Meet our pathologist, Dr. Mary Duncan. She investigates animal deaths at the Saint Louis Zoo to track patterns of disease and identify problems to prevent future deaths. Here are some questions the Zoo is frequently asked:
Q. What causes the death of zoo animals?
A. Because they are carefully watched and tended in captivity, most animals in zoos outlive the expected lifespan of their wild counterparts. It's important to remember that the mortality rate among zoo animals is 100%, just as it is among all living organisms.
Complications associated with old age eventually claim many zoo animals. Heart disease and kidney failure are what are commonly found in aged animals.
Infectious diseases that overwhelm the animals' defense systems are reasons for some deaths. When zoo animals get infectious diseases that can transmitted to other animals, it is important for us to be able to identify the cause of death in these instances.
Some animals died of their diseases despite our efforts to help them. Other animals are humanely euthanized if the veterinarians, curators and keepers agree that an animal is suffering and unlikely to recover.
Q. What happens to an animal after it dies?
A. For several reasons it is important to try to identify the cause of death for every animal. This may help us determine if there are specific management problems or to discover common diseases of a group of animals or, if necessary or possible, initiate changes that might prevent other deaths from the same cause.
All animals that die at the Saint Louis Zoo, from spiny mice to elephants, receive a necropsy - the animal equivalent of an autopsy for humans. Tissue from every major organ is taken during a necropsy, examined and saved. If evidence of an infectious disease is found, samples are taken for culture to identify the organism. Some diagnoses are relatively simple, such as severe pneumonia or a malignant cancer.
Others require microscopic examinations of the tissue. Samples that were saved in formalin are sent to pathologists for additional tests. Pathologists can note subtle signs of disease that are difficult to pinpoint in an entire organ, identify specific cancers, and often identify organisms - bacteria, fungi and viruses - that cause disease.
Another purpose for a necropsy is to help the veterinarian learn the anatomy of different animals. In veterinary school, one learns about how domestic animals are put together, but this knowledge does not always extrapolate well to other animals. Functionally, elephants are supposed to be very much like horses, a theory that does help when a veterinarian's examining three tons of animal, wondering just where its kidneys are!
Q. What happens to the animals' bodies?
A. Tissue samples from necropsied animals are often sent all over the world for study by professional zoologists and medical personnel.
Many animals in zoos are managed by Species Survival Plans (SSPs) that collect data on all the captive animals of a specific species. The SSP managers often request that specific tissue samples saved from a necropsy be sent to a central location where they are examined again. This process helps identify diseases that seem to be common among a group of animals and allows managers to develop prevention protocols.
Tissue samples are also sent to researchers who are studying animal DNA, nutritional requirements, anatomy, hormones and many other things that will increase understanding of the needs and requirements of animals that are kept in captivity. The Saint Louis Zoo's Education Department is often notified when an animal dies, and the staff may collect a hide, some teeth or a skull. These biofacts are used to teach Zoo visitors to understand the whole animal that they see on exhibit.
Once a necropsy is complete, the animal is cremated or buried. By studying every animal that dies at the Zoo, we attempt to do everything we can to learn about diseases specific to certain groups of animals and to learn how to prevent infectious diseases that occur within a collection. Even after death, the Zoo's animal provide valuable assistance to education, conservation efforts and research.
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