REDFIELD, Iowa (DTN) -- As New World screwworm (NWS) continues to be a problem in Mexico and inches closer to the Texas border, entomologists say it's best to be proactive and prepared for the pest to enter the U.S., rather than reactive if it does get here.

"We need all livestock owners to know how to manage their animals, maintain their facilities and treat any animals for prevention or if they think they have a NWS problem," said Phil Kaufman, head of the Department of Entomology at Texas A&M University. Kaufman, along with colleague Sonja Swiger, livestock Extension entomologist at Texas A&M University, were part of the ongoing SowBridge webinar series sponsored by swine Extension educators at several major universities to discuss timely, relevant topics.

THE PEST

Swiger said the NWS fly will feed on live flesh of warm-blooded animals, especially livestock, wildlife and pets. This can also include humans but is rarely seen on birds. "It is rare to see adult flies. The NWS fly is usually only around when laying eggs on a host," she said. "The flies prefer to be in warmer wooded areas."

NWS flies tend to not travel over large bodies of water and don't travel long distances often, which is why Swiger said the movement in Mexico has most likely been mostly on animals. These flies are also most active between 64.4 and 91 degrees Fahrenheit. The location is also usually in higher rainfall areas of 59 inches per year or more. "These flies don't thrive well in cold or windy areas," she added.

While the NWS fly only has a 21-day lifecycle, as many as 300 eggs can be laid in a wound and hatch within 12 hours.

"The larvae feed on living flesh and don't feed on dead or dying flesh," she said. The animals most susceptible to infestation are newborns through their umbilical cord. The older animals are infested through wounds as small as a tick bite. Swiger said these animals tend to die from a secondary infection or sepsis.

"Even though this is an infection of an animal and is not contagious, it's still considered a foreign animal disease due to location and restrictions," she added.

Kaufman said the spread in Mexico has been by affected animals moving north, usually illegally.

Mexico has worked with the USDA's Animal & Plant Health Inspection Service to develop protocols for moving animals. "The protocol includes treating the animals with Ivermectin three days before movement, inspection before departure and a certificate of inspection issued, and then inspected again when off loaded," he explained.

Surveillance is also an important part of knowing where the NWS flies are. This is done through traps that attract flies. Once trapped, the flies are inspected to determine the type captured. If one looks like an NWS fly, it is put in a container to be further identified. No NWS flies have been found in the U.S.

Kaufman said wildlife continue to be a challenge as they aren't as easily contained. He recommends anyone seeing suspicious wildlife to report them to their local wildlife department.

HAVE A PLAN

Eradication is the ultimate goal, but this takes cooperation among many people through surveillance, monitoring, inspecting and reporting.

"If NWS does become a problem in the U.S., it's important for livestock owners to think about how they will manage their animals. This includes tail docking, ear notching, castration, dehorning," Kaufman said. "Do these things need done and when."

He said it will also be important to maintain facilities to avoid cuts and scratches. Breeding and birth timing will need to be thought out. Even vaccinating animals could cause an injury or wound, which could be infested by larvae.

"All livestock producers need to have a good relationship with their veterinarian and have necessary products on hand if a problem should occur," he added. "But we also don't want to overtreat have a chance of resistance to some of the medicines."

Kaufman said animal owners should expect animal movement restrictions. "We have learned lessons from what we've seen in Latin America. Well-managed operations have fewer issues but still need to be cautious and inspecting their animals."

The sterile fly technique has been the best way to control the spread with the release area moving into parts of Texas to help with prevention. "Sterile flies are produced in a tightly controlled process and have been used for many years. They have it down to a science," Kaufman added. He said more research is expected in the future on the process, including evaluation and mating studies done on the sterile flies that are currently released to ensure efficacy.

Treatment protocols are important to help control NWS flies. Very few medicines are currently approved for use on treating the pest. He suggests contacting a herd veterinarian to develop the proper treatment plan.

For more information, visit: https://agrilifeextension.tamu.edu/….

Also see: "Sterile Flies Combat NWS Spread," https://www.dtnpf.com/….

Jennifer Carrico can be reached at jennifer.carrico@dtn.com

Follow her on social platform X @JennCattleGal

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