A Potentially Deadly Threat to Dogs Is Expanding Across the United States
A new study has found that a parasite known to be lethal to dogs that was previously found in Texas and some Gulf states has spread west to Southern California, suggesting that the threat is expanding across the country.
Researchers with the University of California, Riverside, found the parasite, Heterobilharzia americana, a flatworm also known as the liver fluke, in the Colorado River on the border of Arizona. The team traveled to Blythe, CA, a border town east of Joshua Tree National Park, after learning that several dogs had been infected after swimming there.
The parasites get into the veins of the intestinal lining where it develops into an adult and mates. However, the eggs are what triggers the infection when they get into the lungs, spleen, liver, and heart of the animal. When the immune system kicks in, hard clusters of cells called granulomas form, which eventually cause the organ tissues to stop functioning. In addition to dogs, mammals such as raccoons, marsh rabbits, horses, bobcats, mountain lions and opossums can be infected.
“Dogs can die from this infection, so we are hoping to raise public awareness that it’s there,” Adler Dillman, UCR nematology professor and co-author of the study, told UC Riverside News. “If you’re swimming in the Colorado River with them, your pets are in peril.
The parasite is transmitted by snails, so the research team collected more than 2,000 specimens from the banks of the river. They discovered two species of snails that were "actively shedding" the worm, which was also a surprise to the researchers who didn't even know the snails had migrated there in the first place.
It can take several months for symptoms to appear once a dog has been infected by the parasite. A total of 11 dogs in three counties in California have been diagnosed with the disease since 2019, and health officials hope to prevent further infections and deaths.
"Symptoms start gradually with a loss of appetite, and eventually include vomiting, diarrhea, profound weight loss, and signs of liver disease," explained Emily Beeler, a Los Angeles County Department of Public Health veterinarian. "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 added that treatment typically involves use of multiple medications and close monitoring of the dog by a veterinarian.
However, the good news is that humans can't contract the disease, and it's also not at risk of contaminating drinking water. The worms are relatively large, and can be easily filtered using common water purification strategies.
"You have viruses, bacteria, and other parasites such as Giardia in rivers," Dillman added. "Nobody should be drinking straight out of the river, and that has nothing to do with this particular parasite."
