Dog-killing parasite found in California river. Here’s where and signs your pet might have it
A potentially fatal dog worm lurks in California’s waters, waiting to attack your dog from the inside.
A group of scientists from UC Riverside confirmed the presence of Heterobilharzia americana — a flatworm known as liver fluke — along the banks of the Colorado River in Southern California.
The parasite is likely more widespread than that region, according to professor Adler Dillman, chair of UC Riverside’s Department of Nematology.
The dog worm can cause canine schistosomiasis, an illness that attacks a dog’s liver and intestines, according to a March 14 news release. If left untreated, your dog’s organ tissues could stop functioning.
“If you do get into the water, there is a possibility that your dog could get infected,” Dillman told The Sacramento Bee Monday morning via phone.
In January 2023, veterinarian Emily Beeler with the Los Angeles County Department of Public Health contacted Dillman after documenting 11 cases of canine schistosomiasis over the past five years across Los Angeles, Orange and Riverside counties.
Several dogs were sickened, and one dog died from the disease.
“They suspected it was here but they needed someone to do the dirty work, to collect the snails and look for the parasite,” Dillman said. “I was all too eager to do that ... I love parasites.”
Dillman and a team of scientists collected more than 2,000 snails from the banks of the Colorado River at Hidden Beaches Resort in Blythe, a town east of Joshua Tree National Park in Riverside County, where the sick dogs swam.
Samples were collected between March 2023 and August 2023 using handled kitchen strainers and hands, according to a paper published on March 13 in the scientific journal Pathogens.
Dillman said it was a surprise to find the parasitic infection this far west because it’s almost exclusively found in Gulf Coast states including Texas, Florida, Alabama and Georgia.
What are the symptoms of canine schistosomiasis?
Dillman said the “tricky” part about canine schistosomiasis is it’s curable if caught in time. However, he said, the worst of the symptoms can take months to materialize in your dog.
“If you’re swimming in the Colorado River with them, your pets are in peril,” he said in the March 14 news release.
Here’s a list of symptoms to watch out for:
If you notice these symptoms, take your dog to the vet immediately.
“If your dog has these symptoms after swimming in the Colorado River, it’s a good precaution to ask your veterinarian for a simple fecal test,” Beeler said in the release.
A stool sample will be collected to check for the presence of parasite eggs. Once the infection is confirmed, your pet will be prescribed medication to clear it.
How does a dog get infected by a flatworm?
Dillman said the parasite needs snails, freshwater and a mammal to host it.
First, a mammal host sheds parasite eggs in its poop, according to the Los Angeles County Department of Public Health.
After the egg hatches in the water, a “free-swimming form of the parasite” penetrates a snail and develops into a flatworm.
The flatworm has about 24 hours once it ventures out of the snail to find another mammal host to penetrate directly through the skin and infect.
The parasite reproduces inside the host and its eggs travel to the animal’s lungs, spleen, liver and heart.
Dillman said raccoons are most susceptible to the parasite. Bobcats, mountain lions, horses and dogs are also in danger.
Dogs and raccoons can be exposed when they are in the water or drinking it.
Are humans in danger?
Not really.
“These (flatworms) can penetrate through the skin of a person, but that’s where the story ends,” Dillman said, adding that a human’s immune system is equipped to stop an infection.
The parasite could cause a rash but that would be the extent of your symptoms.
What’s being done to combat parasites?
Dillman said the scientists’ next step is to collect additional samples to gauge how widespread the flatworm infestation is.
However, he said, the parasites are not being irradiated from the water at this time.
The Bee reached out to Beeler for comment, but she was not available for an interview as of Monday morning.
This story was originally published March 18, 2024 at 2:11 PM with the headline "Dog-killing parasite found in California river. Here’s where and signs your pet might have it."