Necropsies: Post-Mortem Exams Help The Living
Scott Stahl DVM. ©1996 League of Florida Herp Societies, Feb/Mar 1996
One of the most important things a herpetoculturist can do to better manage his or her collection is to obtain as much information as possible from any herp that dies. The loss of an animal is always discouraging, but it may provide an opportunity to gain valuable insight on husbandry practices (quarantine, diet, watering, housing, etc.) and diseases (bacterial, fungal, parasitic, viral). Ultimately, this may help prevent future losses within the collection.
Making a diagnosis is much easier in a deceased animal than in a living animal. Many of the diagnostic tests (radiographs, blood sampling) that we perform on live herps are attempts to find out what is happening inside the animal. While these tests may be helpful they may not provide precise answers to the problem. For example, an x-ray may show an enlarged liver, but it will not necessarily tell us what has caused the increased liver size. Bloodwork may reveal elevated liver enzyme values--which would indicate liver damage--but it does not tell us what has caused the damage. For reptiles, I have found that exploratory surgery is one of the most valuable diagnostic tools in practice. That is because it allows the veterinarian to actually look inside the reptile's coelomic cavity and visualize organs such as liver, kidneys and intestines.
Similarly, a post-mortem (after death) examination is extremely valuable because it provides an opportunity to examine everything, both inside and outside. The post-mortem examination of an animal is called a necropsy (nec = dead, opsy = to view). It is similar to an autopsy (= to see with ones own eyes) which refers to a human post-mortem exam. Obviously, the necropsy will allow a thorough visualization of all internal organs.
There are several components to consider when performing a full necropsy.
For starters, historical information should include:
Information related to death, such as:
Often, I find that many owners will not provide this kind of information but will wait instead to see if the necropsy will verify those circumstances as the true cause of death. It is best to share this information with your herp vet so that he or she can have all the necessary information for making a diagnosis.
of the Herptile for Necropsy
The best thing to do if you find you have lost an animal is to run it under cold water to cool the body down. Then place the animal in a sealable container (like a zip-lock bag or plastic trash bag) and place it in the refrigerator. Do not put the carcass in the freezer! Freezing the carcass results in the animal's cells rupturing when thawed. This makes it much more difficult to determine the cause of death.
The carcass should be kept in the refrigerator until it is transported to your herp vet for the necropsy. Try to keep the reptile cool during the transportation. The sooner you can get the animal to your veterinarian, the better, However, the body will likely stay in fair condition for a day or two in the refrigerator if you cannot get it to the vet immediately. If you know that you cannot present the animal for necropsy within a reasonable period of time (usually 3-4 days is the maximum for maintaining a quality specimen in the refrigerator, depending upon how autolyzed it was prior to refrigeration), then you may have to freeze the specimen so you can present the specimen later for necropsy. Although frozen specimens will limit some of the testing that can be performed at necropsy, valuable information can still be gathered.
The herp is then weighed and external features are examined for any abnormalities. The skin is checked for bruising, bleeding, ulcerations, burns, lumps, scars, retained shed, ectoparasites, etc. Other external features that will be examined include the nares (nostrils), eyes, ears, oral cavity, phyarngeal (throat) area, cloaca, reproductive appendages, scent glands, etc. The musculoskeletal system is also examined to assess the body condition (muscle mass) and palpated for any abnormalities such as soft bones or bone fractures.
After a thorough exam, the herptile abdomen is opened for inspection of the internal organs. In chelonians this involves removing the plastron (bottom shell). Initially, the coelomic cavity itself is examined for evidence of free fluid, blood, or infection. All organs are examined systematically to avoid missing anything. Important internal organs that should always be examined include: heart, great vessels, lung, thyroid gland, liver, gall bladder, spleen, pancreas, esophagus, stomach, small intestine, large intestine, adrenal glands, kidneys, gonads (testicles or ovaries). Organs are cut into in order to examine full thickness sections and the internal portions of tubular organs such as trachea, lungs, heart, esophagus, stomach, and the intestinal tract. The color, size, shape, and any abnormalities are noted for all tissues. Cultures for bacteria or fungus may be taken from organs that appear abnormal. Fecal material may be collected from the intestinal tract for parasite analysis or culture.
These tissues are placed in a 10% buffered formalin solution which will preserve them indefinitely. It is important to have the proper ratio of fluid for the tissues being preserved. A good rule of thumb is to have a 1:10 ratio of tissue:fluid to ensure the fluid will preserve the tissues properly. The tissues are then transported to an appropriate laboratory for processing and analysis. At the laboratory the preserved tissues are prepared by embedding them in blocks of paraffin wax. The blocks (containing the tissue) are then thinly sliced by a special instrument called a microtome. The shaved pieces are then mounted on slides and stained in order to highlight the cells for examination under a microscope. A pathologist experienced with herps can then examine the different tissues microscopically, looking for clues to the cause of death. It is important to give the pathologist as much information as possible on the history and the findings of the gross examination for the tissues presented. The pathologist will then send out a report with a summary of his or her findings, usually including the most likely case of death. Results of other tests, such as culture and fecal analysis, are also taken into account.
Now let's review a few cases so you can see the value of a complete microscopy.
The snake had been in the owner's possession for seven months. During a quarantine period, several fecal examinations were done to check for parasites. All were negative. Several new snakes had been added to the same rack system over the seven months. Even though the owner had quarantined the animals and had several fecal exams performed, the possibility of an infectious disease was a concern. Gross Examination: The snake was in good body condition, and no external abnormalities were noted. However, examination of the coelomic cavity revealed many abnormal-looking organs. Most notably the heart, liver and kidneys were enlarged and a pale white-yellow color. The intestinal tract appeared normal and no abnormal parasites were found. Tissues were collected and sent off to histopathology.
Histopathology: Microscopic examination revealed cancer cells in all tissues presented. Cancerous lymphoid cells had infiltrated and damaged most of the major organs including liver, heart, kidneys, and testicles. A diagnosis of lymphosarcoma/lymphoid leukemia was made. Sometimes this type of cancer may be associated with a virus, so electron microscopy was used to search for evidence of viral particles. None were found.
The value of the full necropsy in this case is evident. It helped the owner learn that his snake died from a very unusual disease. He had not made mistakes in his care, his quarantine had not broken down, and no infectious disease had entered his snake room. The peace of mind from this information was worth the effort.
Gross Examination: The snake was found to be gravid with a large number of oviductal eggs (yes, they are still called eggs at this point even though boas are live bearers). Most were not fertile but several contained developing embryos. One of the unfertilized eggs had been damaged and had leaked yolk material into the coelomic cavity, causing a severe peritonitis (infection in the coelomic cavity). The outer surfaces of several organs were covered in some of the yolk material, but the rest of the organs appeared normal otherwise.
Histopathology: Even though the cause of death was likely evident from the gross examination, the owner pursued histopathology to learn as much as possible about this animal and to gain insight into other losses in the collection. The results of the microscopic examination revealed bacterial invasion of the liver related to the egg yolk that was released into the coelomic cavity as the cause of death. The free egg yolk created a severe inflammatory reaction from the snake's immune system with subsequent bacterial involvement which led to sepsis (bacteria entering the blood stream). Perhaps just as important was that the histopathology showed no evidence of viral inclusion bodies, cryptosporidia or other devastating infectious agents that may have caused the loss of the other two boas.
As you can see, the post-mortem examination is a multi-step process. While the cause of death can sometimes be obtained from the gross examination alone, much more information can be gained by also including histopathology. In most cases, histopathology is necessary to get specific answers, and it is especially useful in ruling out involvement of infectious agents. Histopathology may also reveal organ failure, which can sometimes be related to nutrition problems or dehydration. This could provide valuable information about husbandry practices.
So remember: avoid freezing dead herps if you plan to pursue a necropsy that will include histopathology. Most importantly, don't miss the opportunity to learn from the loss of a herp in a collection. Otherwise, a wealth of information may be lost forever.
Need to update a veterinary or herp society/rescue listing?
Can't find a vet on my site? Check out these other sites.
|Clean/Disinfect||Green Iguanas & Cyclura||Kids||Prey||Veterinarians|
|Home||About Melissa Kaplan||CND||Lyme Disease||Zoonoses|
|Help Support This Site||Emergency Preparedness|
© 1994-2014 Melissa Kaplan or as otherwise noted by other authors of articles on this site