TAHC holds New World Screwworm training session at JB Wells

Field inspectors with the Texas Animal Health Commission and game wardens with the Texas Parks & Wildlife Department gathered at JB Wells Expo Center in Gonzales on Wednesday, July 9 for a daylong training session about the New World Screwworm that has been found in cattle south of the border in Mexico.

“Thankfully, (the screwworms are) still in Mexico and they haven’t made it anywhere close to us just yet,” TAHC spokesperson Erin Robinson said. “Our team in Austin has been working for about a year now to develop plans and work-through scenarios and really just be prepared for a possible incursion into Texas. In the case they do get here, we can respond effectively and quickly, so that it does not have as many impacts as what it could have.”

Robinson said the training brought TAHC inspectors from across all six regions throughout the state to Gonzales to learn how they would handle livestock in the state if an incursion takes place. TAHC is also teaming up with TPWD, which had game wardens present as they would handle the impact to wildlife, as the screwworm can latch onto any other animal — including deer and birds  — as a host.

Conducting the training was Dr. Thomas R. “TR” Lansford, the TAHC deputy executive director and assistant state veterinarian, who said Gonzales was chosen because of its location in southern central Texas “which historically was an area that was certainly impacted by screwworms.”

“When you look at the distribution of that fly (Cochliomyia hominivorax) over time, prior to eradication especially but even after eradication (in the 1960s), we had some outbreaks in the 1970s in these counties in this part of Texas were impacted,” Lansford said. “If you think about the distribution of cattle in Texas, certainly Gonzales County and some of the surrounding counties are the counties with the most cow-calf operators and the highest population of cow-calf cattle. So we’re trying to gear up to be able to respond efficiently and do everything we can to promote continuity of operations, despite having this pest in in our environment.”

Lansford said the presence of facilities like JB Wells Arena and its show barns as well as Graham Cattle Co., which has its feed yard less than a mile from the Expo Center, and many nearby livestock production operations made Gonzales the “ideal location” to practice getting ready should the screwworm fly find its way across the southern border to Texas, though he hopes they never have to do so.

“Part of our training here is scenario-driven and because you have facilities like this in the area, it makes it very real life to put out scenarios associated with those types of facilities and operations for our inspectors to think through, and for us to think through, about how will we handle this,” Lansford said. “It's been more than 50 years since the screwworm was eradicated from Texas and the United States, and certainly we have a lot of producers that are not aware of the impact that an incursion could have on their operations and animals in their operation, in addition to the wildlife.”

Lansford had inspectors outside practicing catching flies in traps as this will make up the surveillance portion of a three-prong approach to dealing with screwworm flies — the others being treatment by release of sterilized flies and control by keeping infestations contained so they do not spread. Catching flies and identifying non-sterile flies will help field agents know where they will need to release sterilized flies into the environment.

Screwworm females will lay 250-300 eggs in an open wound of a host animal, like a cow, because the larvae need live tissue to feed. These eggs hatch into maggots which cause an infestation, also called myiasis.

These maggots burrow or “screw” their way deeper into the flesh of the host, causing severe tissue damage and the potential for death of the host animal. The larvae then pupate three to seven days after hatching and become full adult flies about a week later. The entire life cycle is just about 20 days.

While males can mate up to 10 times in their short lives, the female flies only mate once and store the sperm of their mate. This is where the sterilization program plays a part in helping prevent the spread, Lansford said. The technique was developed in the 1950s to sterilize an abundant number of male flies and then release them where an outbreak has taken place.

“Because of the biology the screwworm fly, the females only mate once, so if you saturate the environment with sterile males that breed with the natural females, they will be infertile and not reproduce,” Lansford said. “Over time, the generations and the fly population goes down and goes away.

“We’re working with our federal partners to encourage them to increase sterile fly production capacity and develop that capability within the United States and certainly a lot of our stakeholders — industry stakeholders and the USDA — have been working very diligently to try to get that accomplished,” he added.

Lansford said ranchers can look for clinical signs of an infestation as they will notice some kind of wound on an animal that has a very foul odor associated with it.

“That’s one of the hallmark signals or signs of a screwworm infestation is the smell,” Lansford said. “The other thing that we can observe from more of a distance, especially animals that we can't get close to, like wildlife, is those animals may segregate themselves and go to be off alone. They may get worms in their ear canals or sinuses in the soft tissue so they’ll act irritated or exhibit signs like head shaking due to discomfort and pain.”

Lansford said there are products that contain pyrethin and can be sprayed onto animals topically to treat infestation, as well as systemic pharmaceuticals. He said there are also some concoctions that are known to work, but are not approved for use in the United States, so his department is working to get the USDA and FDA to try to get approvals for using those substances.

More training sessions are planned at the JB Wells Expo Center in a few more weeks with livestock inspectors coming to Gonzales as well as people involved with the Texas and Southwestern Cattle Raisers Association, so Lansford said residents should not be surprised to see branded trucks in the community.

“Just to reiterate and re-emphasize again, we're not in a crisis. There are no New World Screwworms in the United States or in Texas right now, but we want to be prepared as well as we can be to deal with that if that eventuality occurs because an ounce of prevention is worth a pound of cure,” Lansford added.