UC Davis raises awareness on salmon poisoning disease

Ollie, a 7-year-old chocolate Labrador retriever, and his owners Sarah Christie and Dan York from Sacramento, California, enjoy traveling to their second home in Del Notre County in northwest California. However, Ollie’s recent health scare shed a light on a disease that Christie and York did not know was a possibility, raising their awareness for Ollie’s outdoor activities.

Christie shared that recently Ollie begged to go outside for an urgent bathroom break, but as the day went on she noticed that he was lethargic and trembling. Worried about him, they rushed him to an emergency veterinary clinic where his tests were inconclusive. The team gave Ollie antibiotics and advised his owners to look out for vomiting because his intestines were full, but not necessarily blocked. Christie shared that the following day, Ollie was not eager on his walk and was appearing to still be ‘under the weather.’

Two days later, Ollie was not eating and vomited, so his owners brought him back to the veterinarian, where it was confirmed that he was not blocked and provided him with anti-nausea medication. However, Ollie’s health continued to decline, and he was not responding to medication, so Christie made the choice to bring him to the UC Davis veterinary hospital. There, he was evaluated and stabilized by the Emergency and Critical Care Service before being transferred to the Small Animal Internal Medicine Service.

The team at UC Davis collected background information about Ollie, including his outdoor habits with his owner York, prompting them to ask if he had gone swimming in any rivers or encountered any raw salmon, giving them an idea of what could be going on with Ollie.

“Ollie presented with classic clinical signs of salmon poisoning disease – low platelet count, enlarged lymph nodes, and changes to his spleen,” said Emily Hirsch, DVM, a second-year resident and co-chief house officer of the hospital, in an organizational release.1 “Knowing that his owner is an outdoorsman and Ollie might be around salmon in those situations, I was almost certain that was the case.”

Christie explained to the UC Davis team that on a recent trip to Del Norte County, Ollie was on a walk near the Smith River, which is one of the best salmon rivers on the west coast, here, she said Ollie encountered some dead salmon. Christie said that although he did not take a bite out of any dead salmon, it was clear that he must have licked one and had enough of an encounter to be poisoned by the salmon’s parasitic flukes that contain Neorickettsia helminthoeca.1

“Typically, we have to take samples from the abdominal lymph nodes,” Hirsch explained. “But in Ollie’s case, we were able to get samples from his enlarged peripheral lymph nodes, meaning he was heavily burdened by this infection by the time we saw him, which is why he presented so sick.”

Salmon contracts flukes by eating snails, but not every salmon has flukes and not all flukes contain the bacteria. However, Hirsch warns that raw salmon without flukes could still be dangerous if ingested and cause other diseases, such as mercury poisoning.

For pets with salmon poisoning, they typically begin to show symptoms within a week and signs include lack of appetite, vomiting, diarrhea (which could possibly contain blood), enlarged lymph nodes, fever, weakness, discharge from the eyes or nose, weight loss, muscle tremors, seizures, increased respiratory rate, and increased heart rate. If the infection is not treated within 2 weeks, most dogs will not survive.2

If caught in time, like it was in Ollie’s case, salmon poisoning disease is easily treatable with the proper medication. Ollie was prescribed doxycycline to clear the infection and praziquantel to clear the flukes from his system. Within a few days of taking his medication, Ollie recovered, and his owners reported that he is back to normal and still enjoying outdoor activities, but York and Christie have a closer eye on him now.1

References

1. Dog’s Close Call with Salmon Poisoning Disease Shocks Owners but Raises Awareness. News release. UC Davis College of Veterinary Medicine. March 25, 2025. Accessed March 27, 2025. https://www.vetmed.ucdavis.edu/news/dogs-close-call-salmon-poisoning-disease-shocks-owners-raises-awareness
2. Schmid R. Salmon Poisoning. VCA Animal Hospitals. Accessed March 27, 2025. https://vcahospitals.com/know-your-pet/salmon-poisoning