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wildlife disease laboratories

2

Tortoise in the Glass: Evaluating Health Problems

By
Kali Holder
– April 15, 2013Posted in: Animals and Plants, Animals site sub feature, Conservation, Conservation at the Zoo, Desert Tortoises, Reptiles and Amphibians, Uncategorized

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.

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1

Cutting-edge Science in Historical Surroundings

By
Carmel Witte
– November 16, 2012Posted in: Conservation, Conservation at the Zoo, Uncategorized

Looking across St. Michael’s bridge, early morning, in Ghent, Belgium.

I stood on the side of Saint Michael’s bridge staring at the stunning city before me: Ghent, Belgium. For four nights I was privileged to live in the beauty of this Central European city and take in all of her cafes, castles, and (my favorite!) chocolate. More importantly, I was there on official San Diego Zoo Global business to join some of the world’s best minds for a short, intensive workshop on molecular epidemiology and attend an influential conference that is held only once every three years: The International Symposium of Veterinary Epidemiology and Economics (ISVEE; endearingly called “iz-v”). It was an amazing opportunity provided by special funds set aside for employee development to meet with, learn from, and establish collaborations with some of the best in the field.

My journey started with the workshop in molecular epidemiology. The course instructors came from distant corners of the globe, including New Zealand, Scotland, and the U.S. to share their expertise with approximately 30 participants. We gathered for 3 days under the dim lights and a vaulted ceiling of wooden beams on the 4th floor (a.k.a. the attic) of a medieval Dominican monastery, Het Pand. This venue was not exactly the white, sterile laboratory from the movies (or the Zoo’s lab!) in which molecular science is usually performed, but I liked the contrast…cutting-edge science in historical surroundings.

Het Pand is the medieval Dominican Monastery where the molecular epidemiology course was held, Ghent, Belgium.

Molecular epidemiology is a specialized subfield of epidemiology (see Epidemi-what?) that requires unique tools and techniques to uncover patterns of disease transmission at the genetic level. My interest in this topic stems from the Zoo’s Molecular Diagnostic Laboratory. The lab was established in 1999 as part of the Wildlife Disease Laboratories to fulfill a need to develop diagnostic tests suitable for our animals and to improve our ability to identify and control important diseases. As one of the only zoo-based molecular diagnostic labs in the world, it has been instrumental in the development of diagnostic tests and animal disease research. For example, in 2007 a generous grant from the Ellen Browning Scripps Foundation allowed us to carry out a large study to describe herpesviruses in hoofed mammals (antelope, deer, goats, sheep, cows, and similar species). These herpesviruses can cause a fatal disease called malignant catarrhal fever when they are passed from animals that naturally carry the virus to new, susceptible hosts. Molecular methods can be used to look at the genetic similarities between viruses found in different animals to determine who is passing them to whom. This is where the epidemiology comes in.

Looking for patterns within molecular data (i.e., patterns across changes in DNA) requires methods that are new to me as an analytical epidemiologist. Thus, my goal in attending the course was to develop a working knowledge of such techniques to further improve the Wildlife Disease Laboratories’ ability to answer some pressing conservation questions. On the second day I was introduced to a new data analysis technique called Analysis of Molecular Variance (or “AMOVA” for short). Such a technique will allow me to extend our valuable data on herpesviruses and ask new or additional questions like: “Are animals in multispecies exhibits more likely to transmit the virus to each other?” Such an analysis could have a big impact on providing information that helps zoos better manage endangered species in the presence of this known disease.

A view of Maastricht, looking over the Meuse river.

Following the workshop, my travels then took me 90 miles east to the Belgium-Netherlands border where I joined 1,000 conference participants in Maastricht, The Netherlands, for 5 days of everything-animal-related epidemiology. Maastricht is a beautiful, historic-yet-modern city on the banks of the Meuse River that is famous for the birthplace of the European Union and the single European currency, the euro. My days in Maastricht consisted of attending talks on the latest work in the field, while the evenings presented opportunities to meet veterinary epidemiologists from around the world and engage in discussions of their research projects and areas of expertise.

I was honored to be a representative of San Diego Zoo Global at this venue and share some of our notable conservation work in epidemiology. Experiences like these provide me with better capabilities for using science to save species.

Carmel Witte is a senior research coordinator at the San Diego Zoo Institute for Conservation Research. Read her previous post, Investigating Primate Malaria in the Amazon.

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5

Investigating Primate Malaria in the Amazon

By
Carmel Witte
– September 17, 2012Posted in: Animals and Plants, Apes and Monkeys, Conservation, Conservation at the Zoo, Projects in the Field, Uncategorized

A microscope slide shows the malarial parasite in a red blood cell red (see arrow) of a sampled primate.

When I first met Marina Bueno, I was instantly drawn to her excitement and passion for research in conservation medicine, a field that blends aspects of wildlife conservation, wildlife health, and human health. Marina is a veterinarian and doctorate scientist who works with the University of São Paulo’s Laboratory of Wildlife Comparative Pathology in the School of Veterinary Medicine and Animal Sciences. She also works with TRÍADE, a Brazilian organization for conservation medicine research, and Instituto Pri-Matas, a nonprofit organization conducting a project with golden-headed lion tamarins. Last summer, Marina spent extended time training in our Molecular Diagnostics Lab, learning how to improve DNA isolation techniques for some of her work. This is where we first discussed potential opportunities for collaboration on her projects investigating primate malaria in the Amazon.

Brazil’s Amazon region is seeing large-scale, human-induced (often referred to as anthropogenic) environmental changes that affect people and wildlife habitat. In a study conducted by Marina and collaborators, primates were surveyed across two protected field sites in the Amazon that are currently under severe anthropogenic pressure due to large construction projects that include the building of roads and dams. The idea was to sample South American primates in these sites to better understand what diseases they have and how these diseases could impact primate conservation and human health in these areas.

Marina Bueno samples primates in the Amazon for potential diseases.

They found that approximately 20 percent of surveyed primates carried a malaria-causing parasite, Plasmodium brasilianum. While infection with primate malaria generally does not harm the primates, there has been speculation that some of the primate-specific malarial parasites may not be so primate-specific. Some scientists believe that mosquitoes feeding on primates infected with Plasmodium brasilianumcould transmit the malarial parasite to humans when they bite a human host.

Marina’s research documents these malaria infections in primates, providing recommendations to closely monitor the human and primate populations for Plasmodium brasilianum infection in these areas of severe anthropogenic pressure, a situation that has been known to promote human malaria epidemics. The investigation also recommends that primates be tested for the presence of malaria infection before being relocated to other areas of Brazil for conservation or translocation projects so as not to inadvertently introduce malaria into areas where it has been eradicated.

Working collaboratively with scientists from around the world is a role that our Wildlife Disease Laboratories naturally falls into with its multidisciplinary group that includes veterinary pathologists, scientists, a molecular diagnostic laboratory, a histology laboratory, and an epidemiologist. Epidemiology expertise was provided for this particular collaborative project on primate malaria in the Amazon region. The study will be published soon in a peer-reviewed journal.

We are excited about our collaborations with our Brazilian counterparts in their quest to conserve one of the most ecologically diverse areas of the world and their search for harmony between human progress and wildlife conservation.

Carmel Witte is a senior research coordinator at the San Diego Zoo Institute for Conservation Research. Read her previous post, Epidemi-what?

The above photos are printed with permission from Marina Bueno.

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4

Victor Lives On

By
Rachel Burns and April Gorow
– July 3, 2012Posted in: Animal Stories, Animals and Plants, Animals site sub feature, Conservation, Conservation at the Zoo, Uncategorized

Victor the echidna

At the end of April, the San Diego Zoo mourned the passing of probably its oldest mammal resident. He arrived here in 1956 and was believed to be more than 58 years old at the time of his death. Was he a great ape? An elephant? A rhinoceros? None of the above. Victor was a short-nosed echidna, a spiny, egg-laying mammal (called a monotreme) from Australia about the size of a large housecat. In his years in our Children’s Zoo, Victor touched (or at least was touched by!) thousands of visitors fascinated by this unusual and amazing creature. His death may have ended his long career as an animal ambassador, but even after death, Victor continues to be a source of important information and learning.

Part of our job in the Wildlife Disease Laboratories is to help ensure the health and well-being of the animals in our care. But no matter how well we do our job, all animals eventually reach the end of their natural lifespan, be it 6 years or 60. When this happens, we try to make the most of a difficult situation by turning it into an opportunity to share and to learn. What we learn from our animals after they die is very important and helps our living collection. We are keeping the live animals alive by learning from them after they pass away. Learning and sharing knowledge is a key role we play in the circle of life.

Thousands of Zoo visitors met Victor up close during his time with us.

When Victor died, his body came to us. We performed the animal version of an autopsy, called a necropsy, to look for disease and determine his cause of death. How do we do this? Well, if you’ve seen an episode of CSI or Bones, you probably have some idea, but the lesions of natural disease are different, and recognizing them depends first and foremost on knowing what is normal. As you can imagine, in our line of work, with the large diversity of animals we see, “normal” is relative! With their narrow, toothless beaks, lack of external ear flaps, internal testicles, and single opening for urogenital and digestive tracts (called a cloaca), normal for an echidna is certainly abnormal for most other mammals. In fact, it sounds more like a bird!

Never having seen the inside of an echidna, we relied on knowledge of the species, published information, and years of experience with other animals to separate abnormalities related to disease from normal anatomy. Luckily for us, there are generally more similarities than differences, and a disease in one species often looks the same in another. Ultimately, Victor’s problem, like many older primates and dogs, was his heart. A large, dilated heart with white streaks of scar tissue in its muscle points to heart disease in any animal. Victor had been undergoing treatment for heart failure when he died, and the necropsy findings confirmed the clinical diagnosis.

While this information about one animal might not seem like much, over time, with thorough documentation, knowledge of the common diseases in echidnas will help zoos screen their animals for these diseases and initiate treatment earlier. Tissues preserved from Victor on glass slides are now part of a museum-quality archive that can be used for future studies. Additional tissue samples went to other research divisions at the San Diego Zoo Institute for Conservation Research, where these precious specimens could provide important insights in the fields of genetics and reproductive physiology. His body was donated to a museum to be a source of learning and enjoyment for future generations.

Our collections are a finite and irreplaceable treasure of biodiversity, which is why we collect, conserve, and share biomaterials in support of nonprofit research that furthers our conservation and education mission. In this way, Victor lives on!

April Gorow is a research coordinator and Rachel Burns is the Steel Endowed Pathology Fellow, Wildlife Disease Laboratories, San Diego Zoo Institute for Conservation Research.

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6

Epidemi-what?

By
Carmel Witte
– July 2, 2012Posted in: Animals and Plants, Birds, Conservation, Conservation at the Zoo, Uncategorized

Micronesian kingfishers are highly endangered and seemingly quite susceptible to the avian mycobacteriosis disease.

Whenever I am asked “What do you do for a profession?,” I am often confronted with a familiar, perplexing look followed by a request for clarification: “Epidemi-what?” Epidemiologist. The first thing that seems to enter people’s minds is “epidermis,” the top layer of skin. But, no, I don’t study skin. An epidemiologist studies causes and patterns of disease and health in populations (think epidemic). But what does that really mean, and what role does this funny word play in wildlife conservation?

The field of epidemiology has its roots in human health and is something that most of us are exposed to every day. All of those health-related statistics (such as the ones that say that if you have high cholesterol, then you are more likely to develop heart disease) are generated by epidemiologists. Basically, the epidemiologists look for differences in frequencies of heart disease between groups that do and do not have high cholesterol. As you can guess there are probably a lot of other things that could affect whether someone develops heart disease. The art of epidemiology is dealing with those “other” things through the use of special scientific study designs and analytical techniques. Instead of people and heart disease, my subjects are animals and their health issues.

Epidemiologist Carmel Witte studies causes and patterns of disease and health in zoo animal populations.

One of my first projects was investigating avian mycobacteriosis. This bacterial bird disease has long been thought of as highly contagious: if one bird in an aviary acquires the disease, the fear is that it will quickly spread to all of the other birds. The management implications are significant, causing a halt to breeding of all endangered species living in entire aviaries. So, we decided to ask the simple question, “Is this disease really super-contagious?”

I began tackling this question by using archived animal health data generated by San Diego Zoo Global’s pathologists and veterinarians. I searched records from the past 20 years to identify all of the cases of mycobacteriosis that we ever had. Then, I analyzed thousands of bird records to see what kinds of exposure all of the collection birds had to the relatively small group of 79 infected birds. What I found was rather interesting: up to 96 percent of all birds coming into contact with a disease-carrying bird never developed mycobacteriosis. The conservation implications for this are big: it is likely that mycobacteriois isn’t super-contagious, and zoos probably don’t need to halt breeding when a case is diagnosed.

This avian mycobacteriosis project is just one of many that I continue to tackle with the Wildlife Disease Laboratories’ team. Some other projects include studying feline herpesvirus infections in cheetahs and investigating transmission patterns of herpesviruses and mycobacterial infections in hoofed animals. In all of these projects, my mission is to use epidemiology to help remove disease as a roadblock to conservation and solve pressing health problems in animals. Now that you know exactly what a zoo epidemiologist does, the next time you hear that funny word, you will have the privilege of bypassing the “Epidemi-what?”!

Carmel Witte is a senior research coordinator at the San Diego Zoo Institute for Conservation Research.

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3

Parasites in a Pelican

By
Rachel Burns
– May 29, 2012Posted in: Animal Stories, Animals and Plants, Birds, Conservation, Conservation at the Zoo, Uncategorized

American white pelicans fly in for a visit to the Safari Park.

We see the really weird stuff here in the Wildlife Disease Laboratories, and that’s why I love my job! As a pathologist, my role is to diagnose disease in our animals and, if possible, figure out its cause so that it can be treated or prevented. On animals that die, we perform a necropsy (the animal equivalent of a human autopsy) to determine the cause of death and monitor the health of the collection. Certain diseases can have serious implications for the individual animals or even for the species as a whole, since so many of the animals we work with are endangered.

But our collection animals are not the only ones we screen for disease. We also examine all wildlife that dies on our grounds, as these animals can act as sentinels for threats to native species as well as to our exotic animals or even to people. Sometimes, however, a disease entity turns up that is so new it presents more questions than answers. Such was a case I had not too long ago that started with a call from Megan Varney, one of our pathology technicians. “You’ve got to see this pelican’s liver!” she says.

The bird was a wild, young female American white pelican that was found dead at the San Diego Zoo Safari Park that morning. This native species with its characteristic pouch can often be seen visiting and enjoying the lakes at the Park. With their big, yellow bills, all-white plumage, and large wingspan (second only to the California condor among North American birds), they are hard to miss! I dash to the necropsy room to see what Megan has found in this one. For a pathologist, it is a truly spectacular sight. The liver, normally a solid brown, is swollen and riddled with yellow spots, not just on its surface but on the inside, too (see cross-section at left), and the spleen has a similar appearance.

Yikes! It looks like something has caused large numbers of cells in the liver and spleen to die, creating the yellow lesions. But what? I run through a list of possible causes in my head, but I have a feeling that this could be something new. To the microscope! Sure enough, looking at slides made from thin sections of liver tissue under the microscope, I can see infectious organisms in the lesions. They appear as pale-purple blobs mixed with the dead pink liver cells.

It is a single-celled organism, a protozoan parasite, but not one with which I am familiar. Thankfully, I am not alone—even our parasitology consultant is stumped! I send tissue to our Molecular Diagnostics Laboratory, which can isolate the DNA of this mystery organism by PCR and, we hope, get it identified. Samples of tissue are also sent out to be looked at with an even bigger microscope, an electron microscope. The results of these additional tests agree: the parasite is a flagellate called Tetratrichomonas. Although known to be a parasite of ducks and geese, it has rarely been seen to cause disease, and certainly not in a pelican.

So what does this mean for the other animals at the Safari Park? Thankfully, it appears not much. Several months have passed with no new cases, and this unlucky pelican might turn out to be the only case we ever see. Many questions remain unanswered, though: Why this bird? Where did she get the infection? And what else might be susceptible? We are continuing to investigate these questions and more by working to better characterize this organism. Perhaps we’ve discovered a new strain or species! In the meantime, I will also present this information at a national zoo and wildlife pathology workshop to make others aware. And now that we know what it is, we are on the lookout with heightened surveillance so that we can be prepared for whatever happens next. In this job, it really is something new every day!

Rachel Burns is the Steel Endowed Pathology Fellow, Wildlife Disease Laboratories, San Diego Zoo Institute for Conservation Research.

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4

Breeding Snow Leopards: Lab View

By
Barbara Durrant
– May 23, 2012Posted in: Animal Stories, Animals and Plants, Cats, Conservation, Conservation at the Zoo, Uncategorized

Does Beau have what it takes?

Last month, Mammal Keeper Todd Speis blogged about the introduction and subsequent breeding of Anna, the Zoo’s snow leopard, and her new mate, Beau (see Snow Leopards: Love at Second Sight?). Our Reproductive Physiology Department staff first met Beau in 2006 at his previous home in the Santa Barbara Zoo. We were there to perform a semen collection procedure to assess his potential fertility, not knowing at the time that one day he would come to the San Diego Zoo. Beau was a gorgeous snow leopard with motile sperm.

Back in San Diego, Anna and her long-time mate, Everett, were a compatible breeding pair, but despite their efforts she never became pregnant. We were asked to examine the pair to try to diagnose the problem and offer a possible solution. The first, and least invasive step, was to analyze Anna’s estrous cycles. Keepers collected fecal samples, froze them, and sent them to our Endocrine Laboratory, where Alan Fetter charted her cycles by measuring her fecal estrogen and progesterone levels.

We could see that she was breeding at the appropriate time in her cycle, and she was ovulating normally. When her progesterone remained elevated after each of two breeding cycles, we were hopeful that she was pregnant. But each time her progesterone plummeted back to baseline within two months, indicating that she had experienced a pseudopregnancy (also known as a false pregnancy). This condition is not uncommon among mammals, especially in carnivores. In most cases, pseudopregnancies last half to two-thirds of the length of a normal pregnancy, which is what we observed with Anna. A pseudopregnancy occurs when a female ovulates but does not conceive. For a few weeks her body produces hormones to support a pregnancy even though there is no embryo present. Eventually, with no communication from an embryo, the female’s body returns to normal, and she cycles again.

After two documented pseudopregnancies, it was time to take the next step by examining Everett’s sperm. Three semen collection procedures from 2008 to 2011 yielded samples completely devoid of sperm! During the last collection, the veterinary staff collected tissue biopsies from each of Everett’s testicles and sent them to our Wildlife Disease Laboratories pathology group. After careful assessment of the tissue, the disappointing report and photos clearly indicated that Everett was not manufacturing sperm. The reason for his inability to produce gametes was unknown, but his infertility was now an indisputable fact.

Curators at both zoos arranged an exchange between San Diego and Santa Barbara, and Beau moved south to our Zoo. As Todd described, Beau and Anna took a little time to get to know each other but then began to breed. We were excited to assay Anna’s samples to see if the new pair would be successful. Following breeding in January of this year, Anna’s progesterone rose significantly, indicating that she had ovulated. Our hopes for a pregnancy, though, were again dashed when two months later her progesterone dropped back down to baseline.

But there was a very encouraging difference in this pseudopregnancy. This time Anna’s estrogen levels were twice as high as in previous pseudopregnancies and remained high for nearly one month in contrast to the rapid decline seen before. We are hopeful that very soon Anna will experience a normal pregnancy and have the opportunity to raise a litter of cubs. We’ll be watching from the lab.

Barbara Durrant is the Henshaw Director of Reproductive Physiology at the San Diego Zoo Institute for Conservation Research. Read her previous post, Meeting Hua Mei’s Son.

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1

The Last Ones?

By
Allan Pessier
– May 15, 2012Posted in: Animal Stories, Animals and Plants, Conservation, Conservation at the Zoo, Projects in the Field, Reptiles and Amphibians, Uncategorized

Panamanian golden frog

If you sat next to me on the plane traveling home from Panama this past February, you probably thought that my tote bag was full of souvenirs from a grand, tropical vacation. Instead, I was carrying the carefully preserved and packaged bodies of endangered frogs from captive survival-assurance populations. This was a trip that required months of careful planning and lots of red tape in obtaining and using the complicated permits needed to transport wildlife samples. Far from being morbid, icky, or gross, these specimens were extremely valuable for scientific efforts to save amphibian species from extinction. So why would anyone willingly travel with dead frogs?

Does Allan's yellow tote bag hold hope for amphibian species?

To explain, I should tell you that I’m a veterinarian who specializes in pathology. Therefore, my day-to-day responsibilities are focused on using laboratory techniques, including necropsies (animal autopsies), to accurately diagnose disease in animals at the San Diego Zoo and the San Diego Zoo Safari Park as well as our field conservation programs. Through these activities, our Wildlife Disease Laboratories have a mission to remove disease as a roadblock to wildlife conservation. By bringing these deceased frogs to our laboratory and sleuthing out their parasites and disease problems, we hope to make useful recommendations that can help improve things like animal diets or aid veterinarians in selecting the very best treatments. Ultimately, this helps to ensure that the captive populations can be sustained and thrive until they can someday return to the wild.

Promoting the success of amphibian survival assurance populations is no trivial matter: more than one third of the world’s approximately 6,000 amphibian species are in decline because of introduced disease, loss of habitat, environmental change, and human exploitation. Although sometimes I get wrapped up in dry scientific and technical details, this group of frogs from Panama now in my bag really reminded me of why I do what I do.

Allan holds some of the carefully preserved frog specimens for study.

Among these specimens were species like the Panamanian golden frog, which soon may survive only in captive survival assurance populations, and the fringe-limbed tree frog, for which only a single individual is still known to exist. It is difficult to describe the feeling of holding what may be the last individuals of an entire species in your hand, but I can tell you that it hit hard for me, and I know that it is worse for friends and colleagues on the front lines of the amphibian decline who don’t have the luxury of retreating into the laboratory.

I am privileged to work for a unique organization that recognizes the importance of what might seem like an unusual scholarly activity. Collaborating with colleagues nationally and internationally really makes amphibian conservation happen! I also have the support of an amazing team in the Wildlife Disease Laboratories who will move mountains if they think it will help animals in need.

If you’d like to know more about the amphibian extinction crisis and what you can do to help, please visit the Amphibian Ark® online at www.amphibianark.org. Some of the most important actions for saving amphibian species, like protecting the environment and raising awareness of the plight of animals, can happen from within our homes.

Allan Pessier is a senior scientist for the Wildlife Disease Laboratories, San Diego Zoo Institute for Conservation Research.

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12

Found: Strange Things in Animal Exhibits

By
Bruce Rideout
– May 14, 2012Posted in: Animals and Plants, Apes and Monkeys, Conservation, Conservation at the Zoo, Uncategorized

A lion-tailed macaque

One of the fun things about working in a zoo is that each day brings something new and different; we never know what we will be working on from one day to the next. Most of our work in the Wildlife Disease Laboratories, San Diego Zoo Institute for Conservation Research, involves examining animal tissues and fluids for disease surveillance, diagnostics, and research designed to improve the health and well-being of the animals in our care. But every once in a while we have to solve a mystery about strange things found in our animal exhibits. Animal keepers are very vigilant in monitoring their animals and exhibit environments. If some unidentified thing found in an exhibit might be an indication of a disease problem in an animal, or a health threat to an animal, it is our job to identify the object and determine its significance.

This is what a normal primate placenta looks like under the microscope.

Some time ago we had a five-year-old, pregnant lion-tailed macaque at the Zoo that had been a good mother to her previous two offspring; this time she delivered an infant that was found cold and weak shortly after birth. The veterinarians were concerned that this might be evidence of an infection in the baby, and possibly the mother as well. One of the best ways to diagnose a neonatal infection is to examine the placenta, so the keeper wisely set about scouring the enclosure and eventually found something that was the right color and consistency to be a piece of placenta. It was submitted to us for an urgent examination. We quickly processed it for microscopic examination and began our investigation.

The mystery tissue under the microscope.

Although the sample looked like a piece of placenta to the naked eye, it didn’t look anything like a placenta under the microscope (see photo at right). If it wasn’t a placenta, what was it?

The first thing to notice is the presence of thin pink outlines surrounding clear spaces. Within these clear spaces are translucent objects with dark centers.

When we see strange translucent structures like this, one quick evaluation tool we often turn to is examination under polarized light. Some objects transmit polarized light while others block it, which gives us information about the structural nature of the material.

The mystery tissue polarized

This photo at left shows the translucent structures illuminated with polarized light. You can see they glow pink and blue. This helps me confirm my suspicion: this is not a piece of placenta but a piece of sweet potato! The thin, pink outlines are the plant cell walls and the small translucent objects are starch granules (the things that make sweet potatoes rich in carbohydrates). Sweet potatoes are a normal part of the diet of these animals, so this sample represented a small piece of food that had been lost in the exhibit and had become desiccated just enough to make it difficult to identify.

In the end, no placenta was ever found, but the story had a happy ending, as the infant quickly recovered and was successfully reared by his mother. Although our investigation in this case took an unexpected turn and ended up not being as useful as we had hoped in guiding the immediate treatment of the infant, in other cases it does. Stay tuned for our next installment, when we reveal how you can tell whether something that looks like vomit really is. Until then, I can’t wait to see what diagnostic challenges we’ll face tomorrow.

Bruce Rideout is the director of the Wildlife Disease Laboratories, San Diego Zoo Institute for Conservation Research.

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7

Desert Tortoise CSI

By
Larisa Gokool
– August 16, 2011Posted in: Animal Stories, Animals and Plants, Conservation, Desert Tortoises, Reptiles and Amphibians, Uncategorized

"Detective" Larisa prepares for a necropsy.

The scene:
The hot, arid Mojave desert. Yuccas and Joshua trees sparsely dispersed in the foreground. Yellow “caution” tape surrounding the affected area. Photographs being snapped with numbers and rulers.

DTCC research associate:
The victim (adult male tortoise) was found lying in dorsal recumbancy (on the carapace) in front of an empty manmade burrow, urates on the plastron and ground. A fellow male and female tortoise look on from the corner of the tortoise pen.

DTCC pathology tech:
Looks like a case of love……gone wrong … YYYEEEAAAAAAHHHHH!!

Okay, okay, that’s not how my day actually plays out when a dead tortoise is found on site, which luckily isn’t too often, but we do have a pseudo-CSI department here at the San Diego Zoo’s Desert Tortoise Conservation Center (DTCC).

The tools of the trade we use in conducting our CSI activities, all set up in the necropsy trailer. The Mojave Desert can be seen through the window

If and when a tortoise is found dead on site, or needs to be humanely euthanized due to a debilitating illness or severe injury, it is immediately brought to the pathology trailer for necropsy. A necropsy is an animal autopsy, and it is performed by me, the pathology technician, as proxy for our pathologist who is based at the San Diego Zoo’s Wildlife Disease Laboratories. The necropsy helps determine the cause of death by examining body lesions or changes in tissues.

I begin a necropsy by verifying the death and identification of the tortoise, taking external measurements (weight, size, etc.), and noting any abnormalities seen on the exterior portions of the tortoise. After the external examination, I perform the internal examination, inspecting the organs, muscles, and joints, taking representative samples from each section for molecular diagnostics and histology. For histology, very thin-cut sections of these tissue samples (~10 µm thick) are mounted and stained on glass slides for microscopic examination of cells, structures, and immune response cells not visible to the naked eye. For molecular diagnostics we isolate DNA out of the tissue samples for real-time PCR, used to detect microorganisms. The samples, along with my gross descriptions (not gross as in disgusting, but gross as in overall) and photographic documentation of the case are sent to the pathologist, who will then interpret all of this information to make a diagnosis of why a tortoise died or the main cause of disease if it was euthanized.

A desert tortoise undergoing necropsy to determine the cause of death.

Necropsy is a very useful tool for maintaining the health of a captive population, especially for an animal listed as an endangered species, such as the desert tortoise. By conducting necropsies, we have the opportunity to learn from the unfortunate death of an animal on site. We can see tissue proliferations, severe inflammation, and abscesses that are not externally visible in areas such as the lungs. We also inspect changes to the nasal cavities, an area frequently affected by Mycoplasma agassizii, one of the leading causes of upper respiratory tract disease in tortoises. We can see an excess in production of mineral deposits, such as uroliths (bladder stones) within the urinary bladder that are too large for the animal to pass so they cause a blockage. We can also see endoparasites present within the GI tract that we can sample for identification.

Identifying infectious diseases and disease-causing agents is the first step toward mitigating disease in the remaining population and establishing screening tests. Thus, by investigating the deaths at the DTCC we are able to make more informed decisions regarding how to provide the best care for these animals that are destined to augment the dwindling wild populations.

Larisa Gokool is a research associate at the San Diego Zoo Desert Tortoise Conservation Center. Read her previous post, Meeting Galápagos Tortoises.

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