Zoo InternQuest is a seven-week career exploration program for San Diego County high school juniors and seniors. Students have the unique opportunity to meet professionals working for the San Diego Zoo, Safari Park, and Institute for Conservation Research, learn about their jobs and then blog about their experience online. Follow their adventures here on the Zoo’s Website!
What happens to Zoo animals when they pass away? How can we determine if an animal died of natural causes or had a contagious disease? Well, have no fear because the anatomic pathologists at the San Diego Zoo are prepared to investigate!
InternQuest travelled to the Jennings Center for Zoological Medicine at the San Diego Zoo. The Jennings Center has 5 different departments, all important to maintaining the health and wellbeing of collection animals, and we met two anatomic pathologists. Pathology is a special branch of veterinary medicine that focuses on diseases. Pathologists look at tissue samples from animals to determine what sorts of things may have infected the animal and determine if they are a threat to other animals in the collection.
We met Dr. Jennifer Bernard (left), an Anatomic Pathology Fellow, and Dr. Sabrina McGraw (right), an Anatomic Pathology Resident. Dr. Bernard recently took a test, similar to the test she took to become a veterinarian, and is officially a pathologist! Dr. McGraw only has one more year to go before she, too, can take the test.
Dr. Bernard explained that pathology has two sides: clinical and anatomic. She explained that clinical pathologists, like her, are focused more on living animals and work to treat diseases before they can progress. Anatomic pathologists work with animals that have already died, trying to determine what killed the animal and how it might affect other animals in the collection.
Dr. McGraw presented us with a case to test our pathology skills. The case of the “Coughing Condor” involved a bird that was being treated successfully for lead poisoning but still died, puzzling its keepers. She put a slide containing a sample of the condor’s tissue under the microscope for us to look at. It turns out, the lead poisoning had weakened the immune system of the bird, making it susceptible to infection.
Each slide contains a tissue sample from a different animal. The samples are stained with different dyes to make certain features, such as parasites or fungi, stand out against the animal’s tissues. Once stained, the pathologists can more easily examine the tissue and determine what might have killed an animal.
Dr. McGraw showed us a tissue sample from the “Coughing Condor” case. The teal is the tissue of the condor’s air sac and the pink is a mold called aspergillum. The mold infects a bird when their immune system is weak. This condor already had lead poisoning, so the aspergillum was able to infect the bird, leading to its death.
The skeleton of a small hoof stock was on display, but there was something distinctly different about it. This animal had an extra leg growing out of its pelvis! Dr. McGraw pointed out the different parts of the extra leg and explained that the leg would never have functioned because the muscles wouldn’t have attached to it properly.
We got a special look inside the necropsy lab. Here, animals are dissected in order to determine cause of death in a way somewhat similar to a human autopsy on CSI. The lab is kept very sterile, as technicians have no way of knowing what sort of diseases an animal might be carrying. Necropsies at the Zoo are important for ensuring the health of all animals in the collection.
When larger animals are brought in from the Zoo or Safari Park, a special lift allows for easy transport. The lift can support large animals, up to the size of a rhino! The lift extends all the way to the back of the necropsy lab so that the technicians can place the animal wherever they will be conducting the necropsy.
Before leaving the lab it is important to sanitize any part of your body that came into contact with any part of the lab. Due to the strict protocols of the lab, we were instructed not to lean on any tables or touch anything in the lab. Even though the floors had been washed and disinfected for our visit, we also had to rinse the bottoms of our shoes in a footbath to ensure we didn’t leave with any contaminants on our feet.
A few doors down from the necropsy lab is the histology lab. Here, tissue samples from animals are made into slides that can later be studied and tested. The process is a bit complex, but the technicians and pathologists have it down to a science.
While she showed us the histology lab, Dr. McGraw passed around the skull of a rodent from southern South America known as the plains viscacha. This particular plains viscacha suffered from an infection of the bone marrow known as osteomyelitis. Preservation of tissues and bones allows pathologists to study the different diseases that affected an animal long after it has died. This helps the pathologists learn more about the disease and how to detect it in other animals in the collection.
The histology processing center is essential to turning a tissue sample into a slide. A tissue sample is put in the processing center to extract all the water from it. Once the water is extracted, it is coated with wax. The wax not only makes the sample stronger and easier to handle but also preserves the tissue. Pathologists make slides so that they can take a closer look at what affected an animal and help protect other animals in the collection.
Once a sample has swapped its water for wax it goes to the microtone. Here, the tissue is precision cut and placed on a slide. The microtone can cut a slice as thin as a few cells thick! The thinner the slice the better, as it then becomes easier to look at individual cells and determine what may have been wrong with the animal.
The final step to making a slide is adding stains to it. Each stain is formulated to color a different tissue, fungi, virus, or other components that can infect animal cells. The staining process is automatic and there is a robotic arm that will add stains to the slides. Once the sample has been stained, pathologists have an easier time determining the cause of death for an animal. This is an important part of zoo veterinary medicine because pathologists can more confidently determine what affected and killed an animal, potentially saving other animals in the collection.
Libby, Photography Team
Week Six, Winter Session 2014