Parasite Control

Urgency in Action: We Must Eradicate New World Screwworm

Tue, 03 Jun 2025 16:14:06 GMT

New World screwworm (NWS) continues to threaten the U.S. cattle industry. The potential impact is devastating — the larvae can kill an animal in just four to seven days if not quickly detected and treated.

Colin Woodall, National Cattlemen’s Beef Association CEO, discussed the hurdles of controlling the spread of NSW on the latest episode of the “Unscripted” podcast .

“We have to eradicate it from here,” Woodall stresses. “We need to eradicate it from Mexico. We need to eradicate it from Central America. We need to push this thing all the way back down to South America.”

The NSW fly and its larvae are flesh-eating parasites that pose a significant threat to warm-blooded animals.

“This is not just a cattle issue,” Woodall says. “This could be dogs. This can be cats. It can get into people. So, anything that is warm blooded could be a host for this flesh-eating parasite.”

Woodall says NSW is approximately 700 miles from the U.S. border, having breached the isthmus of Mexico in the states of Oaxaca and Veracruz, adding that Texas is expected to be the first point of entry if the fly continues to move north.

“We’re going to look at every eradication option possible, because we have to get rid of this thing,” he says. “This is not something that can become endemic to United States. We have to eradicate it from here.”

Woodall says the situation has been complicated by cooperation challenges with Mexico. Earlier attempts to transport sterile flies were hindered by bureaucratic obstacles, with planes unable to land and flies dying before deployment. This led Agriculture Secretary Brooke Rollins to close the border, sending a clear signal to the Mexican government about the need for more serious action.

He explains cooperation has reportedly improved, with USDA teams planning to visit Mexico to assess the current situation. The primary strategy for control involves releasing sterile flies into the wild to disrupt breeding and push the population back southward.

Woodall says NCBA is actively working on several fronts to address the threat:

Pushing for the establishment of a domestic sterile fly production facility.
Exploring genetic engineering technologies for fly control.
Investigating treatment options (such as ivermectin) and helping producers understand how to detect and treat potential infections quickly. Woodall says treatment is possible, explaining ivermectin has proven effective in killing larvae and treating wounds. However, early detection is crucial due to the rapid progression of infection.
Conducting education and awareness campaigns to explain the threat without causing panic. He says misinformation has been a significant challenge. A recent false report about NSW in Missouri caused panic and temporarily impacted cattle prices. He adds that while the threat is serious, it’s not a cause for panic.

“While everybody needs to be aware, they don’t need to panic, and that’s the thing we want everybody to understand,” Woodall summarizes.

NCBA is taking an active role in addressing the threat of NSW through education, technological exploration, government collaboration and a clear commitment to preventing its spread.

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More Than Annoyance: Flies Can Impact Health and Profits

Tue, 06 May 2025 15:16:34 GMT

With fly season approaching, now is the time to evaluate and refine your fly management plan for 2025.

“If your 2024 control efforts underperformed, consider adjusting your approach,” says David Boxler, Nebraska Extension livestock entomologist. “The best control method will depend on several factors including efficacy, cost, convenience and your current herd management practices.”

He also reminds producers that horn flies can migrate from neighboring untreated herds, masking the effectiveness of your efforts and increasing fly pressure. For this reason, Boxer recommends a comprehensive, integrated fly control.

The horn fly is one of the most damaging pests of pasture and rangeland cattle across the U.S., Boxler says in a recent “ UNL Beef Watch .”

“Adult horn flies are blood-feeding insects that take an average of 30 blood meals per day,” he says. “Their populations can build rapidly and often exceed the Economic Injury Level defined as 200 flies per animal. Once fly numbers surpass this threshold, cattle experience reduced weight gain and milk production due to fly-induced stress and altered grazing behavior.”

Observing your cattle during summer months is key to detecting fly pressure. Boxler asks, “Are they constantly tossing their heads, swishing their tails or twitching their skin?”

These signs of fly irritation indicate a more effective control strategy might be needed.

“If you are seeing flies, ticks, lice or insect damage to your cattle herd, we know there is an economic impact; however, that impact can become far greater than production or weight gain loss alone,” says Ashby Green, DVM, Neogen senior technical services veterinarian. “Insect pressure affects grazing patterns of cattle, it affects their comfort and it can lead to health issues. Some of those health issues can be definite, such as anaplasmosis.”

The vectors responsible for spreading anaplasmosis include horse flies, stable flies and ticks. This condition has been reported in most states across the U.S., while the disease has been recognized as endemic throughout the South and several Midwestern and Western states.

“With horn flies, we’re looking at mastitis risk, so that’s going to impact both dairy cattle and also our cow-calf operations,” says Jonathan Cammack, Oklahoma State University assistant professor and state extension specialist. “A lot of times, horn flies will feed on the udders of the animals, and they transfer the Staphylococcus aureus bacteria because they land on the manure, then they go back to the animal to feed and bring those bacteria with them.”

Several other conditions are propagated by flies or ticks, including pinkeye, which can be spread by face flies and causes inflammation and ulceration of the eyes. Pinkeye-affected calves are, on average, 35 lb. to 40 lb. lighter at weaning compared to healthy calves, according to a University of Kentucky report.

Cammack says that due to flies, “We’re looking at probably $6 billion in losses annually to U.S. cattle production, and that encompasses everything from actual loss in production due to decreased weight gain or decreased milk production, veterinary needs associated with treatment of cattle with exposure to pathogens from some of these insects, and then also the control measures associated with managing those individual fly species.”

Ticks present economic risks as well. Cammack says that during a 100-day growing period producers can see a decrease in total weight gain in calves by about 20 lb. For stockers, over that same 100-day period during the summer months, they can experience a decrease in weight gain by about 60 lb.

“With what current prices are, 60 lb. could translate to a significant amount of money returned when we’re talking about the few dollars that it might cost for some tick control,” he says.

(Neogen)

Controlling flies and insects: Tips to implement
Now is the time to take steps to control flies and ticks, as populations emerge with the warmer weather.

In “ Stopping Flies in 2025: Tips to Battle These Economic Pests ,” Cassandra Olds, Kansas State University Extension entomologist, shares four steps to controlling flies

Know what flies you’re dealing with.
Reduce populations.
Eliminate breeding grounds.
Consider chemical control options.

Similar to Olds, Green recommends using a multi-pronged approach to insect control. Fly tags, feed-through insect growth regulator (IGR) products, pour-ons, back rubbers and dust bags can help diminish the population. A pour-on with an IGR destroys the larval development in flies and greatly reduces the fly population. For ultimate control using a pour-on, look to a unique combination of actives within one solution that includes an IGR, an adulticide, and a synergist that supplies relief to cattle from infestations and provides producers with a reliable solution that helps minimize handling, time and labor costs.

“Both back rubbers and dust bags can be highly effective if managed correctly. Keep in mind, when these are put out to withstand the elements, including moisture and rain, it’s key to keep the dust fresh or the oil recharged in your back rubbers. Otherwise, they will diminish in their ability to control flies quickly,” Green advises.

Cammack stresses the importance of accurate dosing by the individual animal’s weight and following label guidelines.

To best control flies and insects on cattle operations, “the easy and effective way is the best way,” Green summarizes. “It’s up to you and with the help of your veterinarian to help create that combination.”

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More Action Needed By Mexico Before Reopening Border for Feeder Cattle Imports, Says Vilsack

Sun, 19 Jan 2025 20:54:32 GMT

A letter sent Friday by outgoing USDA Secretary Tom Vilsack to Mexico’s Secretary of Agriculture Julio Antonio Berdeguê acknowledges the progress made in reopening cattle trade between the two countries following the detection of New World Screwworm (NWS) in Mexico, but says more action is needed to resume trade.

Key developments:

Technical collaboration between U.S. and Mexican teams
Full technical agreement on protocol reached on Dec. 12, 2024
Ongoing work to approve pre-export NWS inspection facilities.

Vilsack emphasizes the importance of expediting the approval process for these facilities to resume safe export as soon as possible, citing the significance of trade for a safe and affordable food supply.

The letter also addresses efforts to combat the spread of New World Screwworm:

Emergency funding has been authorized to increase sterile fly production
Production has increased fivefold in the past year
Enhanced regional response through increased dispersal, surveillance, education, and partnerships
Acknowledgment of Mexico’s partnership in sterile fly releases, movement controls, and surveillance
Shared goal to push the pest south to the Darien Gap

Vilsack requests immediate support from Secretary Berdegué for the establishment of two planned sterile fly dispersal centers in Southern Mexico to strengthen current efforts.

The letter maintains a cordial and cooperative tone throughout, emphasizing:

Shared commitments and goals
Acknowledgment of Mexico’s efforts and partnership
Expressions of gratitude for collaboration
Requests for continued support and expedited action

Industry sources say specific testing will take place Monday, Jan. 20, and that and other tests will go a long way in establishing a trade resumption timeline.

NWS Trade Impacts Started in November
As previously reported, USDA’s Animal and Plant Health Inspection Service (APHIS) suspended imports of live cattle and bison from Mexico on Nov. 22, 2024, following the detection of New World screwworm (NWS) along Mexico’s southern border. This pest can have a significant negative impact on cattle health, and U.S. authorities have been working to develop protocols to screen animals coming into the country.

Several factors are influencing the timeline and pace of reopening:

Facility inspections: Both countries have agreed on protocols, but implementation requires facility inspections and approvals.
Quarantine period: A seven-day quarantine after animal checks
Port readiness: The most important port to get moving again is Santa Teresa, New Mexico.

The temporary suspension of cattle imports from Mexico has had notable effects on the U.S. cattle market:

Reduced supply: About 250,000-300,000 fewer head of cattle are estimated to have been imported due to the suspension.
Price support: The trade disruption has been supporting feeder cattle and calf prices in the U.S.