Mexico to US Livestock Trade halted due to Screwworm spread
128 comments
·August 9, 2025neutered_knot
ajmurmann
Why is it "used to be"? I've heard about the program before and thought it was incredible. What happened to it?
Edit: Brief research tells me the screwworms broke though to Mexico in November 2024 after cases started increasing north of the Darian Gap throughout 2023 (https://www.aphis.usda.gov/news/program-update/new-world-scr...). It does seem like the funding now is happening through USDA rather than USAID (https://www.aphis.usda.gov/livestock-poultry-disease/cattle/...) and there likely was a funding gap. As much as I like to blame the current administration for defunding USAID the breakthrough happened earlier.
throwup238
Funding was recently cut but this infestation has been building for years. The key failure that caused this current outbreak was during COVID. The lockdowns shut down both the release flights by the US and the mosquito breeding facilities in Latina America, grinding the whole pest control program to a halt.
Noumenon72
Someone must have decided they weren't "essential". Big mistake.
jfengel
Yeah, it got cut back in March.
https://kbhbradio.com/usda-cuts-budget-staff-for-animal-dise...
Part of it was restored a couple of months later.
zahlman
> Brief research tells me the screwworms broke though to Mexico in November 2024 after cases started increasing north of the Darian Gap throughout 2023
Elsewhere in the thread people have posted explainer videos (of how the program works) from 2024 that seem entirely unaware of any such breach.
tomrod
[flagged]
ajmurmann
I have no idea. It certainly seems insanely careless to me to defund something like this but I haven't found anything in my brief research that gives me an idea of the impact. Intuitively I'd expect that to show up in the data a little later (assuming that data is still being collected)
cogman10
DOGE. It was ran by USAID.
VladVladikoff
It was failing long before this. The border used to be down by Panama.
smallmancontrov
Elon was the real screwworm all along.
treetalker
Make America Grubby Again
JKCalhoun
Great (gross) video from the Department of Energy (1960) on how the screwworm was defeated: https://youtu.be/QFoOnS6CWSI
neom
I'd never head of screwworm before, turns out it's not a worm, this page is pretty decent: https://cr.usembassy.gov/sections-offices/aphis/screwworm-pr...
"A screwworm infestation is caused by larvae of the fly Cochliomyia hominivorax. These larvae can infest wounds of any warm-blooded animal, including human beings. The screwworm fly is about twice the size of a regular house fly and can be distinguished by its greenish-blue color and its large reddish-orange eyes.
Infestations can occur in any open wound, including cuts, castration wounds, navels of newborn animals, and tick bites. The wounds often contain a dark, foul-smelling discharge. Screwworm larvae distinguish themselves from other species by feeding only on the living flesh, never dead tissue. Once a wound is infested, the screwworm can eventually kill the animal or human, literally eating it alive." - Sounds great.
mc32
The key to managing this pest [edit: after it breaches the isthmus program] is through active monitoring, treating infested wounds as well as conducting castration and dehorning in less active months. It’s not like cattle herds didn’t exist prior to the 1950s.
tptacek
That's in fact not how screwworms are managed; the "border" of screwworm prevalence was managed by spreading sterilized male screwworms.
mc32
That’s how we manage them now. I mean before we had that program, we dealt with the pest/infestation that way and we can in the future too if need be to combat what’s getting through. Obviously neutralizing them down in the isthmus is preferred but we’re seeing them come up from Mexico now. So if you have a minor infestation that’s how you treat it to address whatever gets missed by the sterilization program.
It doesn’t render the cattle or meat from the cattle useless. Obviously if affected cattle are untreated they will succumb to pest.
nabla9
‘Man-eating’ screw worm turns hospital into horror show https://www.telegraph.co.uk/global-health/science-and-diseas...
Mexican Livestock halted while US is in trade war with Brazil (21 percent of all US beef imports).
grej
The US successfully eradicated screwworms here in 1966 with a brilliant integrated sterile insect technique - I think the very first use of it (and had previously funded helping other countries control it also). But if we had another outbreak spread, I doubt there's any shred of competence left in this current gutted federal government to do anything like that again. Maybe they can have the new ICE folks try to deport the screwworm flies.
luketaylor
The current plan was announced here a few weeks ago: https://www.usda.gov/about-usda/news/press-releases/2025/06/...
jfengel
They announced funding to do it again, back in June. But I have no idea if there's anyone around to pay.
superxpro12
Lead times are asymmetric.
Bender
Whether your meat comes form South America or the US or the EU, always wear gloves when handling raw meats and don't touch your face. There are thousands of types of dangerous larvae that can infect via the eyes rubbing the eyes or the nose picking ones nose when handling raw meats and vegetables. Cutting meat slices thinner and cooking them well kills larvae. Marinating meats with something that contains acetic acid also helps. Stomach acid takes care of the rest.
Beware of the fear porn spreading around this issue. I have already seen articles posted showing what happens when rubbing ones eyes or picking ones nose after handling raw food and of course it is horrific but screw worms are just one of many real risks. Food handlers in first world countries are taught not to touch their faces and to wear gloves among many other safety practices with raw meats and vegetables. Everyone both vegetarian and carnivore unknowingly eat many types of larvae, bacteria, mold, fungus and insects all the time.
I know I will get beat up for going against the agenda but I am that guy.
Aurornis
> I know I will get beat up for going against the agenda but I am that guy.
Food safety with raw meets isn’t really going against the agenda.
renewiltord
What's with everyone saying they know some secret that everyone else is trying to suppress?
Is it just that we all spend time in our bubble and take that to other groups?
I don't even know what agenda he's going against by saying one should be careful around raw meat. Who's on the other side of this?
cogman10
USAID was in charge of the program which monitored screwworm spread in central and south america. The way you combat screwworm is by releasing sterile male flies in screwworm outbreak areas.
LMYahooTFY
Do you have a source? Because this appears to be false. I can't find anything indicating it was funded by USAID.
Everything I'm reading says it has been funded by USDA, and in fact funding has been significantly increased during 2025.
cogman10
https://www.agri-pulse.com/articles/22636-bird-flu-screwworm...
USDA manages the production of the sterile flies. USAID was a major funding source for the UN Food and Agriculture Organization which did the monitoring.
nnutter
I appreciate you citing the USAID funding but you seem to be trying to prove a point rather than get to the truth. Screwworm detection and prevention was not halted because of the USAID shutdown, USDA is actively working on it, one can see this by going to usda.gov and searching for "screwworm". I really appreciate ajmurmann's edit which acknowledges this.
mkoubaa
I don't see why a trade group of affected industries can't collectively fund this
paganel
[flagged]
drhodes
A recent, relevant video from Kurzgesagt: How Nuclear Flies Protect You from Flesh-Eating Parasites https://www.youtube.com/watch?v=zxq60I5RSW8
raaron773
I was wondering where i heard the term screwworm before!
null
erredois
Coming from a family that has cattle and dairy cows in south eastern Brazil, where screwworm is endemic, I was surprised when I listened to a podcast about screwworm, and some of the descriptions about how huge the problem was in the US. After some research it appears it affects more climates that are always hot and humid, and big operations where the animals are not being checked frequently. Also the handling at the 60s was probably much worse than modern techniques for avoiding animals being hurt and treating when they are infected.
Aurornis
> I was surprised when I listened to a podcast about screwworm, and some of the descriptions about how huge the problem was in the US.
It’s not a huge problem in the US. We eradicated screwworm in the 60s.
We are trying very hard to keep it out. The US normally works very hard to monitor and prevent these situations in trade partners.
https://www.scientificamerican.com/article/flesh-eating-scre...
Glyptodon
One more thing where we're going back in time. Sure seems like a new decline and fall is coming bit by bit.
amoshebb
Some folks are posting about the regular flights over Panama, and I’ve seen talk about ending screwworm with a “gene drive”, but I also feel that it doesn’t feel necessary.
But a third option I don’t see talked about a lot: finish the job. We could drop sterile flies all over the USA and Mexico all the way into panama with 1950s tech. We have drones now, surely some inexpensive paper planes shoved out of the back of hercs could cover roughly all of south america for fairly cheap.
throwup238
There is no finishing the job. Screwworm flies have tons of reservoirs in the jungles of Central America that aren’t practical to eliminate for logistical and ecological reasons. We can only control the population in agriculturally important areas by constantly releasing the sterile male flies every year. Whenever we stop the releases, the flies bounce back in a few years.
rdl
The durable reservoirs are in South America, not Central America. We actually eradicated it (at least essentially) all the way down to the Darien Gap.
jeff_lee
Feels like we had the cure in our hands and just let the disease walk back in.
A story from 2020 about how effective the US funded anti-screwworm program used to be.
https://www.theatlantic.com/science/archive/2020/05/flesh-ea...
Archive link: https://archive.ph/3sD9d