Hammerhead worms are once again making their way to backyards across the United States. They were most recently spotted in Washington, D.C and Virginia but have been around for some time. While they may look harmless, it’s important to note that they secret toxins that could be dangerous to humans and pets.

Theresa Dellinger, an entomologist with the Insect Identification Lab at Virginia Tech provides tips for what to do if you encounter one.  

What do hammerhead worms look like?

The head of these flatworms resembles that of a hammerhead shark, hence the name. They have a yellow-ish brown striped body and can grow well over a foot long.

Where are they found?

“They are native to Asia, but have been present in the United States for many years, with sightings throughout the eastern U.S and the Pacific Coast,” says Dellinger. “They probably entered the United States through the horticulture trade, in the soil of potted plants and spread throughout the country the same way.”  

“You will not find hammerhead works in hot, dry areas,” Dellinger explains. “Hammerhead worms prefer moist organic matter where their prey - earthworms and mollusks - can be found.” This includes: leaf litter, wet mulch, garden and flower beds.

Are hammerhead worms dangerous?

“Some, but not all species of Bipalium produce a neurotoxin, tetrodotoxin, in their mucus with the purpose of subduing their prey.” Dellinger explains that they cannot bite or inject this toxin into humans. “The likelihood of hammerhead worms harming people or animals is low and would require getting the mucus in the mouth or eyes.” If that does happen, Dellinger says the toxin may cause irritation to the skin or mucous membranes. Consult your medical provider if you suspect you are having a reaction after handling a hammerhead worm.

What should I do if my pet eats a hammerhead worm?

“Consult your veterinarian if your pet develops medical symptoms after licking or ingesting a hammerhead worm,” says Dellinger. “If possible, take a photo of the worm or place the worm in a container with a preservative like hand sanitizer to show the veterinarian.”

What should I do if I find a hammerhead worm?

  • Wear gloves when handling hammerhead worms to avoid exposure to their mucus.

  • Do not cut the worm up as it can regenerate from sections of its body.

  • Place the hammerhead worm in a container or bag that it cannot escape.

  • Kill the worm using one of the following methods, then dispose of the container in the trash:

    • Place the container in the direct sun for several hours.

    • Sprinkle some table salt in the container.

    • Squirt some hand sanitizer in the container.

    • Place the container in a freezer.

    • Put soapy water in the container.

  • Wash your hands thoroughly afterwards and avoid getting any mucus in your mouth or eyes.

Can I treat my property for hammerhead worms?

“It’s best to deal with individual hammerhead worms as they are found,” says Dellinger. “ Don’t spread salt or pesticides on the ground preventatively to kill hammerhead worms. It will harm vegetation and beneficial organisms.”

Do I need to report sightings of hammerhead worms?

There is no need to report hammerhead worms to Virginia Cooperative Extension.

About Dellinger

Theresa Dellinger is a diagnostician at the Insect Identification Lab in the Department of Entomology at Virginia Tech.  


To schedule an interview, contact Margaret Ashburn in the media relations office at mkashburn@vt.edu or 540-529-0814.

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