Think Out Loud

Disease outbreak leaves sea lions stranded on Oregon Coast

By Rolando Hernandez (OPB)
Nov. 4, 2022 4:24 p.m. Updated: Nov. 14, 2022 6:23 p.m.

Broadcast: Friday, Nov. 4

As the number of sea lions in the Columbia River grows, so do debates over the best way to manage them.

A file photo of a sea lion. An outbreak of Leptospirosis this summer has led to over 150 sick or dead sea lions stranded on Oregon's coast. Symptoms of an infected sea lion include extreme lethargy, dehydration and the mammals reluctance to use their hind flippers to name a few.

Theresa Tillson, Oregon Department of Fish and Wildlife


More than 150 sea lions have been found sick or dead along Oregon’s coast due to a bacterial outbreak of Leptospirosis this summer. The disease is spread through the mammals’ urine and can be spread to other species such as dogs. Jim Rice is the stranding program manager for Oregon State University’s Marine Mammal Institute. He joins us to share what the outbreak has looked like so far and how it compares to previous years.

Note: This transcript was computer generated and edited by a volunteer.

Dave Miller: From the Gert Boyle Studio at OPB, this is Think Out Loud. I’m Dave Miller. More than 150 sea lions were found sick or dead along Oregon’s coast this summer because of a bacterial outbreak called Leptospirosis. The disease can affect other mammals as well, including dogs. Jim Rice is the person who gets called when a sick or a dead sea lion ends up on the shore. He is the stranding program manager for the Oregon State University’s Marine Mammal Institute. He joins us now to talk about this outbreak and more. Jim Rice, welcome to Think Out Loud.

Jim Rice: Thanks Dave. I’m happy to be here.

Miller: What exactly is Leptospirosis, if I’m pronouncing that correctly?

Rice: Well, it’s a bacterial infection that largely affects the kidneys of California sea lions. It makes them unable to process their urine properly. They become dehydrated. And it can lead to a cascading of other health problems that often accompany Leptospirosis, primarily pneumonia, which can actually be what kills a lot of these animals that are compromised because of the kidney disease that they get.

Miller: What are the symptoms of the infection? If you come upon – after someone has alerted you – a sea lion on the shore, dead or in trouble, what do you see that would let you know: Oh, it probably is this disease?

Rice: That’s a good question. Sea lions can succumb to lots of different ailments. With Leptospirosis, they typically become very lethargic. So they’re very weak, unable to move their bodies properly. They’re often unwilling or unable to move their hind flippers. They generally don’t move very well when they’re out of the water. They’re often very thin, too. They tend to lose weight pretty consistently when they’re sick with Leptospirosis. Sick animals generally don’t eat well. As a result they lose a great deal of weight. They become dehydrated and just basically extremely lethargic and allowing people and dogs to approach them, which is not something a normal, healthy sea lion would tolerate.

Miller: What would they do normally?

Rice: Yeah, they would usually go back into the water or perhaps just try to move away. But generally when these animals are very sick, they will just lie there and allow things to come up around.

Miller: How deadly is Leptospirosis?

Rice: Well, it seems to be pretty deadly to the sea lions that show up sick with it. But I would also point out that a lot of sea lions within the population – and there is a single population of California sea lions that live along the west coast of North America basically that we have here in Oregon, Washington and California. These animals, a fair number of them, have what we call positive titers for Leptospirosis, or Leptospira, the organism that causes the disease. These are animals that have been exposed to this disease previously in their lives and have successfully defended themselves against it. So we know that there are a fair number of these animals that can survive Leptospirosis. But, the animals that are succumbing to it are more vulnerable than those animals, and for some reason they are becoming acutely ill. This happens in discrete outbreaks that happen every several years along the West Coast.

Miller: So it seems like it actually may be hard to really pinpoint the percentage of sea lions who get this bacteria who die from it. But, [of] the ones that are washing up on shore, or ending up on shore stranded somehow or dead, a high percentage of those have this disease.

Rice: Yes, I would agree with that. I don’t know the details of how many within the population would have it, and I’m not an epidemiologist, so it’s sort of outside of my expertise to make any kind of statements like that. But what you just said is certainly true. The animals that are coming ashore that are sick, it appears that the vast majority of those do seem to be sick with Leptospirosis. They are sharing those same classic signs. We have done complete necropsies on seven animals so far and have conclusive evidence that those animals did succumb to Leptospirosis and health effects that are related to it.

Miller: Maybe this is a question for an epidemiologist, which, as you just said, you’re not one. But do you have a sense for how this disease is spread?

Rice: It’s generally believed that it’s spread through body fluids and primarily through urine. If you’ve come to Newport and seen the sea lions that haul out on some of the docks here in town, and elsewhere – in Astoria there’s a large haul-out of California sea lions as well – these animals like to haul out next to each other. They like to pile on top of each other. When they relieve themselves, they do not seem to mind where it goes. They will expose themselves, and each other, to their body fluids basically.


Miller: Oh, and the bacteria could be in urine, say?

Rice: Correct. That’s probably how it’s mostly transmitted from animal to animal. That brings us to the point where, if you’re on the beach and you’re close to a sick animal and your dog, for instance, is very curious and wanders up to that animal, there’s a chance that the dog could become ill due to exposure to Leptospirosis, primarily through the passage of urine. Sea lions are also thought to get Leptospirosis through open wounds on their bodies, perhaps scrapes or abrasions, or through mucous membranes, which are likely places where the disease can get into the body. But, by and large, urine is probably the most likely means of transmission from animal to animal.

Miller: So what would the potential repercussions be if a dog were to get infected?

Rice: Well, I’m not a veterinarian, so I can’t really comment too much about that. But my understanding is the dog could get sick just the way the sea lion could get sick from it. In which case I would recommend that a dog owner take their dog to a veterinarian and have it examined and diagnosed. It is treatable, but it is a serious disease as well. There are vaccines that are available for Leptospirosis. So a number of dog owners along the Oregon coast – myself included – have had their dogs vaccinated against Leptospirosis, just on the chance that they may become exposed on the beach.

Miller: That’s one proactive, or prophylactic, approach that dog owners could take. What else do you recommend, given the potential risks that these sick or infected sea lions could present to dogs on the beach?

Rice: Well, it’s the same thing I would recommend whether or not Leptospirosis was an issue right now. That is, if you have a dog on the beach, please be mindful of the fact that the beach is also home to wildlife, including marine mammals and birds. It’s really incumbent upon all of us, as responsible pet owners, to manage our dogs and to make sure that they’re not disrupting wildlife. In the spring months – this is a little off topic but – we have an ongoing issue with harbor seal pups that are born on the shore, or close to shore, and they come ashore to get rest. Dogs will unwittingly approach these animals quite often and can cause major disturbances for them. As a general rule of thumb, it’s really best to keep your dog on a leash or at least have it under voice control and be aware of what your dog is up to. It’s easy to just let your dog run loose on the beach and watch them take off. It’s a lot of fun to see your dog getting great exercise that way. But it’s also an issue that we need to take some responsibility, as pet owners and make sure that our dogs are not getting themselves into trouble. It’s again for their own health. They could be getting themselves sick if they end up encountering a sick animal.

Miller: You mentioned earlier that this is a kind of cyclical outbreak – that it’s not the first time that you’ve seen a spike in cases. How does this year, how do the numbers this year, compare to previous years?

Rice: I’ve been here for 17 years. I moved here in about 2006. The first outbreak that I was involved in was between the years 2009 and 2010. We had about 350 California sea lion strandings during that year that we documented. They were not all necessarily attributed to Leptospirosis, but Leptospirosis certainly drove those numbers to that level. We had another outbreak in 2017-2018, another two-year consecutive period, where there are about 200 sea lions that were documented as being stranded during each of those two years. At this stage of the game, right now, we’re looking at over 200 animals likely that have been impacted in some ways or reported as stranding. Our numbers are still coming in. I’m getting two or three animals reported to me every single day, and I expect that this is probably going to continue into December. So we’re probably looking somewhere between the numbers we had in 2009-2010 and the numbers we had [in] 2017 and 2018 – somewhere in the order of 200-some-odd, maybe close to 300, animals overall. So this is looking like a pretty significant outbreak, but we don’t quite know when it’s going to end yet.

Miller: What kinds of calls do you get?

Rice: I get all sorts of calls. Often it’s from somebody who is at their vacation rental. They have just arrived in town and, lo and behold, they look out the window and they see an animal on the beach. They don’t necessarily know if it’s alive or dead, but then they see it move, and they call me. They’re concerned about that animal. I also get calls from people who find a dead animal on the beach, and they just want to make sure it’s been reported. We do our best to document every case of a stranded marine mammal on the Oregon coast. That’s whether it’s alive or dead. These numbers are very helpful. They help us inform the managers with NOAA Fisheries, who oversee the Marine Mammal Protection Act and keep tabs on the populations of these animals nationwide, so these numbers will help with that accounting. I get calls from law enforcement or from state parks rangers. Basically, people who are on the beach who find animals ashore will report them to me in varying states of [inaudible] health...

Miller: In that first example where someone’s in some vacation rental, and they look out, and they see what appears to be an alive but sick marine mammal of some kind. What do you do? What do you say?

Rice: Well, I first ask them for information so I can get as much details as I can about the animal’s condition. And I often ask for pictures. Many people will have a smartphone on hand, and they can easily snap me some pictures and text them to me. I can immediately tell them what they’re looking at and what my thoughts are on the animal. Sometimes it’s just a resting animal that is otherwise healthy and just came ashore to get some rest. But if the animal’s clearly emaciated, clearly not moving properly, has an odd body posture, that will help inform me as to what the animal’s condition is. If it’s a live animal that’s drawing a lot of attention, we can try to get some rangers out from state parks, or some citizen volunteers, to post some signs to alert people to stay back and to leave the animal alone. In some cases we can elect to euthanize animals that are clearly suffering and receiving constant harassment. There are some options in that regard, but by and large, we want to document these cases as best as we can as they come up.

Miller: We had focused on this bacterial infection that can be serious because there is a pretty bad outbreak this year. But what are other reasons that sea lions might end up dead on an Oregon beach?

Rice: Well, there’s a number of other diseases that can affect them, although they’re generally not contagious outbreaks, like we’re dealing with Leptospirosis. So cancer, for instance, will affect a fair number of California sea lions each year, and general types of pneumonia that are often caused by parasites that invade their lungs. Those are common causes of mortality for California sea lions. We also have gunshot wounds that will kill sea lions as well. That’s a fairly regular occurrence, especially on the north coast of Oregon near the Columbia River.

Miller: What are the reasons that somebody would shoot a sea lion?

Rice: Well, I have a hard time imagining it myself. It’s not something I would ever consider doing. But I know that there is a lot of hostility towards sea lions among some folks on the Oregon coast. It’s not uncommon for folks on boats fishing to carry firearms and, in some cases, to take shots at sea lions that they might consider to be at odds with what they do. They may blame the sea lions for taking their fish. But it is a federal offense to kill a sea lion, or to harm one. So it’s certainly not something that can be done legally or openly, but it does happen. We have lots of evidence of gunshot cases over the years, especially with California sea lions.

Miller: Jim Rice, thanks for joining us today.

Rice: Thank you.

Miller: Jim Rice is the stranding program manager for Oregon State University’s Marine Mammal Institute.

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