Screwworm re-emergence, illegal cattle movements, and emerging risks to wildlife and protected areas in Mesoamerica

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

New World Screwworm (Cochliomyia hominivorax), eradicated from North and Central America through decades of Sterile Insect Technique programs, has re-emerged across Mesoamerica with alarming speed. Following a surge in Panama in 2023, the parasite spread northward through Central America, reaching Mexico by late 2024. Nearly 100,000 domestic animal cases and hundreds of human cases have since been reported, prompting livestock trade restrictions and significant economic losses. Despite this scale, wildlife impacts have received limited attention.

Here, we collate confirmed and suspected screwworm infestation cases in free-ranging wildlife across Mesoamerica, discuss conservation implications and the role of livestock movements as a main driver of the parasite’s re-emergence, and propose priority One Health planning. We report screwworm myiasis in four Baird's tapirs (Tapirus bairdii) in Costa Rica and camera-trap images from Guatemalan protected areas showing potential screwworm infestation in two pumas (Puma concolor) and an additional tapir. 

Considering historical data, recent modeling, and current conditions in Mesoamerica such as reduced wildlife populations, degraded habitats, elevated livestock densities, and limited veterinary capacity, we argue that this parasite poses a credible conservation threat. Evidence from detection patterns, enforcement outcomes, and documented trafficking routes implicates illegal livestock movements as a key driver of re-emergence and spread. Sustained control will likely require addressing this underlying driver alongside expanded sterile fly release, strengthened wildlife health surveillance, and cross-sector, transboundary coordination. Integrating wildlife into screwworm response frameworks is essential to protect biodiversity, ecosystem integrity, and sustainability of eradication investments.