The new world screwworm is an aggressive parasite that poses a major threat to livestock health and the agricultural economy. Its recent spread in parts of Latin America and Mexico has caused alarm among U.S. officials and ranchers, leading to swift government action and increased biosecurity measures.
The new world screwworm (Cochliomyia hominivorax) is the larva of a particular type of fly. These larvae burrow into open wounds of warm-blooded animals, feeding on the host’s flesh. In severe cases, an infestation can kill even large animals like adult cattle within just a week or two. This pest was once eradicated in the United States thanks to coordinated sterilization and monitoring campaigns, but its northward advance from Central America has reignited concerns.
Recent outbreaks of the new world screwworm in Mexico have prompted agricultural authorities to act decisively. According to a USA Today report, the U.S. has indefinitely suspended live animal imports from Mexico. The parasites’ rapid reproduction and ability to devastate livestock herds make containment crucial. Past outbreaks have led to losses in the millions, and experts warn that a similar event now could cost the economy over a billion dollars.
To prevent the parasite from entering the US, the government halted the import of live cattle, horses, and bison. As described in detail by NPR, this move is not political but rather a necessary safety measure for animal and food security. Eradication efforts in the past used sterile insect release to break the reproductive cycle and create a barrier zone, a method still relevant today. Officials continue to monitor any new cases, especially on remote farms near the U.S.-Mexico border, and will adjust restrictions as the situation evolves.
The return of the new world screwworm underscores the importance of robust monitoring, strict import controls, and international cooperation. Agricultural agencies work closely with their counterparts in affected countries to manage and eventually eliminate this flesh-eating parasite. While the current ban on imports remains, efforts to contain and eradicate the screwworm are ongoing.
For more information on current regulations and updates on the fight against this threat, read NPR’s analysis on the halt of cattle imports and USA Today's coverage of screwworm outbreaks.
The new world screwworm remains a serious danger to livestock and agricultural stability. Ongoing vigilance, cooperation, and science-based interventions are vital for keeping this invasive parasite in check. Staying informed and adhering to safety guidelines will help protect animals and safeguard the food supply.