Wanted: Dead or Alive

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!

Diseases can often be a very scary thing we don’t know too much about, but this week at Zoo InternQuest we got an in-depth look at what diseases really are and how they work on a microscopic level.

Pictured above is our presenter Dr. Wesley Siniard (middle) and two students visiting from UC Davis’ School of Veterinary Medicine. Dr. Siniard is a resident pathologist at the San Diego Zoo’s animal hospital. Pathology a type of science that focuses on the causes and effects of diseases. Specifically, Dr. Siniard is a Veterinary Pathologist which means she studies diseases or tissue abnormalities found in domestic and exotic animals. There are actually two types of Veterinary Pathology, Anatomical Pathology and Clinical Pathology. Anatomical Pathology involves examining whole animals and their tissues, while Clinical Pathology focuses primarily on cells and lab work. Dr. Siniard prefers to work in Anatomical Pathology, but is involved with both branches in her everyday work at the Zoo.


Since Dr. Siniard is in training at the San Diego Zoo her position is classified even further as a Zoological Pathologist. Zoological Pathology is an informal sub-specialty of Veterinary Pathology and focuses primarily on diseases found in non-domestic animals. The main goal of a Zoological Pathologist is to maintain the health of every animal in the collection. This is done mostly through preventative actions such as vaccinations, surgical biopsies, and research through necropsies. A necropsy is simply an autopsy performed on an animal.


A significant amount of Dr. Siniard’s time is spent analyzing samples of tissues from various animals. These samples can either be collected through a gross necropsy, or through biopsies taken during a routine medical exam. Once these samples are obtained, they are put in a bucket of formalin in order to fix or preserve the tissues. They are then placed in a small cassette and dipped into paraffin wax. In the two pictures above, you can see tissue samples that have gone through this process. Once the sample has been prepared and dyed, it is sliced very thinly and placed on a slide. After these slides are prepared by the Zoo’s Histology Department, they are passed off to Dr. Siniard for diagnostics. While examining the slides, Dr. Siniard is looking at the present cell types in order to detect possible infectious agents, and evaluate the general state of the tissue. This helps to diagnose abnormalities and determine a future course of action.


If Dr. Siniard finds an abnormality, such as the intestinal worms pictured above, she would inform the individuals who care for that animal or any animals that came in contact with it. This is done in an effort to prevent the spread of a contagious disease. Obviously, in this case, the abnormality is not contagious but it is always better to be safe than sorry! Dr. Siniard and other employees at the Hospital actually perform necropsies on every animal that is found deceased on zoo grounds. Species native to San Diego frequently make their way onto zoo grounds and occasionally pass away on site. If this situation occurs, the Zoo’s security will be contacted and the animal will be brought to the Hospital for a necropsy. This is a preventative measure and is primarily used to screen for local diseases.


Another aspect of Dr. Siniard’s job is detecting potential infections in lesions or abrasions. Pictured above is a preserved cross-section of an elephant’s foot. As you may know, elephants are fairly large animals ranging anywhere from 6,000 lbs to 13,000 lbs depending on the species. All that weight on their feet coupled with the fact that their weight majorly rests in their toes can result in quite a few physical problems, especially as they age. These often include toenail abscess or lesions in the toenail. In these situations, Ms. Siniard will receive a slide with a tissue sample to analyze for any potential abnormalities. She will then determine if the lesion is due merely to inflammation or a more devious player.


Along with lab work, Ms. Siniard frequently performs what is referred to as a gross necropsy. This is essentially a necropsy performed with the naked eye. The process starts with a standard physical exam of the outer body and leads to an examination of the internal organs and tissue. These examinations are useful for identifying significant and apparent abnormalities. Pictured above is a sample of parasite-ridden tissue found in a gazelle, this type of ailment would be easy for a pathologist to spot in a gross necropsy. Even if the pathologists believe they have identified the abnormality, they will still collect tissue samples to determine the specifics of the situation.


Pictured above is another example of an abnormality that would be spotted during a gross necropsy. It is an enterolith that was found in a red lechwe, which is a species of antelope native to Africa. An enterolith is a mineral concretion that is formed in the gastrointestinal system. The presence of an enterolith can be a clue that the animal’s diet is too concentrated with a specific mineral. When these types of mineral concentrations are found, the pathologists inform the veterinary staff and keepers in charge of its dietary needs. Veterinary Pathologists, like Dr. Siniard actually work quite closely with keepers to maintain the animals health.


Along with examining abnormalities found within an animal, employees of the Hospital will also examine the skeletal and muscular systems to gage the animals health. Pictured above are two images of an Alpine ibex’s horn. Notice the dark spot located near the top of horn, this is they type of abnormality pathologists would be looking for during a necropsy. Horns can actually serve as a valuable tool to determine the state of an animal’s health. Like our fingernails and hair, horns are made of keratin and reflect a few aspects of their diet. If the outer appearance of the horn seems to be flakey or weak, it may be time to adjust their diet and care to better fit a nutritional need.


The pathologists at the San Diego Zoo are essential members of the organization and play a huge role in keeping our animals in tip-top shape. Not only do pathologists, like Dr. Siniard, diagnose abnormalities post-mortem, they also aid keepers and veterinary staff in the care of the animals.

Helena, Photo Team
Week Four, Fall Session 2018

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