The New World screwworm, a parasite native to Central and South America, lays eggs on live animals, causing maggots to eat the flesh and eventually causing an animal's death has been spotted in Mexico. 

For hunters and ranchers in West Texas, this means closely monitoring animals to ensure the deadly parasite does not begin a campaign through Texas. Daniel Suiter, an Orkin Distinguished Professor of Urban Entomology at the University of Georgia, told the Reporter-Telegram that while the threat of a potential outbreak could occur during the spring and summer, the parasite can still survive during the winter months. 

"There's always a little winter die-back of many insect populations," Suiter explained. "But (screwworms) have ways of overwintering and surviving the winter. Many insects are adapted to surviving winter conditions." 

Suiter described the screwworm as being more suited to tropical climates such as the regions of Central and South America, but he said he was unsure of how the screwworm would function within this region. 

According to the U.S. Department of Agriculture, the only way to combat the pest is by dropping sterile male flies from airplanes over large areas. Female screwworm flies mate only once during their life cycle, which creates a pathway for the sterile male flies to lead to a die out within the populations. 

The way that screwworm infestations can potentially infect domesticated livestock and wild animals are when a female fly lays her eggs on an animal's open wounds or other areas such as the animal's eyes or mouth. Any warm-blooded animal — even humans — can potentially be affected. 
Eventually, the eggs hatch into the larvae that feast on the living animal and thus infecting the flesh of the animal resulting in death. 

The screwworm was previously eradicated from the United States via several programs introduced in the 1970s. 

According to a recent article by the Texas Tribune, the screwworm was officially declared eradicated from the U.S. in 1966, but Texas experienced an outbreak in 1976 affecting approximately 20% of cattle.

Suiter said the lab located in Panama that hosts the sterile male flies is still maintained by the USDA's Animal and Plant Health Inspection Service (APHIS). 

"The lab in Panama is still active," he said. "And they can radiate millions of flies a week. That is the best, and the only, option we have." 

Suiter emphasized the importance of reporting any suspicious cases to county agents and highlighted the need for vigilance among hunters and cattlemen. He noted that the parasite can affect various animals but is more common in cattle and deer.

"Reporting to local county agents or wildlife persons or something of that sort so they can run it up to the USDA, and then USDA can take action," he told the Reporter-Telegram. 

Michael Nickell, a museum scientist from the Sibley Nature Center in Midland, said he remembers when the screwworm was officially considered eradicated within the U.S. 

"It's a pretty nasty insect to deal with," he said. "Even though it is officially eradicated, they don't respect borders." 

Additionally, he said for wildlife populations, it can lower the resistance of animals while also succumbing to other known diseases. 

"Specifically, the whitetail deer, especially in Texas, were affected by the screwworm," he said. "When the screwworm was eradicated, it was a check and balance on the deer population, as well, due to the overpopulation of these animals." 

Source - https://www.mrt.com