A post mortem examination should be performed on all aborted foetuses and neonatal deaths. It is particularly important to rule out Equine Herpesvirus 1 (EHV-1, see HBLB Code of Practice). The whole carcass and placenta can be submitted to Rossdales Laboratories for examination; alternatively the carcass can be examined in the field using the protocol below and the required samples submitted using the form HERE. Photographs are often useful and can be emailed to firstname.lastname@example.org.
- Large, flat, easily disinfected surface.
- Sharp clean knife/scalpel, scissors
- Sterile scalpels and forceps (for PCR samples)
- Protective clothing & disinfectants
- Two sterile universal pots
- Three charcoal swabs
- Gas flame and palate knife (for collecting lung and liver swabs)
- Formalin (10% buffered formalin) & container(s)
- Tape measure, scales (if available)
(1) External examination:
- Examine the foetus externally (mucous membranes, state of autolysis, body condition, meconium staining etc). Ideally measure the crown to rump length and weight (not always feasible in the field).
(2) Sampling for PCR:
- With the foetus in right lateral recumbency reflect the left forelimb, reflect the left hindlimb (cutting through the inguinal region and hip joint) and remove the skin over the abdomen and thorax.
- Carefully open the abdomen and thorax: initially cutting dorsoventrally from the paralumbar fossa then cranially along the ventral midline, through to cartilaginous costosternal junctions to the thoracic inlet. When cutting through the rib cage try not to touch the viscera with the blade or hands. In all but late term fetuses the reflected ribcage can be secured in place by simply fracturing the ribs along the costovertebral articulations manually. Make a note of any effusions present – a marked yellow-amber clear or gelatinous effusion in the thorax is highly suspicious for EHV.
- Using a sterile scalpel and forceps take samples of thymus, lung, liver and spleen into a universal container (<1cm3 of each tissue is adequate)
- Using a sterile scalpel and forceps take 3-4 small (10p piece size) sections of chorioallantois into a separate universal pot.
(3) Samples for bacterial culture.
- Using a gas flame sterilize the palate knife and a scalpel by heating until starting to glow.
- Use the palate knife to sear the surface of the lung then cut through the pleura in the centre of the seared area with the scalpel.
- Take a swab through this cut, pushing the swab deeply into the underlying parenchyma.
- Repeat for the liver.
4) Samples for histology.
The order of sampling can vary, but samples should all be <1cm thick in at least one dimension to facilitate formalin fixation. Place the tissues in 10% neutral buffered formalin, with a ratio of at least 1:10 volume of tissue:formalin
- Collect a sample of the thymus and spleen into 10% neutral buffered formalin. Remove and discard the spleen.
- Collect the adrenal glands. (Move intestines out of the way and the adrenal glands can be found between the kidneys and aorta).
- Cut along the jugular groove down to the trachea, and remove and sample the thyroid gland.
- Cut through the trachea proximally and remove the pluck (trachea, lungs, heart and aorta).
- Open the heart to check for congenital defects by opening both ventricles and atria. Take a sample of the left ventricular wall, ideally including one of the papillary muscles.
- Incise through the lungs. Take 2-4 representative samples. Lungs that feel firm +/- multifocal haemorrhages and pleural oedema are suspicious for Herpes.
- Remove the GI tract en bloc. Check the stomach contents (eg for meconium ingestion) and for any other congenital GI defects. Histology of the GI tract is not normally indicated, but samples can be collected.
- Remove the liver. Take 2-3 samples from different lobes. The liver may be very autolysed (almost liquid) if the foal died in utero some time before abortion e.g. umbilical cord torsions. In EHV cases the liver is often fairly firm with white spots (areas of necrosis) – if present try to include these areas in your samples.
- Remove the kidneys and take a representative sample of each. The renal cortices may be very autolysed (liquid) if the foal died in utero some time before abortion.
- Open a selection of joints to check for haemorrhage or effusions. Check for cleft palate, scoliosis etc.
5) Examination of the placenta.
- Cut the amnion from the umbilical cord close to its attachment to the cord, examine and sample (1-2 representive sections).
- Measure the length of the umbilical cord – total and intra-amniotic lengths. Examine for twists, oedema, congestion, urachal dilatations, splits in the surface epithelium, exudate and yolk sac remnants.
(Photos are often helpful here). Sample any lesions – no more than 1cm thick.
- Lay out the chorioallantois in an F-shape and examine for completeness
- Swab any surface exudate for bacteriology.
- Take an approximately 10cm long, 1cm wide strip starting at the cervical pole and progressing cranially for histology (formalin fixed). Collect additional small samples of each horn and the body, and any specific abnormal areas.
- If scales are available placental weights, particularly that of the chorioallantois, can be useful (remember to remove all the fluids before weighing).
Clean up and disinfect.