The Texas Farm Bureau posted a video in June on all of its social media channels, alerting ranchers about the approach of New World screwworm (NWS). The video featured a sixth-generation cattleman named Lizeth Cuellar Olivarez, who offered a chilling warning.
"I don't know if people have the stomach for what they're gonna see," Olivarez said. "It's literally an animal being eaten alive."
New World screwworm is a parasite native to the American Southwest that was eradicated decades ago. It comes from the eggs of a specific type of blowfly, called Cochliomyia hominivorax, which loosely translates to 'man-eater.' The fly lays its eggs in the wounds of living creatures. A laceration as small as a tick bite can lure the blowfly, and the resulting larvae will bore their heads into the flesh and eat.
If unnoticed and untreated, it will nearly always result in death.
Before eradication, NWS was an economic disaster for the United States. The USDA estimated that producer losses related to infested livestock in the 1930s and 1940s cost the economy up to $10 million a year. If screwworms return to Texas, the federal agriculture agency predicts losses of nearly $2 billion a year. That cost doesn't only come from treating infested cattle, according to Sonja Swiger, Ph.D., of the Texas A&M University Department of Entomology and Texas A&M AgriLife Extension. Cattlemen would have to change many things about how they operate.
"It does change practices when it comes to how you raise your animals, how you work your animals, when you calve your animals," Swiger said. "And then you have to worry about incidents when they get injured."
Wildlife, pets, and people are also vulnerable to this maggot infestation, which is called myiasis.
In humans, there have been a handful of travel-related cases of screwworm myiasis in the United States over the last decade. These typically happen when a person falls asleep, unprotected, in a place where the screwworm blowfly is endemic.
"So if you get a wound in your nose and you fall asleep in a place where they're located, they'll just go in there and lay the eggs, and you won't even know they did it," Swiger said.
In this episode of Petrie Dish, Swiger details the threat posed by New World screwworm, how to reduce risk, and what is being done to keep the flies at bay.
Swiger and her colleagues at Texas A&M AgriLife Extension Service have provided a New World screwworm fact sheet and a variety of other screwworm resources online. Additionally, a group of livestock, wildlife, equine, and landowner groups has formed a coalition called The Screwworm Coalition of Texas, which has created a clearinghouse of information about screwworm. At its website, you can figure out how to quickly identify the screwworm, report possible infestations, and learn more about this both as an economic issue and a health issue.
