NEW YORK, NY, July 2, 2026 — A newly published study in Conservation Biology warns that efforts to control New World screwworm will be weakened if governments focus primarily on legal livestock production systems while overlooking illegal cattle movements, wildlife, protected areas, and remote landscapes where infestations can go undetected.

The paper, “Screwworm re-emergence, illegal cattle movements, and emerging risks to wildlife and protected areas in Mesoamerica,” was authored by scientists from the Wildlife Conservation Society (WCS) and partner organizations. The study highlights how illegal and unregulated cattle movements remain an under-recognized driver of regional screwworm spread while also creating exposure risks for wildlife populations and protected areas that often fall outside traditional surveillance systems. 

New World screwworm is a parasitic fly whose larvae feed on the living tissue of warm-blooded animals. It can affect livestock, pets, wildlife, and, more rarely, people. The paper comes as U.S. officials respond to confirmed New World screwworm cases in Texas and New Mexico and seek to prevent further spread. Current response efforts include the release of sterile male flies that mate with wild females but produce no offspring, a technique that helped eradicate New World screwworm from the United States in the 1960s and 1970s.

Many corridors used for illegal cattle movement pass through or alongside protected areas, creating opportunities for screwworm to reach wildlife populations that are rarely monitored. Illegal cattle production and trade are leading drivers of deforestation and habitat degradation in Mesoamerica, placing additional pressures on wildlife populations already facing multiple environmental stressors. Although the population-level impacts of screwworm on wildlife remain poorly understood, the authors note that infestations have been documented in species of conservation concern and that insufficient wildlife surveillance limits understanding of potential consequences for biodiversity, ecosystem functioning, and conservation outcomes.

“Much of the discussion around screwworm has understandably focused on livestock production,” said Dr. Lucy Keatts, Associate Director of WCS’s Health Program and lead author of the study. “Our study highlights two additional gaps: the role of illegal cattle movements in facilitating spread and the limited information available on wildlife infections and impacts. Addressing both will be important for effective long-term control.”

The study documents confirmed, probable, and suspected wildlife infestations in Mesoamerica, including cases involving species of conservation concern. Because wildlife are not routinely inspected like livestock, infections may persist undetected in remote areas, limiting the effectiveness of surveillance and response efforts.

The authors warn that protected areas can become surveillance blind spots despite serving as important reservoirs of biodiversity. They argue that wildlife-health monitoring should be incorporated into national and regional screwworm response plans as part of a broader One Health approach linking animal health, ecosystem health, and human well-being.

Added Rony García-Anleu, Director of the Biological Research Department for WCS Guatemala and a co-author of the study, “We have been monitoring wildlife populations since 2004 using camera traps in this area. We have seen wounded animals before, but these types of lesions started only after screwworm arrived to the country.” 

“The risk is not that wildlife are driving the outbreak,” said Dr. Chris Walzer, Executive Director of WCS’s Health Program and a co-author of the paper. “The risk is that we lack sufficient information on where infestations are occurring, how long they persist, and what impacts they may be having in wildlife populations. Stopping illegal cattle movement remains essential, but a serious One Health response must also include wildlife-health surveillance, protected-area monitoring, and information sharing across sectors and borders.”

“Sterile flies were successful, but now they will probably need our help,” said Dr. Diego Montecino-Latorre, WCS Health Program scientist and co-author of the paper. “Today, there are several times more cattle in Mexico and Central America than there were during the original eradication campaign, providing abundant opportunities for screwworm to persist and spread. We will need effective surveillance to tell responders where the risk is moving. Camera traps, field patrols, hunters, veterinarians, and wildlife-health networks can help turn scattered observations into an early-warning system.”

The authors emphasize that wildlife should not be scapegoated as the source of the current crisis. Instead, they argue that wild animals can serve as victims, sentinels, and indicators of where screwworm risk may be emerging. Substantial knowledge gaps remain regarding population-level and ecosystem-level consequences, and improved wildlife surveillance would support both disease-control objectives and conservation decision-making. 

The study calls for stronger coordination among livestock, wildlife, conservation, public-health, and law-enforcement agencies to improve surveillance and response. The authors argue that New World screwworm is inherently a One Health challenge, requiring collaboration across sectors to understand transmission dynamics, identify emerging risks, and implement effective control measures.

"We cannot effectively manage what we do not measure," Keatts said. "Improving surveillance in wildlife and protected areas would help us detect infestations earlier, better understand their impacts, and support more effective regional control efforts. That will require stronger coordination across animal health, wildlife, conservation, and law-enforcement agencies, because no single sector can address this challenge alone."

About the Study
The paper, “Screwworm re-emergence, illegal cattle movements, and emerging risks to wildlife and protected areas in Mesoamerica,” was published in Conservation Biology. Authors include Lucy Keatts, Luis Fernando Guerra, Jeremy Radachowsky, Jorge Rojas-Jiménez, Rony Garcia-Anleu, Jonathan Pérez-Flores, Chris Walzer, and Diego Montecino-Latorre.