Sea lions endure leptospirosis up and down the coast (Point Reyes Light, 11.20.2008)

Chompy

Chompy was found by the seawall on Bolinas Beach on Sunday. Her fur is a soft golden brown, but she is emaciated and lethargic. She has an ulcer on her eye, roundworms and diarrhea. When she was offered food, she ate the squid but not the herring.

Chompy is one of several California sea lions currently being treated at the Marine Mammal Center (MMC) on the Marin Headlands in Sausalito.

This year, about 400 sea lions have come through for medical treatment of different ailments such as disease, malnutrition, acid intoxication and trauma. Earlier this fall, masses of sea lion strandings were caused by leptospirosis—a bacterial infection that can be lethal. About 120 sea lion patients suffered from this disease, and the numbers are just now starting to taper off.

“We see waves of it in certain years,” said Sarah Allen, Point Reyes National Seashore science adviser. “It’s cyclical. Some years there are more.”

In Marin County, leptospirosis accounted for half of the strandings in a decade. The majority of these were found in Monterey and Santa Cruz counties between August and November.

Of all the sea lions with leptospirosis treated at MMC this year, only six were stranded in Marin County—at Stinson Beach, Bolinas and Point Reyes National Seashore. All were male, all were juvenile or sub-adult, and most were stranded in September or October. Two survived.

SEA LIONS AND LEPTOSPIROSIS

On any given day, except for midsummer, there are several hundred California sea lions off Point Reyes—either “hauling-out” (congregating on the shore), “rafting” (floating together on the water surface), or “porpoising” (jumping out of the water).

A total population of over 200,000 California sea lions range between Vancouver Island, British Columbia and the southern tip of Baja California in Mexico. Many of them breed on the Channel Islands in Southern California during June and July. Adult males usually migrate north, while the females stay on the southern offshore islands nursing the pups. Younger females—like Chompy—head north as well.

“We lose about 60 percent of our leptospirosis cases,” said Denise Greig, an MMC marine biologist. “In California sea lions, it affects their kidneys, causing renal failure.”

Signs of kidney failure include dehydration, lethargy, seizures due to toxin-buildup, and high levels of phosphorus and waste products. There’s no specific test for leptospirosis, but in a serum chemistry panel, a series of kidney measurements help identify the infection that is transmitted through urine.

MMC is currently studying leptospirosis to understand how the disease spreads and what the risks are to the sea lion population as a whole. They are sampling wild animals throughout their range. “We’re trying to learn what percentage of the population is susceptible. We have a really biased impression here at the mammal center—because we only treat the sick ones,” Greig said. “The question of how our animals at the hospital relate to the whole population is something that we are always trying to understand.”

Over the past 20 years, there’s been a consistent pattern. “Sub-adult juvenile males north of Monterey are the hardest hit,” Greig said.

Is it a matter of geography? Marin County is on the northern end of the disease’s range—it only accounted for about 100 of 1,011 leptospirosis strandings documented in a decade. “It could be timing in terms of migration. That’s why we see them where we see them,” Greig said.

Or perhaps age? “There may be a herd immunity component to it,” Greig said. “The older animals may have been exposed and survived already.” Increases in leptospirosis seem to occur in four or five year cycles. It may not infect large numbers again until there are enough animals in the population that haven’t been exposed. In 2004, there were about 280 cases of leptospirosis.

Or both? “We think there must be an element of sea lion immunity and possibly environmental triggers as well,” Greig said. “Traditionally, epidemiologists like to classify diseases as one way or another—either the disease is present in the population or it comes from the outside. We think we see a little of both in the sea lions.”

For now, there’s no way of saying how much of the entire sea lion population is affected by leptospirosis. Since the 1960s and 70s, the disease has grown proportionally with the growth of the population, with no overall increasing trend.

STRANDED

Chompy’s bloodwork shows elevated levels of two waste products associated with kidney disease. But her phosphorus tested in the normal range, according to Deb Wickham, MMC operations manager. Chompy’s list of ailments is long but she does not have leptospirosis. Like many other marine mammals at the center, her precise disorder may never be known.

On a foggy Tuesday morning, a volunteer tries to put a heat pad underneath Chompy, but she moves away. She had a minor seizure a few hours earlier. Her head shakes from side to side and her movements are awkward. Her back flippers are tucked under her, and she’s shivering. This is the third time she has been stranded. She was released at Chimney Rock on Point Reyes just four days before she was brought in again—this followed a month-long stay at the center after she stranded for the second time, on Pescadero Beach in San Mateo County. She was first found bleeding from the mouth in September on Asilomar State Beach in Monterey County. The working diagnosis for her third stranding includes malnutrition. “It’s never positive when we see them again,” Greig said.

When MMC gets a phone call over their 24-hour rescue hotline, the first thing they do is to get as much information as they can from the caller. “We try to get a picture of the physical characteristics and behavioral condition,” said Erin Brodie from the MMC’s stranding department. “How big is it? What color whiskers does it have? Does it have little ear flaps on the outside? Is it vocalizing? Do you see any injuries?”

Next, a volunteer trained to discern the difference between normal from abnormal pinnipeds behaviors goes to the scene. A sea lion with leptospirosis has a distinctive demeanor and posture. “Sometimes we see them drinking fresh water from pools or creeks where they strand, which is unusual,” Greig said. “And they are sort of tucked up because of the pain in the kidneys.”

In such a case, the stranding department conducts a rescue. A team of volunteers uses a big hoop net with a long cylindrical bag and a drawstring on the end. They throw the net over the animal, then protecting themselves with large shield-like boards with handles called “herding boards,” the team puts the animal into a dog carrier.

At the Center, the veterinary staff examine the animal. Drawing blood from a small vein in a large wild animal requires a restraining process, including a cone-shaped net. “150 pounds of sea lion does not equate 150 pounds of human,” Brodie said. “They’re much more muscular than we are, so they are a lot stronger.”
Someone holds the animal’s head still, putting their knees on either side so that the animal can’t turn its neck and bite the people working around it. Then there are the flipper restrainers. The majority of the strength of California sea lions is in their front flippers, so their shoulders need to be down on the ground and their flippers up off the ground. “When they’re just sitting in their pens, they may look docile, but they’re wild animals,” said Mieke Eerkens, MMC spokesperson. “We do this to protect the animal as well as the people.”

The animals are monitored and released back into the ocean if the bloodwork looks normal, wounds have healed and they have gained enough weight.

The Center is comparatively quiet this week. The last leptospirosis sea lion was found in Tomasini Creek in the Point Reyes National Seashore at the end of October. His name is Tomasini, and he was released back into the wild last Wednesday. He was one of 50 leptospirosis sea lion patients that were released.

Chompy has been released twice—both times at Chimney Rock. The stranding department releases animals in locations that are less populated. “So the animals who’ve been through the stress of rehabilitation and recovering from whatever ailment they have can hang out on the beach for a little bit if that’s what they want to do before going back into the water,” Brodie said. “Chimney Rock is a nice location for the animals to get reintroduced into their natural environment.”

The releases are similar to the rescues. They’re put in a crate and trucked to the beach. “For California sea lions, you open the door and it’s like the last day of school,” said Brodie. “They shoot out and head directly for water.”

If you see a stranded animal, stay at a safe distance and leash your dog. These animals are highly stressed. Please call the Marine Mammal Center hotline: 415-289-SEAL.

~ by Janet Fang on November 21, 2008.

One Response to “Sea lions endure leptospirosis up and down the coast (Point Reyes Light, 11.20.2008)”

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