Below you will find some helpful hints for preparing and collecting samples during a necropsy.
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When it comes to SAMPLING, having all your equipment labeled and laid out in advance makes a HUGE difference! If the necropsy is to be performed in the field, having pre-made FIELD SAMPLING KITS with PRE-PRINTED LABELS will help considerably. If the necropsy is to be performed in the laboratory, there are now computerized label-makers that print onto adhesive labels that will last for many years, even on tagged samples placed in formalin or in -80C storage. Standard sampling equipment for small marine mammals includes, KNIVES, SCALPELS, SCISSORS, FORCEPS, A CENTIMETER or MILLIMETER SCALE for photographs, and SAMPLE CONTAINERS such as WHIRLPAK BAGS, CRYOVIALS and BLOOD TUBES. Don't forget equipment to open the skull, such as (ideally) a STRYKER SAW. In a pinch a regular hand saw can work, particularly if you have a vise to hold the skull. |
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Start out by doing a good EXTERNAL EXAMINATION. It is better to collect samples for CULTURE as soon as possible to avoid contamination. |
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Here the prosectors are collecting a PREPEUTIAL SWAB for bacterial culture. Notice that the sampler is handling the swab ONLY BY THE EXTREME END and is WEARING GLOVES to avoid contaminating the bacterial swab with human skin bacteria, a common mistake. To get the most accurate results for swabs taken from internal organs, abscesses or other lesions, lightly SEAR the surface of area of interest first with a flat blade heated over an alchohol burner or lighter. Next PIERCE your seared surface with a sterile blade. Finally, PUSH the bacterial SWAB into the tissue or lesion through the pierced area to sample bacteria present in the wound, without contaminating the swab with surface bacteria. In this way you can most accurately sample bacteria associated with the organ or lesion. |
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When possible it is helpful to have a SECOND PERSON act as assistant and notetaker during the necropsy. This will speed up the process considerably. |
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It is common to collect and archive BODY FLUIDS such as SERUM, PERICARDIAL FLUID, BILE, URINE AND CEREBROSPINAL FLUID (CSF) during a necropsy. These fluids may be used for a variety of purposes, including ANTIBODY TESTING, TOXICOLOGY or TESTING FOR THE PRESENCE OF PATHOGENS through CULTURE, PCR or other means. Most samples can be easily collected using a needle and syringe. It is best to NOT recap the needle by hand or to hand a syringe with a bare needle over to someone else as these fluids can contain pathogens transmissible to humans. If the needle must be recapped, it should be dome by sliding the needle back into a cap placed on the necropsy table. Disposal of the needles in an approved biohazard container is advised. |
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When collecting samples for LONG-TERM STORAGE or toxicology, it is best to save them in an inert material such as TEFLON. This is because TEFLON: 1.) Lasts longer than foil, 2.) Does not contain ingedients that may comprimise subsequent toxicological testing, 3.) Unlike plastic, teflon does not appreciably absorb pollutants or interfere with their analysis. Thus teflon sheets are the material of choice for long-term tissue storage. In the above photograph, the prosector is placing tissue to be archived into the center of a teflon sheet. Depending on the protocol followed, additonal sampling requirements may include use of special (eg teflon) knives for sample collection and pre-rinsing the teflon with a solvent prior to use. A reasonable sample size for long-term storage for toxicology is approximately 50 GRAMS. Whenever possible, long-term storage should be in -80 C or at least -20 C freezers. Storage of samples in a regular refrigerator-freezer will lead to rapid sample degradation. |
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Once the sample is wrapped in teflon sheeting it can be placed into a pre-labled whirlpak bag to facilitate long-term storage. |
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When collecting sterile samples in a whirlpak bag, avoid contaminating the sample by touching the inside of the bag with your fingers or blowing into the bag to open it. This is a COMMON mistake! |
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To close a Whirlpak bag, simply fold the bag over itself several times by grasping the yellow top, and then fold the yellow tabs inward to seal the bag. If the sample inside is wet and will not be frozen, shipping this bag inside a larger whirlpak bag will avoid leakage during shipment. To ship larger volumes of moist or wet material, such as feces or stomach contents, we recommend sterile 50cc or larger screwcap conical tubes. |
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This is a photo of the yellow "chicken fat" clot that can sometimes be located within the heart, liver or great vessels at necropsy. It is the same as the large yellow clot that can be seen at the top of blood tubes collected from live aninmals. When collected and centrifuged separately from the red blood collected at necropsy, it provides abundant, good quality serum to bank for serological testing. |
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A closer view of a "chicken fat" clot. We find it easiest to place this in a clean plastic cup and cut it several times with clean scissors to make it easier to load into blood tubes for centrifugation. |
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When collecting bullets or any other lead projectiles from necropsied animals, here are some simple rules to follow: 1.) NEVER grasp or touch the bullet with another metal object, such as forceps. Simply push it out of the tissue with your fingers and catch it in a gloved hand. Metal instruments can scratch the bullet and efface forensic clues as to the type of weapon and specific weapon that fired the bullet. 2.) WASH any remaining soft tissue off the bullet with tapwater and DRY the bullet carefully in a soft towel. 3.)The bullet should be WEIGHED, MEASURED and PHOTOGRAPHED and the trajectory that the bullet(s) took through the tissues should be noted. 4.) ALWAYS store bullet(s) removed at necropsy separetly in DRY, in PAPER envelopes. This will avoid corrosion. SEAL the bullet in a prelabled envelope and hold it in a restricted access, locked cabinet until examination. HELPFUL TIP: To facilitate finding a small bullet in alot of tissue: 1.) CUT the tissue carefully into smaller pieces 2.) LAY the pieces out separately on a plastic cutting board 3.) take a radiograph (X-ray) of the tissues by laying the cutting board over an X-ray plate without disturbing the tissue. 4.) The lead projectiles will show clearly on the film so that most of the pieces can be eliminated. 5.) Use the silhouette of the positive piece to figure out where the lead is. Feel it to see if you can find it. If need be, cut the tissue into smaller pieces and repeat the radiograph. |
