Potentially fatal dog parasite found in part of Colorado River for first time, having spread from other states

A potentially lethal parasite that can infect dogs and other mammals has been found in the Colorado River in Southern California for the first time.

Potentially fatal dog parasite found in part of Colorado River for first time, having spread from other states

A parasite that can potentially kill dogs has been discovered for the first time in the Colorado River in Southern California, according to a study from the University of California, Riverside.

The parasite is called Heterobilharzia americana, which is a flatworm more commonly known as a liver fluke. 

It had previously mainly been found in Texas and other Gulf states but has now spread west.

"Dogs can die from this infection, so we are hoping to raise public awareness that it’s there," UC Riverside nematology professor Adler Dillman told the UC Riverside News. "If you’re swimming in the Colorado River with them, your pets are in peril."

Researchers with the school headed to Blythe, California, on the border with Arizona, and collected and tested 2,000 snails on the banks of the Colorado River there after finding out several dogs infected by the parasite had all swum there. 

The study said the findings suggest "a wider distribution [of the parasite] than previously reported. Our findings have implications for public health, veterinary medicine, and biodiversity conservation, contributing to developing effective control strategies to prevent the spread of this emerging infectious disease."

"In our study, we successfully confirmed the presence of Heterobilharzia americana for the first time along the shores of the Colorado River, infecting two species of snails, Galba humilis and Galba cubensis," the study authors said. "This significant finding marks the westernmost record of this endemic North American schistosome in the U.S. The identification of the parasite in an area with a documented history of canine schistosomiasis emphasizes the persistence and potential expansion of this parasitic threat."

Heterobilharzia americana is endemic to the Gulf Coast and South Atlantic region of North America, but it has also been found in states such as Indiana, Tennessee, Oklahoma, Arkansas and, most recently, Utah.

Along with dogs, it can infect mammals such as raccoons, marsh rabbits, horses, nutria, bobcats, mountain lions and opossums, the study said.

Once inside the skin, the parasite migrates into the lungs where it can cause hemorrhaging.

"It gets into the veins of the intestinal lining, and that’s where it develops into an adult and mates," Dillman told the UC Riverside News. "The presence of the adults in the veins isn’t the problem. It’s the eggs that get into the lungs, spleen, liver and heart. The immune system tries to deal with it, and hard clusters of immune cells called granulomas form. Eventually, the organ tissues stop functioning."

Eleven dogs in three counties have been confirmed to have the disease, and one has died, the UC Riverside News said, adding that symptoms, including "loss of appetite, and eventually include vomiting, diarrhea, profound weight loss, and signs of liver disease," can take months to show up.

"Treatment typically involves use of multiple medications and close monitoring of the dog by a veterinarian," Emily Beeler, a veterinarian with the Los Angeles County Department of Public Health, told the newspaper. 

The parasite can cause swimmer’s itch in humans but not an infection.