Today, I have asked ChatGPT about the New World screwworm (NWS), including how it was in the 1960s-early ‘70s versus what has changed more recently. I normally don’t like to dwell on topics that include flesh-eating larvae—but here you go.

What is the New World screwworm

The NWS is a species of blowfly whose larvae cause obligate myiasis: the larvae feed on living flesh of warm‐blooded animals (livestock, wildlife, pets, and occasionally humans), rather than just dead tissue. CDC+2CDC+2 A female fly lays eggs in open wounds or even in mucous membranes; when they hatch, the larvae burrow into healthy tissue, enlarging wounds, causing severe damage, risk of infection, and possibly death if untreated. usbiotechnologyregulation.mrp.usda.gov+2CDC+2

Eradication in the 1960s–early 1970s

In the mid-20th century, the United States launched a massive campaign to eradicate NWS. Starting around 1957, scientists developed and employed the sterile insect technique (SIT). This involved mass rearing of male screwworm flies, sterilizing them (often via irradiation), then releasing them in large numbers. Because the females mate only once in their lifetime, if that pairing is with a sterile male, no viable eggs result. Over time this dramatically suppressed and then eliminated the wild fertile population. FAOHome+2Office of Research and Innovation+2

By 1966, NWS had been eradicated from the U.S., including the southeast and southwest. screwworm.org+1In parallel, similar efforts took place in Mexico and later in Central America and parts of the Caribbean. By the early ’70s, these were well underway or achieving success in many regions. IAEA+2Office of Research and Innovation+2

The early programs were characterized by huge facility investments, aerial releases of sterile males, intense field surveillance, wound treatment, and strict controls such as quarantine and livestock movement restrictions. The economic benefit was high (livestock savings, lower mortality, etc.). screwworm.org+2APHIS+2

What’s different now (2020s vs. 1960s-70s)

While much remains the same biologically (the fly’s life cycle, obligate parasitism, that females mate only once), several things have changed in practice and in risk environment:

1. Resurgence / spread in Central America & Mexico
   Although NWS was eradicated from the U.S., Mexico, and much of Central America, since about 2023 there has been a notable increase in cases in animals and people in countries north of the old “barrier” zone, including Panama, Costa Rica, Nicaragua, Honduras, Guatemala, Belize, El Salvador and Mexico. APHIS+2CDC+2
2. Barrier maintenance & its challenges
   In decades past, once eradicated in large zones, the program maintained “barrier” release of sterile flies at geographic chokepoints (e.g. Panama) to prevent reinvasion. Now, that barrier has shown signs of weakening; parts of Mexico are seeing outbreaks again. Maintaining barriers is logistically, financially, and politically more complex. APHIS+2Office of Research and Innovation+2
3. Scale & capacity ssues
   The sterile insect technique is still central, but the facilities and fly production have to be larger or at least consistently matched to outbreaks. There is more pressure now to increase production of sterile males and to expand facilities (for example, in Mexico) to respond rapidly. The newer outbreaks stretch resources. Office of Research and Innovation+1
4. Climate, animal movement, surveillance, and blobalization
   Modern risk factors include more extensive animal trade, possibly illegal or informal movement of livestock across borders, and changes in climate and environment which may facilitate reinvasion or expansion. Surveillance and early detection are more critical than ever because small incursions can now spread faster. Also, people are more aware of zoonotic implications (risk to humans) and public health. APHIS+1
5. Technological improvements
   The basic SIT remains, but there is ongoing research into making it more efficient and perhaps integrating genetic modifications or molecular techniques (e.g. sex-specific lethality) to make sterile releases more effective and reduce the number of flies needed. BioMed Central

Summary

NWS remains biologically similar to what it was in the 1960s-70s: same life cycle, feeding behavior, and vulnerability to sterile insect control. What differs now are the circumstances: resurgence in areas once cleared, more complex border and trade challenges, greater logistical demands on SIT programs, and the need for improved, modern tools and surveillance. The success of past efforts shows that eradication is possible — but maintaining that status requires persistent, well-resourced action especially under changing environmental and sociopolitical conditions.