Illegal cattle trade brings New World Screwworm to wildlife and continues to destroy protected areas in Mesoamerica
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Abstract
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.
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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.
https://doi.org/10.32942/X2K05S
Agriculture, Animal Diseases, Animal Sciences, Biodiversity, Entomology, Life Sciences, Other Ecology and Evolutionary Biology, Parasitic Diseases, Parasitology, Public Health, Veterinary Preventive Medicine, Epidemiology, and Public Health
New World Screwworm, screwworm, wildlife, Health, cattle, traffic, illegal, deforestation, mesoamerica, Monitoring, Surveillance, wildlife, health, cattle, traffic, illegal, deforestation, Mesoamerica, monitoring, surveillance
Published: 2025-07-30 19:48
Last Updated: 2026-02-26 09:22
CC BY Attribution 4.0 International
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Language:
English
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