Learning from Flipper

Sunrise sends streaks of red, violet and orange over the rippling surface of San Diego Bay at Naval Base Point Loma, where 25 undergraduate interns are getting started on the day’s work. They hose down a gently swaying jigsaw of floating docks and pack 10-gallon thermoses with herring, capelin, smelt, mackerel and squid that will fortify their charges—in this case, 60 bottlenose dolphins that intermittently pop out of the water like prairie dogs.

This seaside installation is home to the U.S. Navy’s Marine Mammal Program, which in the late 1950s studied how dolphins whip through water, with the goal of improving torpedo, ship and submarine design. Today the Navy trains two species, the bottlenose dolphin and the California sea lion, to help guard ports, personnel and military vessels around the globe. They have served in Vietnam and Iraq.

Because dolphins possess the most sophisticated sonar known to man, they are unrivaled in their ability to locate and disable anti-ship mines and booby traps, even in the murkiest waters. Sea lions, with their superb low-light vision and sharp underwater directional hearing (something humans lack), can detect a potential enemy combatant swimmer approaching a ship. Even more importantly, both species can make repeated deep-water dives without suffering the decompression sickness that humans do.

What this means is that a single marine mammal, two handlers and a rubber boat can provide the same high level of security as a team of human divers and the naval vessel, crew, physicians and medical equipment needed to keep them from getting “the bends.” [See “Sea Mammals on a Mission.”]

So when it comes to providing for these soldiers of the sea, it’s nothing but top-flight.

The National Marine Mammal Foundation is the nonprofit charitable organization that provides medical care for the Navy’s marine mammals. Cynthia Smith, V99, is the executive director and medical director of the foundation, which cares for 120 Navy dolphins and sea lions, ranging in age from newborns to senior citizens.

Foundation employees, the U.S. Navy, the U.S. Army, other contractors and consultants staff the $20 million operation at Point Loma, where the animals live and are trained in pens submerged in San Diego Bay. Eleven full-time veterinarians and 160 trainers tend to every need of this marine security force. The dolphins and sea lions even have personal chefs: Army veterinarians inspect seafood from all over the world to supply the one million pounds of fish they consume each year.

On this day, Smith, who has cared for the Navy mammals for more than a decade, arrives on base promptly at 7:30 a.m. Because the animals get so much exercise swimming in the open ocean, her job is a lot like that of physician for a team of Olympic athletes.

It is also somewhat like treating patients from another planet; although scientists have been studying marine mammal physiology for more than a century, little is known about them relative to the landlubber animal kingdom.

Take sea lions, which Smith says are like water dogs, so “small animal medicine comes in really handy.” Dolphins, on the other hand, she says, are more of a physiological patchwork of people, pigs and cows.

It is those similarities between dolphins and humans, learned by studying and caring for these animals for nearly a half-century, that have yielded an unanticipated benefit—a robust mountain of data that is helping to advance human medicine. One tantalizing outcome currently under investigation could lead to a treatment or cure for the 23.6 million Americans who suffer from type 2 diabetes.

“Think about it,” says Stephanie Venn-Watson, V99, the veterinary epidemiologist who heads the clinical research enterprise at the National Marine Mammal Foundation.

“How many blood samples do we, as people, give in a lifetime? Well, compare that with these animals, which routinely provide blood samples, have daily health inspections, get annual ultrasound examinations and have access to numerous diagnostic tests over 30 or 40 years,” she says. “The power of the database is endless. We haven’t found the limit to the questions we are able to ask.”

Fifty Is the New Thirty

The first fragments of that longitudinal database were incubated at an amusement park in Santa Monica in 1960. Sam Ridgway, an Air Force veterinary officer stationed at nearby Oxnard, would tag along with the local vet, Robert M. Miller, to care for the dolphins and seals that performed at Pacific Ocean Park.

They published a few of their cases in professional journals, including the first X-ray of a live dolphin. Ridgway, now regarded as the father of marine mammal medicine, was also assigned to serve on two naval bases, where he first met the military and civilian scientists who were interested in studying the mechanics of how dolphins swim so fast and dive so deep.

After completing active duty with the Air Force in October 1962, Ridgway was hired as the animal health officer for the Navy’s first five bottlenose dolphins. Soon after, he landed on a technique that is now the cornerstone of the Navy’s marine mammal care regimen.

In 1963, the Washington University physicist C. Scott Johnson trained a dolphin he was using in his auditory research so that Ridgway could do a complete physical examination without removing the animal from the water. Under the leadership of Ridgway, now president of the National Marine Mammal Foundation, the practice of training marine mammals to participate in their medical care has been refined in the decades since.

“The goal is to keep the animals comfortable and in their natural environment at all times,” says Smith.

The Navy mammals can contract the same illnesses that affect their relatives in the wild: respiratory infections, diarrhea and other bacterial and viral diseases. The focus on preventive care and rapid detection of illnesses has been so successful, however, that the veterinarians are developing a geriatric medicine program.

Many Navy dolphins are now in their 30s and 40s; some are even reaching 50. That’s ancient compared with dolphins in the wild, which typically live into their teens and 20s. Navy sea lions live two or three times longer than their wild counterparts.

Dolphins give blood samples, have their temperature taken and provide fecal and urine samples—all while in the water. As semi-land animals, sea lions undergo the same tests while lounging on the floating docks in San Diego Bay.

Checkup in the Water

This morning, Smith pauses on the dock next to Mu, a 33-year-old dolphin. Mu rolls onto one side, bobbing in the water as a veterinarian runs a portable ultrasound over her belly. Four months pregnant, Mu is one of six Navy dolphins due to calf this summer.

“It’s an exciting but anxious time,” says Smith, who pauses to borrow a pair of high-tech sunglasses from the attending vet, Forrest Gomez. The ultrasound image projects onto the inside of the lenses, allowing Smith to assess the growing fetus despite the harsh sunlight bouncing off the waves.

Prenatal ultrasounds are rare in traditional veterinary practice, so the foundation team looks to human medicine as the standard. “We do ultrasounds at least once a month at this stage [of pregnancy],” says Smith. “We check for a fetal heartbeat and look at fetal development. As the due date approaches, we do more frequent ultrasounds.”

Pleased with Mu’s progress, Smith joins the rest of the medical team for a discussion of the day’s cases. After 15 minutes of rounds beside the bay, the group gathers inside the on-site naval veterinary hospital to review two special cases.

In the last month, the veterinarians worked with two interventional radiologists at Naval Medical Center San Diego, the human military hospital, to check the lungs of two dolphins—one treated for a bacterial abscess and the other for a fungal infection. Jenny Meegan, another foundation vet, pulls the dolphins’ CT scans up on a computer monitor and shares the human doctors’ interpretation of the results: both animals are recovering nicely.

“Having that perspective and direction on cases is so helpful,” says Eric Jensen, the Navy Marine Mammal Program’s managing veterinarian. “Comparative veterinary medicine is not new. But the concept of ‘one health’—uniting veterinary medicine and work in the human health fields—has been gaining great momentum over the last four or five years,” he notes. “And unlike your average veterinary clinic, we get to regularly work with specialists in the human field, thanks to our access to Navy and Army physicians. Those resources really elevate our wellness program.”

For the CT scans, the dolphins traveled to the human naval hospital and underwent the procedure just like human patients do. “Our animals are trained to voluntarily beach and be transported all over the world,” says Jensen. “So they have no problem going into a human hospital—though they do tend to draw a bit of a crowd. We just roll them down the hall [on a gurney], lay them down [on the plastic-covered CT machine] and clean up thoroughly afterwards.” To prevent overheating, the dolphins are continually kept wet with sponges or spray bottles.

In addition to providing direct care to the Navy marine mammals, foundation veterinarians also work on special projects to solve particular clinical problems in marine mammal medicine or to research disease pathology.

Smith and Venn-Watson, for example, have enlisted a group of experts in veterinary and human medicine from the University of Texas Southwestern, the University of California, San Diego, Dolphin Quest and SeaWorld San Diego to determine why dolphins develop kidney stones. The project was inspired by Rake, a geriatric male dolphin that went into renal failure five years ago.

While creating a treatment plan for Rake, “we talked to other [marine mammal] facilities and people working with wild animals to see if kidney stones had similarly affected any dolphins they’d seen,” says Smith. “As soon as we realized it was a health problem impacting many dolphins, it became a collaborative effort to learn why, and how to prevent and treat it.”

The multidisciplinary research team since has discovered that low levels of citrate in the urine may be a risk factor for kidney stones in dolphins—and that appears to be the case in humans, too. They are now working on pinning down the cause of this condition, known as hypocitraturia, with an eye toward developing a treatment for dolphins.

An Alternate View of Diabetes

The similarities between dolphins and humans mean that many advances in dolphin medicine could influence how physicians understand and treat human diseases.

Venn-Watson, a veterinary epidemiologist who holds an M.P.H. from Emory University, said the information contained in the Navy’s marine mammal database significantly surpasses the breadth of any population study she encountered during her two years traveling the world as a project director for the World Health Organization’s Global Foodborne Infections Network.

Even a seemingly routine study can yield unimaginable results.

Consider this simple exercise. Venn-Watson compared more than 1,000 fasting and post-feeding blood samples taken from 52 dolphins over seven years. She was surprised to find that the dolphin data did not match similar studies in other animals. Instead, the blood changes in these dolphins mimicked those seen in large-scale studies of people with type 2 diabetes.

We humans need plenty of glucose, a sugar transported through the blood, to feed our big brains. The hormone insulin helps our bodies regulate the metabolism of carbohydrates and fats. People with type 2 diabetes either do not produce enough insulin or are immune to insulin’s effects, promoting the buildup of too much glucose in their blood, a condition known as insulin resistance. This blood sugar overload can lead to severe health problems, including heart disease, stroke, blindness, nerve damage and kidney failure.

Like humans, dolphins have large blood sugar demands because of their large brains. But unlike humans, insulin resistance in dolphins may be advantageous.

“Amazingly, dolphins are diabetic-like when they need it and non-diabetic when they don’t,” explains Venn-Watson.

Dolphins seem to activate insulin resistance, causing temporarily high blood sugar during short overnight fasts, she says. They then revert to a non-insulin-resistant state as soon as they eat a meal.

“If we can find and figure out how to flip that switch off and on in humans, that could be a great benefit to people with diabetes,” she says.

Venn-Watson believes that dolphins may have evolved this way to stretch the limited stores of glucose found in their extremely high-protein, low-sugar diet, which consists entirely of fish. That notion is supported by research that Ridgway conducted in the 1970s. When dolphins were fed sugar, they had high glucose levels that lasted up to 10 hours. Those studies showed that dolphins’ diabetes-like systems do not have the ability to handle high-sugar meals.

The foundation is now working with the nation’s leading diabetes research institutes, including the Salk Institute for Biological Studies in La Jolla, Calif., to identify that genetic on/off switch in hopes of eventually testing a diabetes cure in mice and then in humans.

Looking for a Breakthrough

This one-health strategy is catching on. Last winter, the National Marine Mammal Foundation welcomed 40 scientists from around the country, more than half of them from human medicine, to brainstorm new research projects. The gathering generated a five-year strategy and a prioritized list of studies in geriatric health, metabolic diseases and infectious diseases.

“My job is to take that research road map and bring it to life,” says Venn-Watson. Her typical work week involves reaching out to potential collaborators from the human medicine side. The good news is that many are eager to invest their time and expertise in work that could advance both dolphin and human health.

For example, foundation veterinarians and human medicine researchers are collaborating to assess whether changes such as mild chronic inflammation, high cholesterol and decreasing muscle mass seen in aging dolphins—which mimic changes seen in aging humans—are associated with particular health problems and if targeted therapeutics can improve the quality of life in their golden years.

“That kind of breakthrough would be a win-win for animals and humans,” says Venn-Watson. “This is one health. By caring for one species, we can care for many.”

This story first appeared in the Spring 2011 Tufts Veterinary Medicine magazine.

Genevieve Rajewski can be reached at genevieve.jajewski@tufts.edu.