Hammerhead flatworms — an invasive pest that looks like a cross between a hammerhead shark and a leech — have been spotted in the Washington, D.C., area and across the United States.

Experts say the worms secrete toxins that can be somewhat dangerous to humans and pets, and they’re bad for the ecosystem. Here’s what you need to know about the worms, including the right way to kill them.

“It might kind of look like a leech to you, but it won’t have the segments along it. So it’s a flatworm that has a hammerhead shape.

So, if you think of the hammerhead shark and a worm combined, that’s exactly what this flatworm looks like. And it is a predator of earthworms and an invasive species,” Ashley Morgan-Olvera, the director of research and education at the Texas Invasive Species Institute said.

“Several hammerhead species are here and they’re pretty much across the United States,” Morgan-Olvera said. “They are found as far north as New York, over to California, throughout Texas and the southeastern United States.”

“They do use a neurotoxin, which can sound really scary, but it’s a neurotoxin that they use to digest the earthworms, and if mammals, such as ourselves or cats or dogs were to accidentally ingest the flatworm, it can cause some nausea,” Morgan-Olvera said.

“It could possibly make your hands tingle if you touch it. I haven’t known very many people to have a reaction to it, but we do discourage anyone handling it.” She said it’s important to keep pets and children away from the worms if you spot them because they could cause nausea and vomiting.