Vet Watch Update: New World screwworm

Transcript

Christopher Lee, DVM, MPH, DACVPM: This is a VetWatch update at DVM360. I’m Christopher Lee.

Cochliomyia hominivorax, the New World screwworm. I get asked whether or not there is a realistic potential for this fly to be hitting the US in the next year or so. Well, let’s take a look at the math to help answer that question. In addition, we can take a look at some of the math on white-tailed deer to help explain the overall devastation that this fly can impart.

If we take a look at the white-tailed deer population in the 1940s and ’50s, and compare it to the 1970s—after New World Screwworm was eradicated—we are looking at nearly a 10-fold difference in increase in population. Now, the eradication of screwworm was not the only factor that helped the deer rebound, but it was a major factor in this change.

Now, how did we eradicate Cochliomyia hominivorax from the US back in the ’60s? Well, to understand that, Cochliomyia hominivorax, the New World screwworm, has an Achilles heel—or Achilles tarsus, as it were. And that is that the female only has sex one time. Thus, if you can release irradiated, sterile males into the environment, when they have sex with the female, that female will no longer be able to produce viable eggs. And that is how it was done.

How many irradiated flies do you need in order to do this? Well, back in the 1960s, we had three laboratories producing 800 million flies per week—and that was out of the combined efforts of a laboratory in Panama, Mission, Texas, and Chiapa de Corzo (near Tuxtla Gutiérrez, Chiapas, Mexico). And through that, we had 800 million. Well, what is being done now? Right now, the only one that is currently still working is COPEG in Panama. They are at max capacity and they’re releasing up to 100 million pupae per week into the environment through ground boxes as well as air release.

And while we truly appreciate those efforts, that is not stopping the motion. We have been seeing New World screwworm moving up from South America, through every single country in Central America, and has touched down into Mexico. Currently, we are looking at the numbers nearly doubling every couple of weeks. It has gone from a couple of sightings of New World screwworm in Mexico, to dozens, to now over 400 different sightings of this fly in Mexico. Very scary. There are only two Mexican states separating confirmed New World screwworm cases from the U.S. border.

So what does this mean? Well, it means that invasion is likely. We are likely to see the New World screwworm here this year, if not next. It also means that there is the potential to create devastation—to our protein production, to our pets, to ourselves, and to the wildlife. Thus, we need to keep vigilant. If there’s any concern that you may be seeing this fly, there are many labs that will help identify maggots or adults.

Since our last New World Screwworm video, cases in Mexico have surged past 1,400. There is now only one Mexican state separating confirmed New World screwworm cases from the Texas border. And over the weekend, due to this, the U.S. halted all cattle imports from Mexico—a move that could impact anywhere from 1.2 to 1.8 million head of cattle annually. That’s a major hit to our beef supply chain. And this isn’t just a foreign animal disease threat—it’s actively knocking at our door.

So stay alert, know how to recognize it, and do not hesitate to report any potential cases. Thank you for tuning in to Vet Watch, only at DVM360, where what you know today protects everybody tomorrow.