Dr. Lora Bledsoe Explained New World Screw Worm Issues at R-CALF Convention

~Norman Kincaide

Dr. Lora Bledsoe, DVM, serves as Policy Advisor within the Health, Food and Agricultural Resiliency Directorate at the Office of Health Security, Department of Homeland Security. She earned her doctorate in Veterinary Medicine from Colorado State University in 2013. She has over a decade of food animal veterinary practice. Her family raises cattle and quarter horses on the Bledsoe Ranch near Hugo, Lincoln County, Colorado.

Dr. Lora Bledsoe, DVM, R-CALF Convention, Rapid City, South Dakota, June 18, 2026

On June 18, 2026 at the R-CALF Convention in Rapid City, South Dakota, Dr. Bledsoe gave a presentation: Narco-Ranching and New World Screwworm, Protecting Your Herds, Protecting Your Homeland. She first outlined the purpose of the Office of Health Security (OHS), which is to lead and support the Department of Homeland Security to deliver broader, more holistic value to the DHS workforce, individuals in DHS custody and the nation. Food security is national security. In this respect, OHS collaborates with industry, academia, federal, state, local, tribal and territorial partners to build relationships and capabilities to protect the United States health, food and agriculture from intentional and natural threats, which is crucial to national security and safeguarding the American public.

The New World Screwworm represents a threat to American health, food and agriculture. It is an invasive fly whose larvae (maggots) feed on living tissue, affecting all warm-blooded mammals, livestock, horses, pets, wildlife, and humans. Infestations begin in small wounds or mucous membranes, which includes tick bites, cuts, nasal passages, umbilical cord and reproductive tract. Infestations cause severe pain, tissue destruction, secondary infections and is usually fatal if untreated.

The New World Screwworm was eradicated from the United States in the 1960s and much of Central America in the 1980s using the sterile insect technique. This invasive fly has re-established in Mexico with 28,970 total reported cases in animals as of June 15, 2026. The first Untied States case was in La Pryor, Texas on June 3, 2026 in the umbilicus of a new born calf. An additional 12 cases have been confirmed: 8 cattle, 2 goats, 1 sheep in Texas and 1 dog in New Mexico. This is the situation in the last thirty days. No wild flies have been detected (detection is defined as at least one wild fly found in a trap).

The main effort to combat the NWS is through the sterile insect technique. Screwworm pupae are irradiated to produce sterile adult flies. Sterile males are released into the environment to mate with fertile females. The female Screwworm fly will mate only once in her lifetime. When mated with a sterile male she will lay unfertilized eggs. To be effective 500 million sterile flies per week are needed to push back the fly swarm based on historical data. Currently, 100 million sterile flies per week are being produced in Panama. Which are transported to Texas, then released within the dispersal area along the US-Mexican border. There is a sterile fly production facility under construction in Metapa, Mexico, expected completion by the end of 2026. It is expected to produce 30 million sterile flies per week by July 2026 and 100 million sterile flies per week by the end of 2026. A Moore Air Force Base, Edinburg, Texas, facility is under construction with expected completion by the Fall of 2028, with production of 100 million sterile flies per week by the Fall of 2027 and 300 million per week by the Fall of 2028. The Department of Homeland Security is expediting daily shipments of flies in McAllen and Del Rio, Texas ports of entry.

There is a new technique called Novofly. One half of all sterile flies currently produced are female, which are not useful in suppressing the wild fly population. Novofly genetically engineers a strain of Screwworm that stifles female embryos from developing, thus only male flies are propagated. This ensures that 100% of flies irradiated are male, which will result in double the sterile fly production once deployed.

The impact on ranching industry based upon modelling and past experience suggest potential losses up to 3 billion annually if NWS re-establishes in the United States. Heavy impact will be on livestock production resulting in animal loss, production loss, prevention and control cost and movement restrictions. This will also affect international trade and increased cost to federal and local government for control measures.

The impact on wildlife can be devastating. In endemic areas the Screwworm has caused up to 80% death loss in white-tailed deer fawns. This will have downstream effects on hunting and exotic game economies. Working dogs and horses are at high risk due to frequent minor cuts and tick bites and field deployment in brush and rangeland where infested livestock or wildlife may be present. For humans, travelers, ranch workers, hunters, and migrants with untreated or contaminated wounds can develop Screwworm infestations.

Monitoring is essential to stopping the NWS. Ranchers are most likely to first see sick or injured livestock or wildlife. They can provide early warning by photographing lesions, noting locations and notifying state, USDA, or veterinary contacts. The key field indicators of NWS infestations are: strong foul odor of decay emanating from wounds with or without maggots. The presence of maggots in wounds around the nose, mouth, ears and genital regions. Wounds that appear small externally but have extensive tunneling beneath the skin. Irritated or abnormal behavior in animals, such as persistent head shaking, excessive chewing or licking of affected areas and reduced mobility.

Prevention in stopping the Screwworm include recognizing common management practices and life stages that create Screwworm infestation opportunities. These include: branding, dehorning, castration, vaccination, ear tagging, and calving for dam and offspring. To prevent infestations from occurring a variety of medications have been approved for use on NWS, a key difference compared to previous events. Ranchers need to develop a prevention plan with a local veterinarian well in advance of periods of increased risk within ranch operations.

Reporting is also essential to stopping the NWS. This involves sample collection. Cover the area or wound to prevent larvae from escaping. Collect the larvae into a leak proof container and submerge in 70% ethanol or isopropyl alcohol. Do not dispose of live larvae in trash or on the ground. Report an infested animal (livestock, pets, wildlife) to animal health officials immediately and hold the animal for veterinary assessment. For humans, refer the person to a healthcare provider or emergency department immediately. Inform the healthcare provider of travel history and NWS concern. Document location, date, species and any recent movements of animals and people.

Narco Ranching can elevate the risk of NWS advancement. Smuggled cattle typically avoid sanitary inspection and traceability. This increases the chance of NWS infested animals moving undetected, thus expanding the infested region. Fraudulent ear tags and paperwork complicate trace back if NWS is detected in US herds. The same logistical networks used to move contraband cattle also support drug, currency and weapons trafficking. This results in border regions that face combined pressures of transnational crime and animal disease threats impacting land, wildlife and community safety.

Cattle laundering occurs when contraband cattle are moved to collection points near the Mexican Guatemala border where ear tags are obtained through corrupt officials or third parties who report an excess number of cattle. Central American cattle with no ear tags, health documents or transit permits are smuggled across the border and brought at collection points. Personnel at collection points sell ear tags to traffickers for almost 10 times the legal price. These ear tags register the cattle with approved production units. From there traffickers obtain or falsify sanitary certificates and travel permits from corrupt officials. Ranchers buy these cattle that now appear to have originated in Mexico and can then sell them to meat companies.

Livestock are also used in drug trafficking operations. Livestock trailers are used as concealment environments where strong organic odors and crowded conditions can challenge canine detection of narcotics. Cattle can be used as drug mules by forcing packages into the animal’s stomach via the mouth. Surgical implantation is also used to conceal contraband in the abdomen of the animal leaving a small surgical scar. Ranchers operating on or near the border may encounter suspicious livestock loads, trailers with unusually strong odors and animals with unexplained surgical scars.

The current situation with the NWS is complicated and urgent. Methods are being implemented to push back the infestation. The NWS is a warm climate insect and will only advance farther into the United States according to a summer time schedule. Cold temperatures will inhibit advancement farther north. It remains to be seen how effective the measures taken now will affect the current NWS infestation. The current NWS is a national security issue that impacts agriculture, food and health security.

Source: Dr. Lora Bledsoe, Narco-Ranching and New World Screwworm, Protecting Your Herds, Protecting Your Homeland.