Experts warn of new challenges in controlling the new world screwworm spread across the US

Experts are raising concerns about the potential spread of the new world screwworm in the US, driven by illegal cattle movement and the parasite's endemic presence in Central America. As scientists continue to monitor wildlife, they are discovering alarming signs of infection that could complicate eradication efforts.

Current Spread of the Screwworm

Recent findings reveal that the screwworm has been detected in 34 animals within the US, primarily in Texas and one case in New Mexico. The parasite is mainly affecting livestock and pets, with no wildlife detections reported in the country so far. The Wildlife Conservation Society's director, Jeremy Radachowsky, noted that the cameras set up to monitor illegal cattle trafficking also captured various wildlife, including jaguars and deer, infected with screwworm.

Radachowsky stated, “We see infestations in the deepest parts of the interiors of the forest, so now it’s become endemic in wildlife, far from the cattle infestations.” This situation illustrates how the screwworm could spread further into the US.

Control Efforts and Challenges

In response to the outbreak, the US is deploying 100 million sterile flies across the southwestern region and into Mexico. Experts believe that while this may slow the parasite's northward movement, it won't be sufficient for complete eradication. Phillip Kaufman, a professor at Texas A&M University, emphasized the need for at least 500 million sterile flies to effectively push the population back south.

The breeding capacity for sterile flies is being expanded, with new facilities planned in Texas and Mexico. These flies are irradiated to prevent reproduction, allowing populations to crash when they mate with wild females. Kaufman stated, “We have to have things that work.”

Underlying Causes and Future Solutions

While current efforts focus on eradicating the screwworm, experts warn that addressing the root causes, such as illegal cattle trafficking, is crucial. Radachowsky pointed out that the livestock industry has changed significantly since the last eradication in 1966. He remarked, “There’s this expectation that the sterile fly technique worked once, so it will work again.” However, the current high density of cattle and illicit movements complicate matters.

The screwworm's resurgence has been linked to illegal trafficking routes, as it moved rapidly through Central America. Kaufman noted, “When you see it jump 50 or 100 miles, that wasn’t an adult fly flying that far. It was people.” Innovative solutions, such as focusing on raising only sterile male flies or improving bait traps, are being explored, but they require time for development and testing.