 20,890 cases documented in Panama.
In reports submitted to the World Organization for Animal Health, three of these countries – Costa Rica, Nicaragua and Honduras – indicated illegal animal transit as the source of infection on their territory. Honduras detected the outbreak after examining 68 horses that had entered the country illegally, for example just 8 kilometers from the border with Nicaragua.