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wildlife disease laboratories

78

A Successful Giant Panda Workshop

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Dr. Megan Jones (left) and the author (right) had a chance to see how San-Diego-Zoo-born Yun Zi is doing. (Answer: Fantastic!)

Unlike many of my San Diego Zoo Global (SDZG) colleagues that have traveled to China, I wasn’t sent there to accompany one of our young pandas on their journey home. Mine was unlike any other China trip. Situated in the heart of China lies a small city with just over 600,000 people. The city of Dujiangyan is in the Sichuan Province, just 45 miles from Chengdu, the country’s 7th largest city by population. The Sichuan province is best known for their extremely spicy food, and one other thing, the giant panda!

This connection was obvious from the moment I stepped off the airplane. Littered throughout the airport are panda souvenir shops, mock habitats filled with plush giant pandas, and tourists decked out in panda garb. Several street corners in Dujiangyan are decorated with oversized giant panda statues arranged in various “panda-like” postures. Just about anything you can imagine has a panda on it. You want a panda pot holder or shower curtain? You got it—you can even pick up panda green tea and panda cigarettes.

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The workshop was held at the Dujiangyan Panda Base hospital in Sichuan.

Late last year, Dr. Megan Jones, a SDZG veterinary pathologist, and I set off to China to teach a Giant Panda Pathology International Exchange training workshop in Dujiangyan. Working with the recently built Dujiangyan Giant Panda Rescue and Disease Control and Prevention Base, which aims to rehabilitate sick and geriatric giant pandas and red pandas, we were tasked with teaching the first of a series of workshops intended to share knowledge and skills in wildlife disease surveillance, investigation, and research.

The beautiful and green-certified facility is located on 125 acres along the foothills of the bamboo forest and currently houses almost 30 giant pandas. The facility also contains a public education center filled with many creative and unique hands-on activities, including a real giant panda skeleton and—my favorite—a digital, interactive, panda necropsy table complete with an overhead surgical lamp!

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The beautiful facility was just the right venue for participants to sharpen their necropsy skills.

The pathology workshop was comprised of 25 Chinese veterinarians, managers, and technicians from 18 different panda facilities throughout China, as well as 4 interpreters and 9 instructors from various international facilities. The main focus of this workshop was developing necropsy, or post-mortem exam, skills through a series of lectures and hands-on wet labs. Necropsies are an essential tool for making accurate diagnoses and ultimately determining the cause of death, just like a human autopsy. The lab portion of the workshop enabled the participants to hone their necropsy skills using rabbits. These skills include taking accurate measurements and photos, practicing proper tissue sampling techniques for histology and future testing, and ensuring all gross lesions are accurately described and recorded in the final report.

These tools and techniques will help the Chinese determine the best conservation strategies for the giant panda populations in China. This workshop has been in the making for over 20 years! Thanks to the hard work of many experts in the field, including SDZG’s Wildlife Disease Laboratories Director, Dr. Bruce Rideout, as well as the China Conservation and Research Centre for the Giant Panda, disease investigation will become an integral part of panda conservation, a necessity for any conservation plan.

This is just another great example of how the San Diego Zoo is helping the fight against extinction globally.

 

Megan Varney is a research technician with the San Diego Zoo Institute for Conservation Research.

1

Bones on the Beach

The team repositions the whale skull for better access for cleaning, measuring, and sample collection.

The team repositions the whale skull for better access for cleaning, measuring, and sample collection.

The Wildlife Disease Laboratories of the San Diego Zoo Institute for Conservation Research and the San Diego Natural History Museum (SDNHM) have had a long-time working relationship. So when Scott Tremor, the mammologist at SDNHM and a long-time friend of mine, called me in March to tell me about his latest adventure and make an interesting proposition, we were intrigued. A 30-foot-long juvenile humpback whale had died, and the carcass had washed ashore at Pelican Point, on the tip of Point Loma. Humpback whales are relatively rare off San Diego’s coastline, so the museum wanted to preserve the specimen for its collection. It had laid on the beach in the sun for over a month, and Scott was collecting volunteers to help clean the bones.

Having never necropsied a whale and being unfamiliar with the anatomy, I thought it would an amazing experience. This rare opportunity also enticed a few coworkers and two pathologists (Dr. Jenny Bernard, Dr. Andrew Cartocetti, Megan Varney, and Rachael Keeler) to put on their Tyvek® suits and boots and help out. With the warning that the carcass may have washed away overnight and may not be there when we arrived, we met up with other volunteers at the San Diego Natural History Museum and headed to the beach.

Pelican Point is a relatively narrow beach surrounded by a high cliff. This beautiful spot, part of Cabrillo National Monument, is closed to the public—the only way to reach it is down a cliff wall using a knotted rope. We timed our excursion to coincide with low tide, so we could access the beach and the whale. There, we were met by Southwest Fisheries Science Center employees, who are responsible for testing tissues and collecting measurements on all beached cetaceans. Dr. Thomas Deméré, curator of paleontology at the SDNHM, led us through the process. One of his areas of expertise and interest is in the evolutionary history of baleen whales, also known as the mysticetes. He explained that baleen species (humpback, fin, blue, minke, right, and grey whales) are filter feeders, but have all evolved different feeding strategies. Fossil evidence shows that all baleen species evolved from toothed whales. In studying today’s mysticetes , scientists have discovered that baleen whale embryos develop upper and lower teeth that simply never erupt. At some point the teeth are reabsorbed and baleen is formed. Because baleen is made of keratin, it rarely fossilizes and has not been studied much—making it important on this excursion to comb the beach in search of the sloughed baleen in addition to recovering the whale’s bones.

When we arrived, the whale looked like a white-grey mound. The goal of the day was to disarticulate the skull from the body and move it to the base of the cliff. Naturally, the tide washing over the carcass had removed some of the flesh exposing some bone, but there was still a lot of work to be done. The soft, rubbery flesh was hard to cut through and the sand dulled our knives immediately. Tom was amazing at directing us the best way to maneuver the skull so we could cut away the muscles. In the end, the strength and endurance of so many people accomplished our goal; we separated and lifted the 300-pound skull to a safe place on nearby rocks. All the while, a pleasant breeze of fresh ocean air kept the smell away. It wasn’t until later in the car ride home we realized we smelled like the hold of a fishing boat!

As you would expect, Scott and his volunteers made many more trips to the beach to recover as many bones as possible, stacking them at the base of the cliff. On April 14, the skull was placed in a sling, and the U.S. Coast Guard airlifted it first to a nearby parking lot, then on to a spot where it was buried so local insects could finish cleaning the bones. All of the other bones were carefully moved assembly-line style by a group of volunteers. It was front-page news in the local media that day! What a great opportunity we had collaborating with our neighbors at the San Diego Natural History Museum to turn a tragedy into valuable learning experience.

 

April Gorrow is a senior pathology technician at the San Diego Zoo Institute for Conservation Research. Read her previous blog, Nature’s Excellent Engineering Feat: The Egg.

158

Pathologist’s Report on Gao Gao’s Tumor

On the left is the paraffin wax block containing the processed tumor tissue, which is then cut into thin slices (about the width of a human hair) by our histotechnologist. These thin sections are then stained by several different methods to allow microscopic evaluation of the cells in the tumor.

On the left is the wax block with the processed tumor tissue, which is then cut into thin slices (about the width of a human hair). These thin sections are then stained by different methods to allow microscopic evaluation of the cells in the tumor.

As most of you know, giant panda Gao Gao had surgery May 6, 2014, to remove his right testicle after a tumor was discovered by our veterinary staff (see Surgery for Gao Gao). Since that time, we have received a lot of questions about how Gao Gao’s diagnosis was made and what the findings mean for his long-term prognosis. In this blog I’ll tell you about our analysis of the tumor in the Wildlife Disease Laboratories of the San Diego Zoo Institute for Conservation Research and what we know about the tumor in giant pandas and other animals.

After we received Gao Gao’s testicle in the laboratory, parts of the tumor were processed and stained for examination under a microscope. From this, the veterinary pathologists gathered clues from the arrangement and distribution of tumor cells, features of individual tumor cells, and the frequency of tumor cell division and invasion into adjacent normal tissues.

This photomicrograph (taken through a microscope) shows the tumor on the right-hand side compressing the normal testicular tissue on the left.

This photomicrograph (taken through a microscope) shows the tumor on the right-hand side compressing the normal testicular tissue on the left.

We also used a specialized technique, immunohistochemistry, to determine if the tumor was making substances characteristic of one particular cell type or another. All of this information was synthesized to determine the tumor cell type and if the tumor was completely removed.

In Gao Gao’s case, the evidence supports a diagnosis of seminoma, which is a tumor arising from the germ or sperm-producing cells. In addition, there was no evidence in the surgically removed tissues of tumor spread beyond the testicle. In domestic animals, seminomas are common in older dogs, and they are usually completely cured by surgery. However, in other species such as humans, a higher percentage of seminomas will metastasize (spread) to other organs without additional treatment such as chemotherapy.

This high magnification photomicrograph shows a single tumor cell undergoing mitosis (cell division), a characteristic that indicates tumor growth. The dark purple material at the center of the cell is the nucleus beginning to divide.

This high magnification photomicrograph shows a single tumor cell undergoing mitosis (cell division), a characteristic that indicates tumor growth. The dark purple material at the center of the cell is the nucleus beginning to divide.

So what does this mean for Gao Gao? The answer is that we can’t tell for certain if his tumor has been cured by surgery or if there is a small chance that it could reoccur at a later time. This is a common problem for pathologists who work with endangered animals, because very few tumors will ever be observed in these species, whereas it is easy to gather information on tumor behavior in dogs and humans where thousands of cases can be studied over time.

Despite this uncertainty, we are very hopeful that Gao Gao’s tumor will behave more like a seminoma in dogs. In 1997, a seminoma was found in 26-year-old giant panda Hsing Hsing, from the National Zoo, and treated by surgical removal. Hsing Hsing died two years later from kidney disease, and there was no evidence of any remaining tumor at his necropsy. We have had an opportunity to compare the microscopic sections of Hsing Hsing’s tumor with the samples from Gao Gao, and they are very similar.

Allan Pessier, D.V.M., Diplomate, A.C.V.P., is a senior scientist (veterinary pathologist) for the San Diego Zoo Institute for Conservation Research. Read his previous post, The Last Ones?

Update May 23, 2014: Gao Gao seems to be enjoying his keepers’ attention in his bedroom suite as he continues his recovery. He has even been soliciting neck scratches from them.

2

Beware of Crunchy Figs!

Here's a Moreton Bay fig fruit sliced in half.

The fruit of a Ficus sansibarica provides a cozy home for fig wasps.

Recently, the Wildlife Disease Laboratories received an interesting request from Seth Menser, a senior horticulturist at the San Diego Zoo, asking if we could take pictures of plant parts under the microscope. “I would really like to do a couple of shots of a fig cut in half with the fig wasps still inside. I have the figs needed for the shots. And, if you have never seen inside a fig, with the fig wasps, it is a very incredible thing to look at!” We were curious, so agreed to help.

Fig wasp

This amazing view of a fig wasp was taken in our Wildlife Disease Laboratories.

Seth brought up several figs from a Ficus macrophylla, commonly known as a Moreton Bay fig. These trees originate in the subtropical rain forest of eastern Australia but do well in frost-free climates such as ours. These majestic trees can reach up to 200 feet (60 meters) with long, aerial roots providing the tree with additional support to hold up the immense canopy. Seth brought several figs ranging from green and firm to dark maroon with spots on the outside. He explained the life cycle of the fig and the fig wasp as he cut them in half, and we set up the cameras.

Here's one

This female fig wasp has her wings. Is she ready to fly to a new fig?

Ficus trees are unique because the flowering parts of the plants are inside the fruiting parts (figs), making it difficult for insects to pollinate the trees. Thus begins the cooperative relationship with the fig wasp. The fig provides refuge and a food source for the wasps, and, in turn, the wasps pollinate the tree.

To begin the cycle, a tiny female fig wasp enters into a narrow opening (ostiloe) at one end of the fig. While wiggling into this small hole, she often looses a wing or antenna. Safely inside, she lays her eggs. As she is wandering through the fig, she spreads pollen from the fig she hatched in, thus helping the fig tree produce viable seeds. The cycle of the female wasp is complete, and she dies. Her eggs hatch, and the young wasps grow, finding food and refuge in the fig. Interestingly, only female wasps grow wings and leave the fig. The males live their entire life in the fig. Their function is to mate with the females and chew small openings through the fig’s wall for the females to escape, and the cycle begins again.

How many fig wasps can you find in this fig?

How many fig wasps can you find in this fig?

We were totally fascinated by the story. Using a dissecting scope with a camera attachment and a macro lens on a photo stand, we were able to capture the intertwined life cycles of the fig and the wasp. We photographed the narrow ostiole of the immature smooth fig where the female enters. Mature figs looked completely different on the inside. They were soft and fleshy, with delicate flower structures and seeds lightly attached to the inner walls. Each mature fig contained several wingless male wasps, and Seth was lucky enough to find one female flighted wasp.

At first glance, theses tiny wasps are difficult to see. The magnification helps, but a keen eye is needed to see them. How many can you find?

April Gorow is a senior pathology technician with the San Diego Zoo Institute for Conservation Research. Read her previous post, We Never Stop Learning.

3

We Never Stop Learning

Did you know that hedgehogs evolved 50 million years ago in San Diego County?

Did you know that hedgehogs evolved 50 million years ago in San Diego County?

Dioramas, specimen jars, and stacks of books are all images that come to mind when you think of natural history museums. Museums are not just filled with primary school students on field trips but with invaluable collections. Museum curators are not just librarians cataloging their specimens but scientists and researchers helping to save species. With the number of endangered species increasing, museums have evolved into a major resource for biologists and other researchers who study genetics, taxonomy, comparative anatomy, and even behavior.

Field biologists need to understand the animals they study. They need to understand each animal’s living requirements (food, water, space, territory, and reproductive strategies), but also anatomy and physiology. It is important to understand what makes an animal jump, fly, and live without water for long periods of time. So off to the museum they go.

We have established how important museums are, but where does the museum get their specimens? One place is from us. San Diego Zoo Global has an immense and diverse collection exceeding 7,500 animals. Many of these animals are not displayed anywhere else in the US, which makes the collection unique not only to visitors but to museums and researchers. After an extensive necropsy and investigation of an animal’s death, the body may be saved for a museum.

One of the museums we work with is our neighbor, the San Diego Natural History Museum. Phillip Unitt, the museum’s curator of birds and mammals, boasts that “donations from the San Diego Zoo’s Wildlife Disease Labs have given our collection a worldwide dimension it would otherwise not have.”
Phil likes to share the story of hedgehogs during museum collection tours. Hedgehogs were evolving 50 million years ago in San Diego County. Though now extinct in North America, paleontologists at the museum are able to compare the local fossilized remains to the African hedgehog carcasses received from the San Diego Zoo.

Animals are amazing in their diversity, anatomy, physiology, and adaptability. We continue to learn about them even after death. Archiving and sharing tissue samples from them provide rare and extremely valuable resources for current disease investigations and future research.

April Gorow is a research coordinator for the Wildlife Disease Laboratories, San Diego Zoo Institute for Conservation Research. Read her previous post, Victor Lives On.

1

Desert Tortoises: Healthy Expressions

This desert tortoise is on the thin side.

This desert tortoise is on the thin side.

Compared to the numerous mammalian species you normally encounter, such as dogs and cats, desert tortoises have relatively limited means of expression. To make matters worse, they hide out in their burrows for extended periods of time and are mostly quiet. Furthermore, they can pull their legs and head back into their shell as a safety precaution when startled, so all that remains visible are their shell and the armor-like aspects of their front and hind limb scales. So, how we can tell if a tortoise is sick?

When your physician does an exam, simply asking you questions makes the task much more straightforward. Wildlife veterinarians, on the other hand, have to be much more clever and creative in using indirect measures of health. Some steps included in a routine desert tortoise health check are:

1) Activity
Is the tortoise behaving as expected? Is it alert to its surroundings? A tortoise that is letting its head hang and does not react to the examiner may be suffering from general debilitation

2) Measurements
The tortoise’s size is determined based on its shell length, using calipers. The size is an indicator of the age group of a tortoise. All desert tortoises over 20 centimeters (about 7.9 inches) are categorized as adults. It is difficult to determine the actual age of a tortoise unless you know the hatch date. The rings on the scutes of the shell are a poor indicator of age. A regular-size adult desert tortoise weighs about 5.5 to 8.8 pounds (2.5 to 4 kilograms).

3) Body condition score
This is an indicator to determine the muscle and fat mass of a tortoise. A desert tortoise with a prominent bony ridge on the top of its head is severely under condition, whereas one that cannot retract its head and limbs into its shell due to abundant subcutaneous fat stores is well over condition.

4) Shell
The shell of a tortoise is a specialized modification of skin. It contains nerves, blood vessels, and bone and is sensitive to trauma as well as metabolic derangements. The latter can be caused by an unbalanced diet and/or lack of natural sunlight or imitations thereof leading to soft and/or malformed shells.

5) Nares
The nares are inspected for exudate (runny nose) and erosions. Depending on the type and severity of the exudate, the tortoise may be suffering from an upper respiratory tract disease. Erosion around the nares indicates a more chronic disease process

6) Oral cavity
The mucous membranes of the oral cavity are examined for a healthy pink color, and the tongue is examined for presence of erosions and/or plaques. Tortoises with yellow, casseous plaques on their tongue may be suffering from a viral or bacterial infection.

7) Coelomic cavity palpation
By carefully pressing fingers into the soft skin area near the hind legs and into the shell cavity, an experienced examiner can determine whether there are masses in the coelomic cavity. Masses may include eggs or urinary bladder stones.

Why don’t we take their temperature? Tortoises, as other reptiles, are ectotherms: they do not control their body temperature as consistently as mammals but rely on environmental sources to regulate internal heating and cooling.

Identifying unhealthy tortoises is an important task at the San Diego Zoo’s Desert Tortoise Conservation Center in Las Vegas for individual animal and population health. The Center temporarily houses almost 2,000 tortoises, and each individual has to have a health check at least once a year. The goal is to release the tortoises into their native habitat, the Mojave Desert, to increase the wild population numbers. However, only healthy animals can be released to increase their chance of survival and minimize the risk of spreading disease. Unhealthy individuals are treated by San Diego Zoo Global veterinary medical staff.

Josephine Braun, D.V.M., is a scientist in San Diego Zoo Global’s Wildlife Disease Laboratories.

1

The Social Network…of Birds

Two bee-eaters appear to be sharing a meal in their aviary.

These two bee-eaters sharing a meal in their aviary are part of the same social network.

The age of social networking has the world communicating through cyberspace on just about anything. We are now connected to a network of people on Facebook and Twitter with whom we tune in daily to see what our friends are up to. In the past hour, my friends on Facebook looked at the nutrition facts on a candy bar (Is that really a good idea?), posted a CUTE photo of a clouded leopard (thanks to my “friend,” San Diego Zoo Global), and humorously referenced her boss mistaking a Kanye West song for the ‘80s hit single “Ghostbusters.” This is my social network.

Scientists are developing new methods to understand how people are influenced by their social network. Who we are connected to in the virtual world and in real life influences different aspects of our own lives, such as whether we vote in elections, our happiness, our weight, and whether we catch the flu or acquire other diseases. In collaboration with James Fowler, Ph.D., a professor at the University of California, San Diego, we are also trying to learn how connectedness influences the spread of disease in bird populations.

Avian mycobacteriosis is a bacterial disease of birds caused by Mycobacterium avium and other related species of mycobacteria. This is a challenging disease of birds, because whenever a case arises, we do not know how far an infection has spread through a group of “connected” birds sharing the same aviary. Traditionally, disease acquisition has been attributed entirely to contact with other infected birds; however, recent studies conducted by the Wildlife Disease Laboratories, a division of the San Diego Zoo Institute for Conservation Research, show that the environment may also be playing an important role in the spread of this disease. So, which is more important, the social network or the environment?

A powerful method of untangling this dizzying question is a social network analysis. Years of careful record keeping has created an archive of data documenting each bird’s aviary and enclosure-mates. These data can be used in conjunction with health history to determine whether the occasional cases of avian mycobacteriosis we see are attributed to a bird’s social network or its environment history. What makes the problem interesting is that the network is dynamic. Similar to how I might change my Facebook network by adding or dropping a friend, one of our birds might change social networks when she moves into a new enclosure to be closer to her new boyfriend (i.e., she drops her old bird “friends” and adds a new bird “friend”). Evaluating these dynamics through time is where social network analysis is remarkably powerful. Ultimately, we hope to uncover the relative contribution of mycobacterial infections due to both the social network and the environment.

We are just beginning this fascinating journey into understanding the influence of social networks on disease dynamics in our animals, so you will have to stay tuned to find out the answers. These answers will allow us to develop better disease-management protocols to mitigate risk to birds at the San Diego Zoo and San Diego Zoo Safari Park, as well as in conservation programs around the world.

Carmel Witte is a researcher with the San Diego Zoo Institute for Conservation Research. Read her previous post, Cutting-edge Science in Historical Surroundings.

5

Blue-chinned Sapphire Mystery

Males have the bright blue plummage, while females are less striking.

Males have the bright blue plumage, while females are a bit less striking. Photo credit: Philipp Lehmann

I love watching hummingbirds in my yard. These tiny nectar-eaters amaze me with their feathers of iridescent hues. The blue-chinned sapphire Chlorostilbon notatus is a species of hummingbird covered in shiny blue feathers—more a trick of the light than an actual feather pigment. Here at the San Diego Zoo, I have been able to take an up-close look at this species, aptly named for its beautiful color. However, I am not a bird keeper, I am a pathology technician. And this bird was not on exhibit—it was in my hand as I conducted an external postmortem (after death) exam. This tiny bird, still sparkling in blue feathers, had passed away and it is my job to help determine why.

Blue-chinned sapphires were added to the Zoo’s collection from the Caribbean last year. Unfortunately, when some of them arrived they did not survive very long. My job as a pathology technician is to look for anything wrong outside and inside these animals. But I could find nothing out of the ordinary—all of its internal organs looked great.

But when our veterinary pathologists looked under the microscope at the tissues from the birds, they made a Eureka! discovery—the birds were deficient in vitamin A. The pathologists let the nutritionists know, and they tested the nectar the sapphires were being fed—it, too, was low in vitamin A! The nectar was changed, and the rest of the birds have thrived.

It might seem a ghoulish job to study animal organs, but the results are worth it. The next time you are visiting the Zoo or Safari Park, remember that, even in death, animals are helping us learn about and conserve species around the world!

Rachael Holland is a research technician at the San Diego Zoo Institute for Conservation Research’s Wildlife Disease Laboratories.

0

Veterinarians Don’t Just Operate, They Educate!

Yes, veterinarians even examine panda cubs!

Yes, veterinarians even examine panda cubs!

For veterinarians at San Diego Zoo Global, in addition to caring for the animals in our collection, one of the most important things they do is share their vast knowledge and expertise with aspiring veterinary students at the university level. Until one has actually observed or practiced in a zoo veterinary hospital, it is impossible to fully understand the amount of discipline needed and the challenges faced by veterinarians and support staff. The clinical veterinary medicine and veterinary pathology externship programs at the San Diego Zoo, San Diego Zoo Safari Park, and San Diego Zoo Institute for Conservation Research’s Wildlife Disease Laboratories provide just such an opportunity to a select group of students each year.

In 2003, our veterinarians and pathologists collaborated to create an externship program, and since then it has grown exponentially. With more than 30 accredited veterinary schools in the United States, we have collectively hosted over 200 students from the US as well as Canada, Mexico, Brazil, Germany, France, Italy, India, Thailand, and China (just to name a few!). Working with such a diverse group of students also helps us, as we gain knowledge of veterinary practices in other countries. Since we often send and receive animals to and from zoos worldwide, this proves very beneficial throughout the animal shipment process.

As with specialties in human medicine such as cardiology or orthopedics, zoo veterinary medicine is a specialty where focused training and education is required. During and even after graduation, volunteering to participate in as many observational opportunities as possible enhances students’ ability to learn the many different aspects of the profession in the clinical setting. Students should strive to observe different practice areas in veterinary medicine such as small animal, large animal, equine, zoo and exotic, pathology, research, or industrial. This demonstrates to selection committees that a student has researched the profession and holds a genuine interest in pursuing a career in the field of zoo and exotic animal medicine.

Once a veterinary student has chosen zoo medicine as a field of interest, applying for and participating in an externship rotation is an important step toward success. Most university career counseling offices have information regarding externships, and there are numerous externship opportunities listed on the American Association of Zoo Veterinarians website as well, including our facilities. Each program listing contains specific information needed for applying to select institutions. Most programs accept applications at least a year in advance, sometimes two, so it is important to begin identifying potential programs as a college freshman or sophomore.

Our veterinary student externs must be in their fourth or senior year during their rotations. This ensures they have enough experience and education to receive the greatest benefit while working in our practice. Once students graduate and obtain their degree in veterinary medicine and a license to practice, many will apply for the University of California, Davis, Residency, which includes one year each at three different zoological institutions: Sacramento Zoo, San Diego Zoo, and San Diego Zoo Safari Park. The residency program also partners with SeaWorld San Diego and offers residents an eight-week opportunity to work in aquatic veterinary medicine.

While it takes a great deal of initiative, discipline, leadership skills, and patience, working as a veterinarian in a zoo setting is also extremely rewarding. For those with sincere passion for conservation and caring for the Earth’s creatures, working as a zoo veterinarian is not just a living but truly a way of life. It brings the staff of our veterinary services and pathology departments and San Diego Zoo Global as a whole great satisfaction knowing that the years of experience we share will be translated through the work of future generations of zoo veterinarians.

For information regarding SDZG veterinary externships

For information regarding the UC Davis Residency program:
And select the following Program Descriptions:
• Zoo and Wildlife Pathology
• Zoological Medicine

Valerie Stoddard is a senior administrative assistant at the San Diego Zoo Safari Park. Read her previous post, Elephant Serenade.

5

Tortoise in the Glass: Evaluating Health Problems

To you, a typical tortoise might look like this:

desert tortoise adult

But to me, a tortoise may also look like this:

desert tortoise tissue samples

I’m a veterinary pathologist, which means I spend a lot of quality time looking through a microscope at slides with tissues to try to evaluate health problems that show up as changes in those tissues. I can find dying cells, inflammation, various pathogens, scarring, thinning, thickening, bleeding, tumors, strange crystals, and unusual pigments. All of the changes help us understand the health problems affecting an animal.

At the San Diego Zoo Institute for Conservation Research, I work exclusively on tortoises that have died at the Desert Tortoise Conservation Center. Why bother? Well, it turns out that one of the best ways to figure out what health indicators most accurately indicate disease is to compare the information from the live tortoise to the changes we see in the tissues if the animal dies. The more we know about which tools work to predict severity and type of disease, the faster and more precise we are at identifying and helping animals at risk.

To get information from enough tortoises to allow good conclusions to be drawn, I need to look at a lot of slides. Since 2009, over 4,500 slides have been made of desert tortoise tissues, providing an invaluable resource for the understanding of disease in desert tortoises. Since November 2012, I’ve been describing the changes I see so that they can be correlated to what was found in the live animal. Thankfully, I haven’t been working all alone; Dr. Lily Cheng, another veterinary pathologist, volunteered to spend two whole months staring at a mountain of desert tortoise slides. Between the two of us, we’ve done more than 3,000 slides belonging to over 250 tortoises!

Are you curious about what sorts of things we see? Good! We are always on the lookout for bacteria or viruses that cause that most feared of tortoise infections: upper respiratory disease. This is more than just a head cold like people get and is a big factor in tortoise population decline. Some savvy souls may note that no light microscope can show an individual virus particle (you really need an electron microscope for that, since viruses are smaller than the wavelength of visible light). Conveniently, however, some viruses clump together to form rafts of virus particles. These are big enough to see with a microscope, just as you can see a patch of lawn even if you are too far away to pick out a single blade of grass. The virus most common and dangerous in tortoise respiratory disease (herpesvirus) forms these aggregations in the nuclei of cells, and they are called intranuclear inclusions.

Below are some cells from a tortoise that had severe upper respiratory disease. On the left side of the picture, you can see normal nuclei: round or oval purple shapes that look very speckled, like chocolate chip cookies. On the right side of the picture, the nuclei are bigger and have clumps of magenta in the center surrounded by a clear rim. They no longer resemble chocolate chip cookies at all. Those magenta blobs are viral inclusions from herpesvirus!

Herpes inclusions

The work continues at a good pace, and there are only about 1,300 slides left to look at. They weigh almost 7 kilograms (15 pounds) altogether. Wish me luck!

Kali Holder, D.V.M., is a postdoctoral associate in the Wildlife Disease Laboratories for San Diego Zoo Global.