ZION NATIONAL PARK (ABC4 Utah) — The Narrows, one of the most popular hikes in Zion National Park that requires visitors to walk in the Virgin River, will remain open amid a public health warning due to a toxic algae bloom found in the river’s north fork, park officials told ABC4 News on Monday.

A 5-month-old husky puppy died July 4 an hour after swimming in the river along the Pa’rus Trail, exhibiting symptoms of possible exposure to cyanobacteria toxins, those produced by harmful algal blooms, according to park rangers. The dog could not walk, was in pain, and was having seizures.

“The dog was snapping it and potentially ate some of the algae,” Zion’s chief of resources and research Cassity Bromley said. “That’s what triggered us to start testing and looking for this in the water.”

Bromley said it’s the first time anatoxin-a, a neurotoxic cyanobacterial toxin, has been detected in the area. She tells ABC4 News the toxin has a very short half-life, meaning it doesn’t stay very long in the environment. Testing so far has been limited within the park, but environmental scientists are expanding the monitoring and testing as the bloom affects the water downstream.

“The primary thing right now is to keep from drinking the water or getting it in your nose or mouth,” Bromley said.

Since dogs have smaller livers than humans, Dr. Kate Fickas with the Utah Department of Environment Quality (DEQ) said they’re much more susceptible. Dogs may experience convulsions, seizures, respiratory issues, and/or foaming at the mouth, along with gastrointestinal distress and lethargy. Symptoms can appear within minutes, and, unfortunately, there’s no cure for algae poisoning, officials say.

Officials with the National Park Service said on Friday night they received results from water samples taken in the river, with some samples showing an anatoxin-a concentration greater than 55 micrograms per liter. The health threshold for primary recreation from the Utah Department of Health and DWQ is 15 micrograms per liter. 

“[A harmful algal bloom] could look like pea sour or appear in a bright cyan green color. Sometimes, you may not even see surface scum. Another type might look like grass clippings, like someone spilled their lawn mower bag straight into the body of water. Other signs can be spilled paint and sometimes we see it in clumps,” said Dr. Fickas.

Zion National Park has posted signs to warn visitors not to swim or submerge themselves and to keep pets out of the water. Residents and visitors should adhere to the following guidelines:

  • Do not swim in this area.
  • Avoid areas of algae scum.
  • Keep animals away.
  • Do not drink the river water (including water passed through a filter or purifier).
  • Clean fish well and discard guts.

This warning does not apply to Quail Creek Reservoir, Sand Hollow Reservoir, or the Santa Clara River basin, officials stated.

Katie Karalis
Katie worked as a multimedia journalist in Reno, Nevada for KRNV News 4 and in Quincy, Illinois for WGEM-TV before making the move to Utah. Katie graduated from Northwestern University’s Medill School of Journalism where she anchored and reported for the Emmy-award-winning Northwestern News Network.