Illegal cattle trade brings New World Screwworm to wildlife and continues to destroy protected areas in Mesoamerica

Lucy Keatts, Luis Guerra, Jeremy Radachowsky, Jorge Rojas-Jiménez, Rony Garcia-Anleu, Jonathan Pérez-Flores, Chris Walzer, Diego Montecino-Latorre

The New World Screwworm (Cochliomyia hominivorax; “screwworm”) is a parasitic fly historically endemic to the Americas. Females lay eggs in open wounds of warm-blooded animals, including humans. The emerging larvae feed on the host’s living tissue, often resulting in severe damage and potentially death.
After five decades of coordinated efforts, the screwworm was successfully eradicated from North and Central America by the early 2000s. However, it reemerged in 2023, spreading across Mesoamerica and southern Mexico. Almost one hundred thousand domestic animal infestation cases and hundreds of human cases have been reported in this region as of July 2025.
Wildlife has also been affected. We report confirmed infestations in Tapirus bairdii (Baird’s tapir) in Costa Rica and a probable infestation in a Puma concolor (puma) in Guatemala, and outline additional wildlife cases reported in official and non-official sources. Given the ongoing decline of wildlife populations and regional ecological conditions in Mesoamerica, the parasite could be catastrophic for biodiversity in this region. It is urgent to establish coordinated monitoring of cases in wildlife, assess screwworm consequences in these populations, and adjust conservation plans as needed.
Documented cattle trafficking routes that allow evasion of sanitary control points have likely played a central role in the parasite’s resurgence by fast-tracking movement of larval stages across Central America. We summarize previously described connections between cattle trafficking networks, narcotrafficking, habitat destruction, and deforestation of natural habitats, including protected areas in this region, and discuss their link with wildlife health through the screwworm. Urgent action is needed to halt cattle trafficking in order to control screwworm spread, prevent the introduction, propagation, and spillover of other high-risk pathogens into wildlife populations, and safeguard regional biodiversity conservation objectives.