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Fish Stories
Comparative Medicine's veterinarians look after the health of animals at local institutions

At the National Aquarium in Baltimore, from left, vets Tim Cooper, Chris Zink and Brian Simons.
It was just before the 11 a.m. show, on the morning of July 25, when Bridgit, a 4-month-old dolphin, was found dead at the bottom of the pool in the Marine Mammal Pavilion at the National Aquarium in Baltimore. Aquarium scientists were mystified. For several years, they had run a successful breeding program, but Bridgit was the second dolphin calf to die this year. What was going on? For the answers, they turned to Hopkins’ Department of Comparative Medicine.

The department’s postdoctoral fellows have been conducting postmortem examinations on marine mammals at the Aquarium ever since it opened in 1981. They perform similar exams for the Baltimore Zoo, where they’ve done them on every animal that’s died in the last 20 years, and for Johns Hopkins, which has its own large and varied supply of research animals. As a result, the Johns Hopkins University Department of Comparative Medicine now boasts the greatest variety of species examined of any comparative medicine department in North America.

What’s the point in all this? “By understanding how animal diseases are caused, we gain a better understanding of human disease,” says Christine Zink, professor of comparative medicine and Hopkins’ chief liaison with the Zoo and the Aquarium. “That’s what comparative medicine is all about.”

Zink cites examples of human-like diseases that are currently being investigated: a chronic neurological disease that resembles HIV in giraffes; a herpes virus, discovered and studied here by a postdoc about six years ago, which is killing elephants worldwide.

Bridgit’s affliction, it turns out, was far more common. She had pneumonia. But she’d also been repeatedly roughed up by older males. “Which came first—the roughhousing or the pneumonia—we don’t know,” says Brian Simons, the postdoc who examined Bridgit.

The other dolphin, a 10-day-old male who died in April, had bacterial meningitis. “We found that the dolphin had not gotten enough colostrum from its mother,” says postdoc Tim Cooper, referring to the antibody-rich fluid secreted during the first days postpartum.

Like the other postdocs in Comparative Medicine, Simons and Cooper are veterinarians who are undertaking further training in comparative pathology. The first year of their program is devoted to the autopsies, known as necropsies, because they are done on animals. The following three years are spent on research projects, supported by a longstanding NIH training grant. More than 100 veterinarians have gone through the program, and many are now department chairs and leaders in academia and industry in the United States, Canada and Europe.

The postdocs have at their disposal confocal microscopy and other state-of-the-art technology that can help them ascertain what’s going on at the molecular level, instruments not generally available at zoos and aquariums. That is one reason why most of the animals, except for the really big ones, are sent to East Baltimore to be examined.

Big animals don’t work well in East Baltimore. The vets learned that the hard way when, years ago, the Aquarium had a beluga whale that died of what appeared to be an acute viral infection. It was shipped to Hopkins. The whale was so big, it could not entirely fit into the lab. Its tail stuck out the door; its blood ran out into the hall and down to the elevator bank. Those who worked in a nearby office—the Dean’s Office, no less—were not amused.

But even some smaller animals have caused problems, notes Zink, recalling the time when dozens of snakes of all types, including some very poisonous ones, were dying at the Baltimore Zoo. Like organs ready for transplant, the dead snakes were sent over on ice in a cooler. They were no longer venomous because their heads had been cut off. But, much to the amazement of Zink and others in the lab, when the snakes thawed, their headless bodies began to writhe.

The necropsies, explains Zink, help institutions identify diseases before they become outbreaks. The snakes had Paramyxovirus infection, which is similar to measles in humans. Penguins at the Zoo are susceptible to malaria, carried by songbirds. Almost every spring, a penguin dies. The Hopkins vets check out the spleen. If they detect malaria, the penguins are observed individually and treated if necessary.

At the Aquarium’s request, Hopkins vets now will necropsy all its animals. That means not just aquatic animals, but also reptiles, birds, and furry mammals, like monkeys and sloths. The Aquarium is opening an Australia exhibit next year. So it looks like Comparative Medicine will be adding to a list of species examined—one that already includes everything from tarantulas to elephants—crocodiles, flying foxes and blue-tongued skinks. (That’s a type of lizard, in case you were wondering.)

—Anne Bennett Swingle



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