The Danger of Feeding Dogs Raw Trout

Kero in her "room" at the veterinary hospital with her  IV tube and cone removed during one of my visits (she's hiding her arm under her body in the hopes that we wont reconnect the IV tube.)

[Note: Click here to skip the story and jump to the important part.]

A few weeks ago my lovely husky, Kero, fell very sick. Initially, she seemed confused, was walking strangely, and would hardly eat anything. Kero had been on a walk with the dog walkers earlier in the week on a very hot day. I wondered if perhaps she had become dehydrated. It also occurred to me that she might have re-injured her back (broken years ago in a car accident.) Perhaps something had happened while running or playing that had caused a swelling in a disk, impacting her spinal cord.

I didn’t want to over-react, but I kept a close eye on her. At one point when she was laying down I threw a treat to her. It bounced past her. She lifted her head, looked at the treat, and then put her head back down again. This was not good. I went over and examined her. She allowed me to touch, poke, and prod her everywhere, including her feet. She never lets anyone touch her feet without a major hassle. I was very worried. It was time to go do the vet.

It was a Saturday, so our usual veterinarian wasn't there, but the vet who saw Kero was very careful and concerned. I mentioned the heat on the walk, her back, and the fact that I had fed her some raw mackerel a week earlier. After the examination the veterinarian opined that there were a couple different possibilities, but she suspected pancreatitis. Blood was drawn for a full set of tests and Kero’s back and belly were x-rayed. We were sent home to await the results, along with some pain medication in case it was a physical injury that was causing Kero distress.

The next day I got the call with the results: the x-rays showed that Kero’s back was unchanged; she still had the old damage from her earlier injury, but nothing new had happened to explain her behavior. The x-rays didn’t show anything else going on in the areas that were filmed. Her blood tests however showed significant pancreatic enzymes in her blood – clear evidence that her pancreas was damaged, presumably by pancreatitis. However, pancreatitis is normally accompanied by vomiting and diarrhea. Kero wasn’t showing those symptoms.

The following day I brought her back in for more tests and a day of IV fluids. Then again the next day, and the next. One by one they ruled out every possibility except pancreatitis through x-rays, ultrasound, and blood and urine tests. Still, there was no vomiting. They began keeping her overnight, feeding her orally with a syringe. She refused to eat on her own.

Eventually she began having diarrhea. Major, explosive, projectile diarrhea. But no vomiting. At that point I asked my vet if it was possible that she had a parasite such as giardia as well as pancreatitis. We were expecting diarrhea with the pancreatitis, but there should have been vomiting too, and timing of the diarrhea was odd. A stool sample was sent off for analysis. The result: Salmon Poisoning Disease (SPD).

I was confused. I had recently fed her raw mackerel, but definitely not salmon. I knew that raw salmon was a no-no. A couple years earlier a neighbor’s dog was dying of cancer. I commiserated with her about her dog’s condition. She wondered what would be on his “bucket list.” I said I knew what would be at the top of Kero’s list: a whole fresh salmon. After that conversation it occurred to me, why wait until your dog is dying to give them the thing you think they would like most in this world. On the other hand, I was worried about fish bones and so forth, so I went online to see if there was anything I should know before giving her such an über-treat.

I found a lot of web sites, blogs, and discussion groups that talked about feeding your dog raw food – fish or otherwise. There were many people that praised raw food as the ultimate source of canine nutrition; after all, dogs evolved from wolves. There were just as many who felt that raw food was dangerous – dogs aren’t wolves just as we aren’t chimps, and the raw ingredients we buy in grocery stores may contain all kinds of contagion that would normally be destroyed by cooking. Regardless of which side a web site or author came down on regarding raw food they all agreed on one thing: no raw salmon. In the end I decided that I would feed her some raw fish from time to time – as long as it wasn’t salmon. Kero was wildly enthusiastic about the new addition to her diet. Hence the mackerel I had fed her the week before.

Now the test results were showing positive for salmon-flukes. But I hadn’t fed her any salmon. I went online to see if there was anything wrong with feeding a dog raw mackerel. Try as I might, I couldn't find a single mention of mackerel being a problem. I wasn’t certain exactly when I had bought the fish, or where. I suspected the mackerel might be an important clue, so I went through my credit card slips to nail down the details. What I found was a surprise. I had totally forgotten - a few days earlier I had purchased a trout at a local grocery store for my dinner that night. I have no idea why I remembered the mackerel the prior week, but forgot the more recent trout.

I was sure the trout had come eviscerated – they always are. As I thought back I recalled coating it with egg wash and flour and pan frying it. But I couldn’t for the life of me remember if I had cooked it head on, or if I had removed the head and given it to Kero. Regardless, I returned to the internet to search for information on salmon flukes and trout.

Here is what the Merck Vet Manual has to say:

[Salmon Poisoning Disease] is caused by Neorickettsia helminthoeca and is sometimes complicated by a second agent, N elokominica , which causes EFF [Elokomin fluke fever]. The vector of both agents is a small fluke, Nanophyetus salmincola . Dogs and other animals become infected by ingesting trout, salmon, or Pacific giant salamanders that contain encysted metacercariae of the rickettsia-infected fluke. In the dog’s intestine, the larval flukes excyst, embed in the duodenal mucosa, and introduce the rickettsiae. The fluke infection itself produces little or no clinical disease.

Yup, raw trout can contain the same fluke that causes Salmon Poisoning Disease. The big problem is that the disease is known as “Salmon Poisoning Disease,” but it can be caused by ingesting any raw salmonid species. The members of the family salmonidae include salmon, trout, char, freshwater whitefish, and graylings. Though I couldn’t be certain, I must have removed the head from the trout and given it to Kero, not realizing that trout can carry SPD.

As soon as the diagnosis was made they began administering anti-parasitic drugs for the fluke and antibiotics for the associated bacteria (which is the actual agent of the disease.) Within a couple of days Kero’s fever was down, the diarrhea had stopped, and she had begun eating on her own. She came home. In just a few days she was back to her old self (though almost 25% lighter.) A few weeks later only the missing hair where she had been shaved remained as a reminder of her ordeal. A follow-up urine test showed no indication of pancreatitis.

I was surprised at how many web sites make reference to the danger of feeding dogs raw salmon, but few mention trout. Even my vet had not known that raw trout could carry the fluke that causes SPD. It is worth noting that untreated, SPD is fatal in 90% of cases. So, I hope that this blog posting might help to spread the word, and maybe, just maybe, save other dogs (and their faithful guardians) from considerable pain.