Presence of parasite that's deadly for dogs now confirmed in California: Signs to watch for

In January 2023, Dillman said Beeler called and asked him to test those waters for the parasite.

Dog owners told him they had visited two primary places, Quechan Park and Hidden Beaches Resort.

Dillman and his team's first discovery was that the two species of snails that carry the parasite had migrated to California.

How they arrived remains a mystery.

"We don't know how these snails reached California," Dillman said. "It's a bit complex."

The professor noted that there was an outbreak of canine schistosomiasis in Moab, Utah, in 2018. Ultimately, 12 dogs living near a man-made pond with those snails present tested positive. Dillman said the location of that pond was only a couple of miles from the Colorado River.

"Researchers didn't check to see if the snails were in the river," he said. "It's possible they're there."

Along with dogs, the parasite has been known to infect raccoons and horses.

The disease cannot be transmitted between dogs and humans, though people may develop a self-limiting rash (meaning it goes away on its own without treatment) after swimming or contacting contaminated waters, according to Sara Strongin, chief veterinarian at the Riverside County Department of Animal Services.

The snail excretes a juvenile form of the worm, which then has 24 hours to find a mammal host to infect or die, according to Dillman.

The goal of the worm is to reach the intestines of a host, where it continues to develop into an adult. There it mates and releases thousands of eggs, Dillman said. Those eggs clog the lungs, spleen, liver and hearts of hosts along with immune cells called granulomas that fight them.

Eventually, organ tissue stops functioning, Dillman said.

If found in time, however, antiparasitics like praziquantel and fenbendazole can help fight off an infection.

"The goal here," Dillman said, "is to get awareness out and make sure dog owners know what signs to look for."