While New World screwworm (NWS) is a foreign pest to the U.S., Dusty Oedekoven, National Pork Board’s chief veterinarian, says it was not unexpected.
“We’ve been watching the northward expansion of the fly for a couple of years,” Oedekoven says. “USDA has taken a proactive approach to preparing for that. There’s a lot of information available at screwworm.gov about the current status, as well as planned response activities.”
Oedekoven shares an update with U.S. pork producers on what to look for and how to protect their herd from NWS.
What makes NWS different than other threats we typically face?
One of the ways that it’s different is this is a parasite, a fly that lays its eggs in the wound, an open wound of any warm-blooded animal, so it’s not really a contagious disease like we would think of with African swine fever virus, for example. We have medications that can treat myiasis or really any parasitic disease. FDA has worked to approve products which can be effective against NWS, so it’s really not something to panic over. It is something to be aware of and the most important thing people can do right now is to be observant of their animals.
What is New World screwworm?
This parasite is a fly. In fact, it can look very similar to other flies that we’re used to seeing. It does have some distinguishing characteristics, but to the naked eye, it’s going to look like a fly. The thing you’re more likely to see is the effects of the female fly laying its eggs in an open wound. In the swine industry, we have a lot of potential there with bite wounds, fight wounds, castration and teeth clipping. Any sort of processing that can leave an open wound creates an opportunity for that fly to lay an egg in that wound. Later, the larvae eat the living tissue and that’s where the damage occurs – from that larval growth process before they drop off of the animal onto the ground and then develop into the next stage, the flying insect. The cycle then continues.
What signs should producers look for?
Being observant of potential signs is very important. Things to look for are head shaking, irritability, lethargy or animals that are off feed. Look for visible wounds that are not healing or are getting worse. You can see the larvae in wounds at some point. The other thing that’s distinctive about NWS infestation is that it has a very foul odor as the larvae eat into that tissue. I heard the state veterinarian in Texas say it best: “The best thing we can put on our animals right now is our eyeballs.”
What biosecurity tips do you recommend now?
As we think about biosecurity related to viral or bacterial infections, cleaning, disinfection and maintaining a sanitary environment remain important. This is especially true with NWS because you need to specifically target flies. Fly control ensures you are not creating environments favorable to fly habitation. Anything you can do to keep the flies down around your livestock is going to be an additive measure of biosecurity.
What are the most important thing producers need to hear?
First, be observant of all your animals – livestock and pets. Watch them every day. Be aware of the signs of NWS. Second, one of the ways we prevent movement of an infestation or parasite like this to a new area is through interstate health requirements. Whenever you’re moving livestock from state to state, it’s important to work with your local veterinarian to ensure you’re meeting state of destination requirements. The veterinarian’s going to look at the animals, ensure that they’re free of signs of contagious and infectious diseases or parasitism in this case, and also ensure that they are meeting the state of destination requirements, which in many cases, may change slightly with the incident that’s happening now in Texas.
