Foodie Friday

Foodie Friday

How would you describe this microscope slide?

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sesamoidstreet: It looks like a crunchie bar.

vetforensics: Multiple sections from tissue of unknown origin are examined.  The sections are composed of a crystalline matrix–

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vf: –interspersed with regular, ovoid, refractile material.  No cells or other connective tissues are observed in the examined sections to suggest an anatomical location.

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vf: The changes are consistent with a crystalline structure, likely from a urolith, centre of a chronic abscess, or other mineralised accumulation.

ss: It’s actually…

crunchie2

ss: … a crunchie bar.

(Beware over interpreting histology.)

crunchie

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What's this?

Who’s this? Wilbur the rove beetle, of course!

Last week we asked why this guy is such a big deal in pathology. Pakasuchus came very close in guessing – although Wilbur is alive and kicking, the body he lived in most certainly was not!

Wilbur and his bug buds are important to pathologists because they are the best way to figure out the time of death. The study of insects (and other arthropods) in decomposing remains is called forensic entomology. Wilbur is a rove beetle (Ocypus sp.), and eats maggots that infest dead bodies. Bugs ‘colonise’ bodies with a very particular timing and in a very specific order depending on the conditions around them, which forensic entomologists use to estimate the time since death.

The order can vary hugely, but generally the first wave of colonisation brings blow flies, attracted by the smell of blood, body waste, and general death odour, which lay their eggs on the body. These flies in turn attract further fly species (including the appetisingly-named ‘cheese flies’ and more conventional corpse flies), and along with decomposition, sets up the second wave of colonisation. The third wave, attracted by rancid fat, arrives, and now that the body is popular the more hipster members of the first wave get bored and move off.

Doesn't just eat cheese!

Doesn’t just eat cheese!

Eventually, Wilbur and his beetle buddies muscle in on the action. Some feed off the rotten juices, others tackle drying tissue (too tough for the flies), but Wilbur likes his meat fresh – other bugs are the plat du jour!

Wilbur's dinner!

Wilbur’s dinner!

Although most people are familiar with forensic entomology in human murder cases, it is also used to determine time of death in animal cruelty cases.

Bugs can also be a valuable source of other evidence too. Different creepy crawlies obviously live in different places, so can identify the geographic location of death. But they also have very specific local preferences too; some preferring sun, others shade, and even some indoors! They can tell you where the body was at the time of death, and where it has been since – useful for tracking the footprints of bad guys (and zombies).

They might tell you about the circumstances that an animal has come from. Certain flies are attracted to urine and faeces and their presence on a body suggests that the animal may have lived in a confined area surrounded by its own waste prior to death.

If the body has been in a fire, insects can survive safe inside the skull munching on grey matter,  telling you whether the animal died before or during the fire. If the latter, they will also tell you the time of the fire.

Usually different body tissues are sampled to test for the presence of drugs or poison, but if the body is too rotten or otherwise destroyed (e.g. burned), maggots can be tested instead! Having no arms or legs, maggots can’t hold on and frequently fall off the body. DNA can also be recovered from these maggots’ stomachs, to prove the body was in a certain place or in cases where it hasn’t been found.

Even no bugs at all is an entomological clue! Lack of insects on anything but a fresh corpse suggests that it has been frozen, kept in a tight container, or buried very deeply underground.

the more you know

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Cases

A shot in the dark

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.

This was a case with a couple of twists. It started with a dog whose skin felt just a little strange. He came to his vet, and it sounded as though his chest and front leg was covered in bubble-wrap, crackling when touched. This is how air trapped under the skin (tissue emphysema) feels. Tissue emphysema commonly happens after traumatic injuries, where outside air is forced through wounds under the skin, or alternatively, can escape from the lungs after chest injuries.

Bubbles of air and oedema in the subcutaneous tissues

Bubbles of air and oedema in the subcutaneous tissues

Hidden under the dog’s fur, there were indeed several shallow wounds. X-rays revealed three air rifle bullets lodged in the dog’s foreleg, ribcage, and abdomen. The vet operated and retrieved the bullet from the abdomen.

During surgery, everything seemed fairly ok. Air rifles are classed as ‘low velocity’ guns, meaning the bullets travel under a thousand feet per second (unlike high velocity bullets which travel over 2500 feet a second). The surgeon checked carefully, and it seemed that the bullet hadn’t directly entered the intestines or any organs.

The bullet hole in through the abdominal muscles, but no direct intestinal perforation....

The bullet hole in through the abdominal muscles, but no direct intestinal perforation….

But then, shortly afterwards, things took a negative turn. The dog developed a fever, rapid, unstable breathing, and dependent oedema – signs of sepsis, or blood poisoning. Unfortunately, this carries a poor prognosis and high chance of suffering, and he was euthanised on humane grounds.

Bullets cause damage by cavitation; tissues in the bullet path balloon and stretch, tear, and then finally contract. Because of this, tissue damage is not necessarily confined to the direct bullet path.

Tissue cavitation creates a negative pressure that sucks hair and contaminants into the bullet wound. In the post mortem, it became clear that damage extended far beyond the bullet’s path. It seems that even though the bullet hadn’t penetrated the intestines, it had damaged them. Faecal material leaking from the guts was combined with debris sucked into the wounds, setting up a huge infection in the abdomen, chest, and tracking under the skin. The chest, abdomen and subcutaneous layers were filled with litres of watery, red fluid – oedema and blood, a result of massive inflammation due to infection.

Lots of oedema and bleeding under the skin - look how wet those tissues are!

Lots of oedema and bleeding under the skin – look how wet those tissues are!

Sadly, as pathologists we can find out how an animal died, but in some cases we cannot fathom why.

One of the other bullets, lodged deep in a muscle

One of the other bullets, lodged deep in a muscle

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