Disclaimer: This blog is for educational purposes and cases described are not from any one animal. Please be warned that this blog contains pictures from real animal post mortems and graphic descriptions of disease.
I thought I’d start this blog with one of my more memorable encounters. Working in a pathology service, all our cases tend to be a combination of saddening and interesting, but this one was particularly so. A phone call had come in that morning, asking whether I would be happy to post mortem a snow leopard that had died unexpectedly. It was an exciting prospect (without a doubt the most exotic creature I’ve ever seen), but heart-breaking too; that the world has lost one of its 7500 only snow leopards.
My students had no idea what was on its way. Word spreads fast around the university and I was hoping to avoid a large crowd in the PM hall, so that my students could appreciate this beautiful animal up close in what might be the only time in their careers.
The leopard arrived in the early afternoon, with the curator of the centre where he had lived. The curator was also his keeper and a lovely gentle guy, very understandably upset by the sudden turn of events. Listening to the leopard’s history, you could see why. The previous day, like every day for the past five years, he’d been the picture of health: lively, jumping from platforms, with a strong carnivorous appetite. At midnight, keeper and leopard had their usual nightly rituals: secure enclosure, enough water, and access to shelter (not that English winter nights much compare to the leopard’s ancestral Himalayan conditions!).
The next morning the leopard was on a platform, lying dead on his front only a few hours after being checked.
On the PM table, he was as handsome as he’d ever been. There was no sign of injury, and only a tiny red dribble from the nostrils and mouth hinted that the leopard wasn’t just asleep (a scary thought when you’re looking into that mouth!).
It is common for a small amount of red fluid to be seen from the nose or mouth when an animal dies.
Under the skin, he had no bruising that might have been hidden by the fur, and a healthy layer of fat showed he was eating enough. The abdominal organs were nicely swaddled in fat, too, and there were big chunks of meat in stomach and intestines. Whatever had felled the big guy hadn’t slowed his appetite, which is often the first thing to go if an animal feels ill. There were some tapeworms too. This isn’t unusual, but I took some worms, pieces of meat, and gut samples to test for signs of damage or poisoning. Poisoning was very low down on the list of likely causes, but you only have one chance to take some of these samples.
Air hissed into the chest as I cut through the diaphragm – the large sheet of muscle used to breathe. You use this negative pressure to suck air into your lungs, so this was another normal sign. The negative pressure can be lost for a number of reasons; if a lung is punctured (by a broken rib after a fall, maybe), a stab to the chest, or a burst trachea (wind-pipe) or oesophagus (food-pipe). It can also happen after death, if the organs have started to decay and bloat the chest.
The tongue, trachea, oesophagus, lungs, and heart are all taken out in one go, as the ‘pluck’ (or ‘haggis’ if you’re Scottish!). The red fluid leaking out of the leopard’s nose was also seen inside his trachea and airways. The lungs, too, were a dark red colour. This leopard had always lived in England, but because they originally evolved to live at high altitudes, lung problems are sometimes seen. The heart was a normal size, but one of its chambers – the right ventricle – was slightly enlarged.
Congestion. The lungs, pictured here, and liver oozed dark red fluid from the cut surface.
The only other abnormality was very subtle; the liver oozed a darkish, almost blood-like fluid when cut. It seemed a bit congested; backed-up with blood from the rest of the circulation. Sometimes this makes the edges fat and round rather than sharply tapered (as is normal), and the liver overall can feel heavier.
So far, the likely cause of death seemed to be pneumonia or some sort of problem involving the heart or circulation, but none of the post mortem findings particularly stood out. Virology had turned up negative results.
Under the microscope, tiny crystals were visible in the heart and kidneys and briefly, heartbreakingly, poisoning seemed to be a possibility. Sometimes, meat from large animals such as cows which have been euthanised (humanely killed, usually due to injury or illness) is donated to institutions keeping large carnivores. The crystals looked like those seen in animals that have been injected with barbiturate, a chemical used by vets to painlessly euthanise animals. As we know from the horse meat debacle in the UK, it is not impossible for meat of unknown origin to get mixed up in the food chain. Had this snow leopard been accidentally fed a barbiturate-laden meal? Happily, this turned out not to be the case. Meat from the leopard’s stomach tested clean and so did barbiturate toxicity tests.
It is difficult to listen to the heart of large carnivores regularly – sedation or anaesthesia is necessary.
In the end, it all came down to a few cells. Looking under the microscope at his heart, the snow leopard had some areas with fewer heart cells. Heart cells conduct an electrical current over the heart in a very specific pattern, making sure the heart muscle contracts in the right way to pump blood properly around the body. If there are patches of missing cells, the electrical path gets disrupted and the heart may no longer pump in its usual, regular way. That’s what seems to have happened here. The leopard likely had an arrhythmia – an irregular heart rhythm – because occasionally his missing cells made his heart contract differently for a few beats. This snow leopard seems to have had a particular type of bad arrhythmia, stopping the heart from pumping properly, and causing blood to back up in organs around the body (like the lungs and liver). Unfortunately, this type of heart damage (the cause of which is unknown) can be present in animals for many years before an arrhythmia develops or is fatal, so there was little the keeper could have done to have prevented the death of this striking animal.
Large empty spaces (containing fat) where heart muscle cells should be. (x100, Masson’s Trichrome)
The heart of the problem.