Hammerhead worms, an invasive and toxic species originating from Southeast Asia, are present in several Ontario communities this spring, including cities in the GTA and surrounding areas, according to recent reports.
Experts believe they came to North America in shipping containers.
The worms, also called shovelhead worms, secrete a dangerous neurotoxin called tetrodotoxin, which is also found in pufferfish. It can cause skin and eye irritation in humans and can harm a pet if ingested.
“While there are no documented cases of humans becoming ill from handling these worms, they should be avoided and if accidentally handled, wash hands immediately,” Conservation Hamilton says on its website.
Identifying hammerhead worms
Hammerhead worms grow to about 10 cm in length and can be multicoloured. They have no natural predators in Ontario.
The name is a general term for several flatworm species under the Bipalium genus.’
In addition to carrying a toxin, hammerhead worms have a parlour trick: If cut in half, they can spread into multiple new worms.
How do hammerhead worms spread?
Hammerhead worms won’t get too far on their own—they’re mostly moved by human activities.
Like most worms, they’re found in dirt and soil. You can help stop their potential spread by keeping soil local—don’t transport it to other communities. And if you need to dump soil, don’t dispose of it in wooded areas.
If you live in Ontario and spot a hammerhead worm, contact the provincial invasive species hotline at 1-800-563-7711, or visit the Invasive Species in Ontario project to log a report.
Header image: James Lees/Dundas Valley Conservation Area.
