The reappearance of the New World screwworm in Texas for the first time since 1966 highlights the growing limits of national sovereignty in an interconnected world. The flesh-eating parasite, which threatens livestock and the $113 billion US cattle industry, spread north from Central America and Mexico before being detected in Texas in 2026. Its return demonstrates that many contemporary challenges cannot be controlled by national borders alone. The New World screwworm is a flesh-eating parasitic fly whose larvae infest and consume the living tissue of livestock and other mammals.
Although some US politicians focused on border controls and animal movements, scientists have pointed to a deeper global factor: climate change. According to researchers, the screwworm historically struggled to survive in the southern USA because winter cold snaps acted as a natural barrier. As temperatures rise, these cold periods are becoming less frequent and less severe, removing a key ecological constraint on the parasite’s northward expansion. Climate change is therefore not simply an environmental issue; it is helping to reshape the geographical distribution of disease and agricultural pests.
This creates a direct challenge to policies associated with Donald Trump. The Trump administration has consistently opposed many forms of international climate cooperation and questioned the urgency of climate action. Yet the screwworm’s return demonstrates how climate-related changes occurring across an entire region can generate domestic consequences inside the USA. At the same time, cuts to a USAID-funded programme that monitored and contained screwworm populations in Central America reduced efforts to tackle the problem before it reached the US border. In effect, both climate change and the weakening of international monitoring contributed to conditions that allowed the parasite to spread.
The outbreak therefore suggests that sovereignty cannot simply mean insulating a country from external influences. Climate change, animal diseases and invasive species are transnational problems. The screwworm case shows that ignoring international environmental challenges does not stop their effects reaching the USA. Instead, protecting national interests increasingly requires international cooperation, scientific coordination and collective action beyond national borders.