Should I be worried about the deadly-for-dogs parasite found in California? A vet answers

Dog standing in the Colorado River in California
(Image credit: Getty Images/Alisha Bube)

A parasite, which can be deadly for dogs, has been found in the Colorado River in California.

If you're a pup parent who lives in the area, then you might feel a little worried if your little one recently paid a visit here.  That's why we've asked a vet to answer all of your questions - like whether it's something to be concerned about and how to prevent infection.

We recommend investing in the best pet insurance for scary situations such as this. With a sick pup, the last thing you want to worry about is a vet bill.

Some of the symptoms of Heterobilharzia Americana include a dog losing weight and vomiting. The disease is transmitted by the host (snails), and can be dangerous to dogs, horses and other mammals. Animals can become infected if they swim or wade in freshwaters that are exposed to it.

Here's a list of the other symptoms, according to the study published in the Journal of Pathagons.

  • Dermatitis 
  • Vomiting
  • Coughing
  • Fever
  • Bloody diarrhea
  • Anorexia
  • Weight loss
  • Lethargy
  • Excessive urination
  • Excessive thirst

The report concluded: "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. This significant finding marks the westernmost record of this endemic North American schistosome in the United States."

If you want to learn more about this parasite, we asked expert vet Dr. Lily Richards what you need to know:

Lily Richards
Dr. Lily Richards

Dr. Lily Richards is a vet with 11 years of experience in farm, equine, small animal and exotic patient care. After running a busy clinic she took a step into client education focusing on getting the right information to those that need it and are searching for help and advice from professionals online.

Do dog owners need to worry about this discovery?

Dr. Richard explains: "Dog owners should be aware of this emerging parasite as it has been found to have spread to the Colorado River on the border of Arizona in Blythe, just east of the Joshua Tree National Park. This finding suggests the parasite, which is thought to be endemic in Texas and some Gulf states, is spreading across the country. 

"Transmission is via an intermediate host (a snail), found near water courses, which incubates and grows the parasite to then be consumed by the end host (your pet dog) whilst swimming in infected waters. When your dog is infected, the parasite accesses the blood system via the gut and travels to organs such as the lungs, liver, spleen and heart causing damage via immune activation and granuloma formation resulting in organ damage and failure."

If owners think their dog has the disease, what should they do?

Dr. Richards says: "If you are concerned about your dog being unwell, up to several months after swimming in an affected area such as the Colorado River, you should contact your vet. 

"Your vet will likely perform an examination, and discuss any symptoms (usually loss of appetite, vomiting, diarrhea, weight loss, and signs of liver disease). A faecal test will be performed to look for the parasite and imaging may be required to check for internal damage of migrating parasite life stages. 

"Treatment is with two different types of antiparasitic medication namely praziquantel and fenbendazole for a period of 10 days. Not seeking treatment can have life-threatening consequences. "

What preventative measures can dog owners take?

Dr. Richards says that the best preventative measure is to avoid direct contact with water in which the parasites are known to be present in.

For more dog advice, take a look at our other features on 32 common dog diseases to keep an eye out for and is my dog sick?

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Megan Milstead
Staff Writer

Megan is a Staff Writer on PetsRader, covering news, features and buying guides. She has a wealth of experience looking after animals, having grown up with dogs, cats and horses all of her life. She’s particularly interested in pet happiness and behavior, which she loves to research in her spare time. You’ll often find her watching webinars on reactivity in dogs or researching cat body language. She loves going the extra mile for her cats Chilli and Nala (who also help out with testing the best products for our buying guides). 


Megan studied BA Journalism at the University of Westminster, where she specialized in lifestyle journalism and was editor of Smoke Radio’s online magazine. She also graduated from West Herts College with a Level 3 Extended Diploma in Journalism. Before joining the PetsRadar family last year, she worked on the editorial team at Harrods and has spent most of her career writing for specialized titles, like RunningShoesGuru, Licklist and Mr. After Party. 


Megan works alongside qualified vets and accredited trainers to ensure you get the best advice possible. She is passionate about finding accurate and helpful answers to your pet-related questions.