Dog-Killing Parasite Worm Detected in California For the First Time

A new study has reported that a worm parasite that can infect and kill dogs has been picked up in California for the first time. It was specifically detected in the Colorado River banks close to the border of Arizona.

Dog-Killing Parasite Worm

The parasite, known as Heterobilharzia americana, has been mainly found in the Gulf Coast as well as South Atlantic states. However, in recent years, its range appears to have expanded to other regions.

In canines, this worm can lead to a potentially deadly condition known as canine schistosomiasis. Nevertheless, the infection can be treated successfully with deworming drugs if it is promptly diagnosed. The parasite also cannot lead to the condition in humans, though it could lead to skin irritation and cause "swimmer's itch."

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First Detection in California

The researchers started checking the Colorado River after Dr. Emily Beeler, a veterinarian in LA County, reached out to them regarding a cluster of localized dog illnesses.

From 2018 to 2023, there were 11 dogs from counties in Southern California that got infected with canine schistosomiasis. One ended up dying due to the infection. All of them went swimming in the river before they fell ill. Their travel histories all suggest that the river could be a common infection source, even though the parasite was never reported in Southern California in the past.

Alder Dillman, the study's senior author, parasitology professor, and chair of the department of nematology in the University of California, Riverside, explains that the veterinarians were worried that something local could be present.

Hence, the team made several trips to Blythe, which is a border town roughly an hour east of Joshua Tree National Park. The researchers searched for tiny freshwater snails that serve as the parasitic host.

The worm parasites typically infect such snails shortly after they hatch, are slightly mature, and get released into the water that surrounds them. They then bear through a mammal host's skin and swim through the animal's bloodstream as they keep on maturing. They eventually reach a major intestinal vein, where they reproduce to lay eggs that are typically shed in the poop of animals.

However, there are times when the eggs end up moving through the bloodstream and lodging in crucial organs, such as the heart and lungs. They could end up producing hard lumps known as granulomas that the animal's immune system attacks. If such a condition is not treated, organ dysfunction or death could result.

The researchers gathered a total of roughly 2,000 snails. DNA analysis revealed that a huge percentage were from two species that are known as worm hosts. These are Galba cubensis and Galba humilis.

The scientists found that some snails also had the parasitic worm DNA. However, since only four out of hundreds were found to test positive, estimations regarding the number of infected snails are tricky to make. Though more snails in their samples could have been infected, it is possible that the worms may not have been mature enough for the analysis to pick up.

Nevertheless, what the study confirms is that snails from this area can get infected. Findings were noted in the "Canine Schistosomiasis in the West Coast: Heterobilharzia americana in Two Natural Intermediate Hosts Found in the Colorado River, California" study.

With this, the study authors want California residents to know about the risks of canine schistosomiasis and the early symptoms of the condition. Such early symptoms include appetite loss, weight loss, lethargy, bloody diarrhea, and vomiting.