Is Your Dog at Risk? New Lethal Parasite Found in Popular Swimming Areas

Kazantseva Olga /
Kazantseva Olga /

A potentially lethal parasite has been identified in California’s Colorado River for the first time, as per a recent study conducted by researchers from the University of California.

The parasite, Heterobilharzia americana, belongs to the liver fluke category of flatworms. Previously confined to the Gulf states, this parasite has now extended its reach to the United States’s western region, as researchers from the University of California at Riverside reported.

Nematology professor Adler Dillman from UC Riverside emphasized the gravity of the situation, stating, “Dogs can die from this infection, so we hope to raise public awareness that it’s there. If you’re swimming in the Colorado River with them, your pets are in peril.”

The infection caused by this parasite, termed canine schistosomiasis, primarily affects dogs’ livers and intestines. Transmission of the parasite mainly occurs through a snail intermediary.

According to researchers, since 2019, 11 dogs in three California counties have been diagnosed with the infection, resulting in one fatality.

After the revelation that all infected dogs had swum in the Colorado River in Blythe, California, researchers collected approximately 2,000 snails. Their investigations revealed that two species of river snail harbor the parasite.

Mr. Dillman noted, “We found two species of snails that can support H. Americana in the river in Blythe, and we found both snails actively shedding this worm. It was a surprise to find H. americana, but we did not know that the snails were present here.”

The study suggests a broader distribution of the flatworm than previously understood. While previous studies have primarily documented infections in Texas and Louisiana, occurrences have also been reported in other states.

The researchers underscored the significance of their findings, stating, “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.”

The parasite poses a substantial risk to animals, including dogs, as it resides in the blood vessels and can cause liver inflammation during mating. Exposure typically occurs when animals wade or swim in freshwater, allowing the immature stage of the parasite to penetrate the skin and migrate to the intestines.

Symptoms of infection in dogs may include weight loss, hematochezia, melena, diarrhea, vomiting, and lethargy. Veterinarians recommend a fecal test for dogs displaying these symptoms after swimming in the Colorado River.

In response to the emerging threat, the Los Angeles County Department of Public Health issued a warning last year, urging veterinarians to be vigilant regarding symptoms of parasitic dog infections reported in Orange, Los Angeles, and Riverside counties.