UC Riverside researchers have verified, for the inaugural time, the presence of a potentially lethal parasite in dogs within a segment of the Colorado River flowing through California in March.
The parasite, known as Heterobilharzia americana or liver fluke, is a flatworm that has traditionally been concentrated in Texas and other states along the Gulf Coast. However, its occurrence in this region of the Colorado River in California marks a significant deviation from its usual range. This worm poses a threat to dogs, causing canine schistosomiasis, a condition affecting their liver and intestines.
Adler Dillman, a nematology professor at UCR, emphasized the potential severity of the infection: “Dogs can die from this infection, so we are hoping to raise public awareness that it’s there. If you’re swimming in the Colorado River with them, your pets are in peril.”
Prompted by reports of infected dogs in the area, Dillman mobilized a research team to investigate. They focused their efforts in Blythe, a town bordering Joshua Tree National Park in Riverside County, where the affected dogs had all been exposed to the river.
The transmission of the infection relies on a snail species that serves as an intermediary host for the worm. The researchers gathered over 2,000 snails from the riverbanks. Their findings, published in the journal Pathogens, detail how DNA analysis confirmed the identity of both the snails and the flatworm.
“We actually found two species of snails that can support H. americana in the river in Blythe, and we found both snails actively shedding this worm,” Dillman explained. “Not only was it a surprise to find H. americana, we also did not know that the snails were present here.”
After undergoing transformation within a snail host, the worm emerges with the aim of infecting a mammal. During this phase, it can only survive independently for approximately 24 hours. If a dog or raccoon comes into contact with the contaminated water or ingests it, they become susceptible to infection.
“It gets into the veins of the intestinal lining, and that’s where it develops into an adult and mates,” Dillman explained. “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.”
Following infection, it may take several months before the most severe symptoms manifest. Since 2019, 11 dogs across three California counties have been diagnosed with this disease, resulting in one fatality. Health authorities aim to prevent further infections and deaths through increased awareness.
“Symptoms start gradually with a loss of appetite, and eventually include vomiting, diarrhea, profound weight loss, and signs of liver disease. 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,” advised Emily Beeler, a veterinarian with the Los Angeles County Department of Public Health.
“Treatment typically involves use of multiple medications and close monitoring of the dog by a veterinarian,” added Beeler.
Relevant articles:
– Dog-killing flatworm discovered in Southern California, University of California, Riverside
– Are Flatworms Harmful to Humans? Get the Answer at BYJU’S NEET, byjus.com
– Presence of parasite that’s deadly for dogs now confirmed in California: Signs to watch for, Los Angeles Times, Mar 14, 2024
– California Dog Owners Warned of Lethal River Parasite, Newsweek, Mar 15, 2024