Missouri agriculture officials tighten livestock protocols amid screwworm threat

JEFFERSON CITY — New World Screwworms are back in the United States, with the insect being detected in Texas on June 3rd.

There are currently nine confirmed animal cases in the United States, in Texas and New Mexico.

Because insects are known to affect wildlife, the Missouri Department of Agriculture is working with local producers to mitigate the potential spread.

“We’ve known it’s been moving up through Mexico for quite a while. So, I think most cattle producers, most people knew that it was a matter of time,” said Callaway County cattle producer Doug Frank of Frank/Hazelrigg Cattle Co.

The CDC defines a screwworm as a “parasitic fly that completes its lifecycle by feeding on the tissue or flesh of warm-blooded animals.” The larvae are also referred to as maggots and have been known to be a larger issue for livestock.

“Right now, we’re talking about it a lot in the context of cattle because it’s a huge pest for the livestock industry, obviously…It’ll cause those wounds to be much deeper and much more intense. And especially if they have multiple wounds, that can be really concerning,” said MU Extension assistant professor and entomologist Emily Althoff.

Althoff says the strategy has been to mass-produce sterile males and release them into the wild.

This method controlled their spread in the past, but she believes budget cuts for those programs, and increasingly, illegal cattle trafficking, allow for the invasive spread of screwworms.

“I think the last time that we had them here in the States was in the 1980s. So, we’ve had quite a long period of time for success with this program…in 2022-2023, that time range, we started to see that buffer zone gets breached,” said Althoff.

Althoff added that past migration patterns led screwworms to Missouri.

This is why the Missouri Department of Agriculture is strengthening protocol and being diligent when it comes to transferring livestock in and out of the state.

“Now there are a lot of movement restrictions that have to be followed and monitored to prevent it from moving about,” said Steve Strubberg, State Veterinarian and Director of Animal Health at the Missouri Department of Agriculture.

The most important thing for ranchers and producers to do is to keep a keen eye out for unusual behaviors or signs of illness in their livestock.

“Just signs of an injured or sick animal. So those animals are feverish, not eating well, maybe acting noticeably different, and so forth,” said Strubberg.

The USDA wants people to know this is not a food safety issue.

The screwworm does not pose a risk to beef consumers.

However, the fly’s larvae can cause infestations in humans and all mammals, including pets, such as dogs and cats.

On June 12, the FDA issued an emergency use authorization for a drug to treat domestic animals with confirmed cases of screwworm.

The drug is generic nitenpyram.