Post-Mortem Selection of Specimens

Collection of samples from the field

Animals selected for laboratory analysis, ideally should be free from antimicrobial therapy and in an early or acute disease stage. Selected tissues should be collected as aseptically as possible. In addition, a meaningful history of the disease outbreak and a tentative diagnosis, based upon clinical evaluation, should be included. Laboratory tests results are directly affected by the selection, preparation, handling, and shipment of selected specimens.

Identify tissue and samples:

• Building or site

• Animal identification number

• Fluids, Exudate/Aspirates, Tracheal Washes, Urine

Preparation & Collection of Samples

Tissues - Fresh

Collect aseptically approximately 6 to 12 cm samples and place each in a plastic bag (e.g. whirl‑packs). Sample visible lesions with adjacent normal tissue. Double bag in whirl‑pack bags. Do not mix tissues in one single bag. Transport with cold packs.

Eighteen to 24 cm of intestine should be carefully removed from the mesentery and tied to prevent leakage of intestinal contents. Collect sections of small and large intestine. The selected, clearly identified samples are double bagged and sealed in whirl‑pack bags to prevent spillage. The sample should be refrigerated and cooled thoroughly prior to shipping.

Swabs

Aerobic culture: Commercial swabs with Stuart or Amies transport media is recommended to prevent desiccation.

Anaerobic culture: Note exposure to air for 20 minutes may destroy the sample. Transport in anaerobic transport media: for example a Clare Blair tube.

Virus culture: Collect blood in citrate tubes as EDTA may be detrimental to viral isolation. Dacron swabs are preferable over standard cotton swabs which may contain bleach which can reduce the viability of the viruses. The swabs must be prevented from dying out.

Histopathology

Preparation of Tissue for Fixation

Multiple sites or types of lesions should be taken. The sections should only be 2 cm thick. The small size of the tissue results in rapid and complete penetration of the fixative. Present normal looking tissue with the pathological specimen.

Normal lung left portion with pathological area on the right

Selected tissues should be cut with a sharp scalpel since the squeezing action of a scissors crushes and tears tissue. The tissue should be rinsed briefly with 0.85% NaCI to remove adhering blood, since blood will retard fixation. Autolysis or freezing will make samples unsuitable for proper evaluation. Place tissues in double whirl‑pales. Identify bags if multiple animals are submitted. Do not use narrow mouth bottles to submit fixed tissue. Note: All hollow organs (intestine or uterus) are gently flushed with 10% formalin without disturbing the mucosal lining before placing them in formalin.

Volume of fixation

The selected tissues are fixed in 10% Neutral Buffered formalin. Use 10 times the volume of the tissues being fixed.

Wrong bottle for tissue	Insufficient formalin	Correct formalin to tissue ratio
Tissue which floats formalin penetration assisted by placing a small piece of card over tissue (picture right )

Collection of samples Ideally collect samples from all abnormalities visually recognised and from the draining lymph node. In addition, collect from the following organs: lung, heart, liver, spleen, kidney, small intestine, large intestine, tonsils and two lymph nodes.

Blood Samples

Blood smear: Prepare the blood smear on the slide at the farm. Allow to air dry and stain back at the laboratory.

Unclotted blood sample: Collect in either EDTA, Heparin or Citrate tubes. Pig blood clots extremely quickly.

Clotted blood samples: serum or plasma – useful for biochemistry or antibody examination.

When sending paired serum, identify the acute samples from the convalescent samples on the tube and on the request form.

Packing Specimens

To avoid leaking in transit, double bag the samples. Whirl‑pack bags work well for this purpose. Wrap sample bags and 2‑4 ice packs on absorbent paper (e.g. newspaper) to absorb in the event of leaking. Place the package into a Styrofoam container. Completed submission forms should be inserted into the envelope on the inside cover of the cardboard box.

Mailing

Samples should be submitted by the fastest means possible to avoid deterioration of specimens. Next day or overnight delivery are preferred over others. Discuss with the mailing system selected any specific requirements. Ideally take the samples to the diagnostic laboratory personally or by carrier. Note try to avoid Friday or Holiday samples.

Ensure that all samples are adequately identified and a suitable history is provided with the samples.