Screwworm
posted on
July 7, 2026
If you've been party to any news feeds over the past month, you're aware that the dreaded screwworm has re-entered the U.S. from Mexico. The USDA is aflutter over this supposed catastrophe, closing all 12 points of entry to the U.S. from Mexico.
As far as we know, screwworm was eradicated from the U.S. in the 1960s with a massive campaign of insecticides. But like all things attacked by chemicals, the screwworm figured out a way to survive, re-migrate, and it's now the subject of massive government outlays.
Screwworm is the larval stage of a certain type of fly. We all know about maggots. The difference with the screwworm maggot from most others is that it will eat not only dead flesh, but also burrow in and consume live flesh. That makes it especially harmful.
The current lines of defense orchestrated by the USDA is to close the U.S.-Mexico border to livestock transfers and then to invest billions of dollars in laboratories to release sterile flies. The screwworm fly mates only once, so if the female mates with a sterile male, she never lays eggs. How's that for an exciting reason to live? Ha!
In cases like this, what is the Polyface response? We don't use chemicals and we wish USDA didn't even exist. What is our answer to something seemingly as devastating as the screwworm?
It may not surprise you that our answer is the same as it is for avian influenza, African swine fever and generally all the maladies that excite pharmaceutical and chemical companies in the agri-industrial complex. The answer is good management, nutrition, and sanitation.
The most vulnerable cattle are in feedlots. I don't know if the three U.S. cases registered so far were in feedlots; the USDA keeps these kinds of statistics under close wraps. Feedlots are notoriously filthy with built-up manure--the cows live in their toilet. With so many animals crammed together, it's an ideal host environment for pathogens, who don't have to work very hard to find hospitable landing sites. In addition, animals with wounds attract the flies for a point of entry; feedlots are notorious candidates for bumps and bruise due to tight fencing and close bullying.
The most critical foundation for livestock immunology is minerals. Pre-European land management involved frequent fires, both natural and human-started. These left ashes and charcoal in their wake, which released copious amounts of minerals to the landscape and attracted the native animal population. Within hours of fire passing through, burned over areas re-populated with wildlife seeking minerals. Bison licked charred trees to ingest enough minerals.
In today's farming and ranching protocol, with fire suppression a major objective and animals locked in certain areas, good management requires that we present animals with supplemental minerals. At Polyface, we probably spend three times the money per animal on good minerals as surrounding conventional farmers. That's how we can grow tens of thousands of animals without a vet bill.
The questions I would ask about these screwworm U.S. outbreaks are these:
1. Was it in a feedlot?
2. What kind of minerals are you feeding?
3. Are you moving your animals daily to fresh pasture and therefore away from flies?
4. Are you looking at your flocks and herds every day to observe problems?
5. Are you propping up weak genetics with antibiotics and vaccines?
These questions will never be asked.
Unlike most conventional farmers and ranchers, here at Polyface we do not walk around in a paranoid fear-stupor every day worried about what malady may attack next. That's the mentality of the great majority of American agriculture and certainly it defines the persona of the USDA.
Instead, we walk in faith that nature's default position is wellness and if our animals are not well, it's not due to some nefarious wild conspiracy; it's because we failed in sanitation, genetics, management, nutrition, and comfort.
The number one determinant of robust health is stress. That stress can come from being old, too hot or too cold, drinking poor water, living in filthy conditions, being afraid (especially of bullies in a tight space), and eating a poor diet. To be sure, feedlot beef is not eating anywhere close to the diet an herbivore would naturally enjoy in the wild. It's formulated with carbohydrates to pump them up and contains only a couple of feedstocks rather than the diversity enjoyed in a healthy perennial pasture.
I'm writing this blog to allay concerns among our patrons regarding these perpetual fear-inducing broadsides from the media and the USDA. At Polyface, we are not immune to biological realities. In 65 years, we've had about six significant disease outbreaks, but every single one was caused by us. We violated one of those requirements listed above and nature told us about our mistake.
We do not believe health comes from a needle, a drug, a lab. We believe nature's default position is wellness, and if something is out of kilter, it's our fault and we need to figure out the ultimate cause. But a multi-billion dollar sterile fly release does not deal with why screwworms attacks this animal instead of that one. In light of AI, data centers, and the seemingly endless capacity to amass information, the shallowness of the conventional mindset is truly profound.
In conventional parlance, to question feedlots is to desire starvation. To question Tyson chicken houses elicits howls of "we can't feed the world." To question hog factories like Smithfield is to embrace 1910's hog cholera from muddy, moon-scape pig pens.
The result of this mindset is the cure can only be offered within the boundaries of the question. If you can't imagine a different paradigm, you can't ask a question about it. As a result, our conventional food system remains mired and shackled to chemical band-aids instead of real solutions. At Polyface, we look for primal causes, real solutions, and we're forever grateful that your patronage enables us to continue the quest. Thank you.
