New Mexico State Public Health Veterinarian Dr. Erin Phipps speaks with KC Counts about screwworms and how they infect livestock and people.
KC Counts:
I'd like to talk today, Dr. Phipps, a little bit about the impact of screwworm in our region. We'll start by having you tell us just a little bit about what it is and what the harms are.
Dr. Erin Phipps:
So, screwworm is the larvae of a fly that actually used to be present in the United States up until the 1960s. What makes this different from other fly larvae or maggots is that this one feeds not on dead flesh, but on living flesh. So, part of the fly, many flies' natural life cycle, is that they lay eggs in typically dead animals or dead flesh. And that's the maggots that you might see on some roadkill, for example. This fly, the larvae only eat living flesh. So, they lay their eggs not on a dead animal, but on a wound of a living animal. And this wound can be as small as a tick bite, so it does not take a large gaping wound to attract these flies. The fly, as part of their life cycle, lays eggs in open wounds. Those eggs hatch within a day or so. and develop into larvae, which will actually burrow down into the flesh. And so they can cause a small wound to become much larger, very painful, and not able to heal. This is most common in livestock, but it can affect any warm-blooded animal, including humans, including dogs, cats, birds, any sort of wildlife, any warm-blooded animal.
KC Counts:
What can you tell us about what the situation is right now?
Dr. Erin Phipps:
Yes, so currently we're keeping a close eye on the situation in Mexico. Screwworm has been traveling N from Central America and reached Mexico in November of 2024.
KC Counts:
And so, what would your office be on the lookout for?
Dr. Erin Phipps:
Yep. So I work very closely with our New Mexico Livestock Board. They are in charge of surveillance, prevention and control of screwworm in animals. My office, as part of the Department of Health, focuses on the human risk. So really, this is a public health issue.It affects both animals and humans, so we communicate regularly to keep each other informed. They're doing a lot of work preparing for the possibility of animal cases in New Mexico. On my side, as the state public health veterinarian, my role is to focus on zoonotic diseases or diseases transmitted from animals to humans. And this is an example of a zoonotic disease. So, we have worked closely with our state public health laboratory to make sure that we're prepared to receive samples of larvae for identification. We're also doing some preliminary outreach preparing communication materials to physicians who might you know one day see a case in a human either a traveler returning to New Mexico from an area where it's endemic or ultimately if it arrives here in New Mexico and could have risk of local transmission.
KC Counts:
Has there ever been a case in New Mexico?
Dr. Erin Phipps:
Not in the past several decades.
KC Counts:
Okay, good to know. I hope it stays that way. It sounds nasty.
Dr. Erin Phipps:
It was present in New Mexico up until the 60s. And there was a very interesting way that it was eliminated from the United States. They used what's called the sterile insect technique. And this was brilliant. So, they took advantage of the fact that the female fly only breeds once in her life. So, they have facilities that breed large amounts of screwworm flies, and they irradiate them so they're sterile. Those sterile males then mate with the females who lay eggs that do not hatch. And so, this was implemented back in the 50s and 60s, and the screwworm was progressively pushed south. It was eliminated from the U.S. in the 60s, and then it was continued. This effort was continued all the way down to Panama, so over the subsequent decades, it was eliminated first in Mexico, and then pushed further, and further south. And there was a barrier maintained in Panama with these sterile insects that for several decades kept Central and North America free from the flies.
KC Counts:
If I'm not mistaken, in recent years, there has been some research here at NMSU to create sterile mosquitoes. and send them out into the population. So interesting - sounds like it may be time to get back on that project.
Dr. Erin Phipps:
Yep, definitely.
KC Counts:
All right. Dr. Erin Phipps, thank you so much for sharing this important information with our listeners. We appreciate it.
Dr. Erin Phipps:
Thank you.
Screwworm infection is treatable. The CDC has more information right here.
