NC Ag Commissioner addresses New World Screwworm situation in op-ed

Source: NCDA&CS

‘From the tractor’ is published in the monthly Agricultural Review. This column appears in the July 2026 edition of the paper. For the most up-to-date information about New World Screwworm, visit our website at Veterinary – New World Screwworm | NC Agriculture.

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JULY 6, 2026 - Recently, the United States had its first detection of New World Screwworm in a calf in Zavala County, Texas.

Some of us that have been around long enough may remember our parents or grandparents dealing with New World Screwworm in the 1950s and earlier. It was not eradicated from the Southeastern United States until 1959.

According to USDA, the NWS can infest livestock, pets, wildlife, occasionally birds, and in rare cases, people. Image credit - USDA

This is a serious pest that affects livestock, pets, wildlife, and, less commonly, people and birds. Adult NWS flies can look very similar to houseflies, and the maggots (larvae) look similar to our native fly larvae. It requires laboratory identification to identify larvae accurately.

The NWS larvae feed on the living tissue of warm-blooded animals and cause extensive damage to wounds by feeding on this healthy tissue. While this pest can infect any warm-blooded animal, 60 to 70% of reported cases from the outbreak in the US and Mexico so far are in cattle. Of those cases, umbilical infestations are very common depending on the time of year and calving season.

NWS can infect the smallest lesion – as small as a needle stick or tick bite. An infestation can be fatal within one to two weeks if left untreated but if discovered early then it is highly treatable.

The best cure is prevention – this includes routine inspection for maggots, fly and tick prevention strategies, and management changes for birthing season. We’ve put a link at www.ncagr.gov which has additional ways to monitor for New World Screwworm.

The current outbreak has been a problem in Mexico the past couple years and we have been monitoring the outbreak very closely.

The most promising intervention strategy for New World Screwworm is the release of sterile flies. Female flies mate only once in their lifetime, so mating with a sterile male fly helps fight population growth, and it is how we pushed this pest out of our country in the 50s and 60s.

Currently, there is just one sterile fly production facility located in Panama, but many of these flies are being dispersed from a facility in Texas. The Panama facility can produce about 100 million flies per week, which, is not enough to control this outbreak.

This summer we anticipate another sterile fly production facility opening in Chiapas, Mexico that will add to the sterile flies for dispersal. As this facility comes online and production ramps up, it is hoped this facility will also be able to produce 100 million files per week by the end of the year.

By the end of 2027, a third facility should be producing 100 million more sterile flies per week at Moore Air Base in Edinburg, Texas and it will ramp up to 300 million per week by the end of 2028.

This means that by the end of 2028, there is the potential production of 500 million sterile flies a week, which is what it took to help eradicate this pest the last time.

Our Veterinary Division is working with other states and our federal partners to monitor New World Screwworm and we are hopeful that with animal movement restrictions we can keep this pest from progressing East and North. We will need our producers, veterinarians, and federal and state officials working together to help us monitor our livestock and companion animals and, most importantly, report any suspected cases.

We don’t know the odds of this making it to North Carolina. My hope is that the knowledge we gained from the 1950s and 1960s and our continued collaboration and vigilance will help us eradicate New World Screwworm before it has the opportunity to spread further.