Volume 7 of Evotis features some of our programs and projects taking place in California. Several of these are the product of years of collaboration, while others are in their infancy.

The Oiled Wildlife Care Network, which has been caring for wildlife in oil spills since the 90s, was called into action this Spring when a coastal pipeline ruptured in Santa Barbara, threatening the lives of many sea lions, pelicans and more. Meanwhile, the team is currently expanding their response efforts to cover inland oil spills as well, in response to the rapid rise of oil transport by rail in the wake of fracking. This volume also features a project about a cat parasite that kills sea otters -- a massive team effort that illustrates the collaborative foundation of the Karen C. Drayer Wildlife Health Center and the One Health Institute. To receive future volumes, subscribe!

how a cat parasite kills otters

a lake toxin that poisons the sea

Oil by Rail & danger for wildlife

video: into the refugio oil spill

tracking pelicans post-oil spill



toxoplasma gondii sea otters














toxoplasma gondii sea otters














How a Parasite in Cats is Killing Sea Otters

The Journey of Toxoplasma Gondii

How is it that a parasite transmitted by cats on land can contribute to the death of sea otters in the ocean?

The answer lies in a parasite called Toxoplasma gondii and the journey it takes from cats, through the environment, and then to wild marine mammals. It’s a story worthy of our attention, because humans play an active role in the process, and have the potential to fall ill to the same parasite.

Here you see Toxoplasma gondii's complex journey from prey species to cats to the sea (or to humans or livestock). Oocysts are key ingredient in that transport.

Toxoplasma gondii is a parasite that can infect virtually all warm-blooded animals, but the only known definitive hosts are cats – domesticated and feral house cats included. Cats catch the parasite through hunting rodents and birds and they offload it into the environment through their feces.

Between 15-18 percent of the U.S. human population actually carries Toxoplasma. The human body does not fight it off, so the parasite remains dormant in muscle or nervous tissue, usually causing little to no harm. That is unless your body is immunosuppressed in some way, in which case the parasite can become reactivated, leading to illness and even death. This has been the unfortunate case for many AIDS patients.

Oocysts are egg-like structures that are released by cats in their feces – formed from the sexual multiplication of the parasite, which only occurs in the gut of the definitive host. Once infected, cats can release hundreds of millions of Toxoplasma oocysts in their feces, for up to two weeks.

Dr. Karen Shapiro working in the Monterey Bay.

Dr. Karen Shapiro working in the Monterey Bay.

Pregnant women are often told to avoid contact with cat litter for this reason – a mother who is infected during pregnancy can pass the infection to her unborn child, which can result in devastating disease in the fetus.

Oocysts are robustly resistant to environmental insults, which renders Toxoplasma stable in cold water for years. When the oocysts reach the ocean, they attach to kelp and marine snow in the seawater, at which point they can incorporate into the marine food web. Sticky substances excreted by seaweed allow the oocysts to directly adhere to kelp, the preferred food of turban snails. Oocysts are then accidentally ingested by snails, which are subsequently preyed upon by the sea otters. The journey from cat to sea otter is complete.

Otters can also ingest oocysts through grooming and other prey items. Scientists recently detected Toxoplasma in green-lipped mussels from New Zeland intended for human consumption.

How can you prevent it?

There are three main factors that can contribute to Toxoplasma infections in sea otters:

  • Domestic cats: studies by the Karen C. Drayer Wildlife Health Center show that domestic cats contribute oocysts to coastal watersheds.
  • Loss of wetlands: The destruction of wetlands leads to the loss of filtering capacity, which could otherwise keep fecal pathogens from running into the sea.
  • Water runoff: Our cities are built on impervious surfaces; rain that falls on cement creates more runoff than rain that falls on natural earth, which contributes to increased runoff that can carry fecal pathogens to the sea.

With those risk factors in mind, what can people do to alleviate the problem?

Keep cats indoors, and if you do allow your cat outdoors, it’s a good idea to have litter boxes both inside and out. That way feces never actually enters the environment. If your cat does poop outdoors, collect and dispose of it by placing it in a plastic bag before putting it in the trash.

Spay or neuter your pet cat. A lower domestic cat population means that there are fewer cats roaming around to catch and spread Toxoplasma.

Support wetland conservation and reconstruction, as well as other natural lands that border our oceans.

Think green when designing your home or landscaping your yards. Leaving as much natural cover as possible will help rainwater trickle back into aquifers instead of generating runoff.

A Cautionary Tale

No problem occurs in isolation. The contaminants that humans and their domesticated animals contribute to the environment can have a lasting effect that stretches beyond their backyard. In that sense, Toxoplasma is probably only the tip of the iceberg. If a cat-derived parasite can sicken or kill sea otters, what other pathogens are moving through the environment and into the ocean?  And what health effects are they having, now or in the future, on marine animals and people?

The One Health approach, in which animals, people and the environment are all studied in confluence, will prove crucial in answering these challenging questions.

By Desiree Aguiar, Karen Shapiro, Justin Cox and Christopher Ancheta.

Support the Karen C. Drayer Wildlife Health Center


cyanobacteria otters pinto lake












Photo by Kama Guesalova

cyanobacteria otters pinto lake












Photo by Kama Guesalova

Cyanobacteria: Lake Toxin Poisons the Sea

By Jasjeet Dhanota

When sea otters with bright yellow gums started turning up on beaches in California’s Monterey Bay, Dr. Melissa Miller took notice. The first of these otters showed up 2007, and by year’s end 11 more were found dead with similar conditions.

“As we started doing the post-mortem examinations on some of these otters, we could see that the livers were very swollen and had areas of hemorrhage,” said Dr. Miller, a veterinarian and wildlife pathologist for the California Department of Fish and Wildlife Marine Wildlife Veterinary Care and Research Center. “In some cases, even if the animal had just died, we would lift the liver out of the abdomen to take a closer look and it would literally fall apart in our hands.”

After extensive testing, Dr. Miller, an affiliated faculty member of the Karen C. Drayer Wildlife Health Center at UC Davis, and her team determined that the culprit behind the yellow sea otters was a total head-scratcher — microcystin, a toxin produced by the freshwater cyanobacteria Microcystis, which is also commonly referred to as blue-green algae.

Sea otters live in the salt water of the Monterey Bay, so how could they be ingesting a deadly freshwater toxin?

Just over five miles inland from the Monterey Bay, Pinto Lake in Watsonville has been experiencing a series of wicked cyanobacteria blooms that leave the lake’s waters slimy and green.

Aside from the blooms, Pinto Lake is a treasure. It’s one of just four natural lakes in the Monterey Bay region, and it attracts a variety of waterfowl each year. Robert Ketley, a water quality program manager for the City of Watsonville, describes it as “drop-dead gorgeous.”

Yet, due to a series of manmade changes to the watershed starting in the 1850s, the Pinto Lake ecosystem has grown unstable over the years. Deforestation of the surrounding redwoods and local development have caused the water level to rise and nutrient-rich sediments to enter the lake. Meanwhile, agricultural practices have increased the fertilizer runoff into the water. As a result, the lake’s natural balance has shifted, causing large cyanobacteria blooms to begin in the 1970s.


Pinto Lake flows into Corralitos Creek, which then connects with the Pajaro River. The Pajaro River empties into Monterey Bay, creating a connection between the freshwater cyanobacteria blooms and marine wildlife. The result: yellow otters with failed livers.

It’s important to note, however, that Pinto Lake is not the sole perpetrator of cyanotoxins into the seas.

“I never want people to think that all of the otters died because of Pinto Lake,” said Dr. Miller. “Because that’s absolutely not true.”

The issue of cyanobacteria is widespread along the California coast and around the world. Recent studies have found it in the San Francisco Bay and at the mouth of the Klamath River.  In cities like Toledo, Ohio and Wuxi, Jiangsu Province, China, severe Microcystis blooms led to local drinking water crises.

“While Pinto Lake is a particularly relevant example, we see cyanobacterial blooms and toxins in every state and nearly every water body, from seasonal wetlands in California to Lake Erie,” said Dr. Raphael Kudela, a professor of Ocean Sciences at the University of California, Santa Cruz. “It truly is a problem that is in everyone’s back yard.”

Dr. Miller, however, was able to specifically link the toxins she was finding to the blooms at Pinto Lake, so she reached out to Ketley and the two have been working closely ever since.

“Individually, we could have gone on and done our various things,” said Ketley. “But it’s only by getting together, telling our stories together, finding our connections, that this has become so much more.”

Every fall, Pinto Lake's microcystin levels spike way beyond what's considered dangerous for humans and animals.

Today, the blooms continue to pose a significant health risk for people and animals in the area.

“In mammals, including humans, chronic exposure can lead to increased risk of cancer, while acute exposure can give you jaundice-like conditions, and at high enough concentrations can cause death,” said Dr. Kudela. “We can be exposed to the toxins through drinking water, consumption of algae, and even through breathing in toxins that become aerosolized.”

News stories of dogs dying from the toxin are not uncommon throughout the U.S. Dogs that swim in a body of water are often inclined to drink it without regard for the dangerous bacteria. Immediate treatment is vital, because there is no antidote for the toxins.

Fortunately, Cyanobacteria can be managed. Treatments have been proposed to trap excess phosphorous in the lake, and correcting this nutrient imbalance will reduce the amount of bacteria that grows there. In the long-term, the goal is to reduce agricultural runoff and improve watershed management to prevent future cyanobacteria superblooms. Small cyanobacterial blooms should always be expected, but it is possible to reduce the magnitude.

A solution may also arrive in the form of the Safe Water and Wildlife Protection Act of 2016 (AB300), which is a bill proposed in the state of California. If passed, it would create a centralized, comprehensive task force to respond to cyanobacteria blooms throughout California, including Pinto Lake.  

Meanwhile, veterinarians, community members, local government and growers are taking an interest in the issue and doing what they can, whether that is spreading the word, continuing their research or changing behaviors.

“Each and every one of them has a critical role to play and things they can bring to the table,” said Ketley. “Expertise, resources—everybody is valuable.”

The effects of cyanobacteria blooms are widespread, so managing the problem requires collaboration between many different fields. Human activities on the mainland trickle down to the ocean, impacting the health of wildlife and the environment.

“It’s a classic One Health problem,” said Dr. Miller. “We have to get together as a group and figure out what to do for the long-term.”


Support the Karen C. Drayer Wildlife Health Center


pelican tracking refugio oil spill














pelican tracking refugio oil spill














Tracking Oiled Pelicans After the Refugio Oil Spill

The Oiled Wildlife Care Network, a program of the UC Davis One Health Institute, placed satellite tracking devices on 12 brown pelicans affected by the Refugio Oil Spill, which dumped 100,000 gallons of thick crude oil along the coast near Santa Barbara in May. The pelicans were rescued and cleaned for several weeks after the spill before being released back into the wild. The tracking devices will monitor the birds' survival and help scientists see if they return to normal behaviors (like breeding ) after having been oiled. Watch the video to see how the pelicans' movements are tracked.


Support the Oiled Wildlife Care Network













Photo by David A. Mitchell












Photo by David A. Mitchell

Rehabilitated Bald Eagle Returns to the Wild

An adult female bald eagle was rescued by the Shasta Wildlife Rescue after unknown trauma in northern California. She was rehabilitated at the California Raptor Center at UC Davis for four weeks and released back where she was found, east of McArthur, California off of Highway 299. Watch her sail into the wild in this footage.

Support the California Raptor Center