Maybe it -should- happen to a vet

I had already decided to write a post about common pet poisons before this weekend, mainly motivated by a site that a friend of mine shared on Facebook, discussing the most common toxic materials that pets ingested. Reading through the article, it seemed to bear very little resemblance to my experience of dealing with poisoned animals.

The number one for pet poisons on the list was, as I remember, onions. Now, to be fair, this was a US-centric site, and it's just possible that animal companions in the States have a far more rapacious appetite for eye-wateringly bitter bulbs than those on this side of the Atlantic (or, and maybe just as likely I suppose, it's also possible that I have misdiagnosed a vast number of cases of onion toxicity in my career), but it struck that that almost none of the poisons mentioned were ones that I had seen cause a clinical problem in practice. Rather rudely, I hijacked my friend's thread to point out the substances which I saw regularly in practice. Afterwards, I decided probably the best thing to have done was just to blog about it myself.

I also wanted to blog about something that might actually prove useful to people - I know this in itself is stepping far beyond the normal boundaries of my blog, but what the hell, sometimes I just like to give something back . A less altruistic reason is that blogs with a 'Top 3' in the title tend be more widely read than those with a crappy pun for a title - I know it's depressing, but don't tell me you haven't occasionally been lured by the promise of the 'Top 5 Celebrity Hair-Related Injuries' or similar - so I decided to have a go at one myself for a change.

My plan was to start relatively light-hearted, and not make it too heavy. I'm sorry to say the light-hearted approach has somewhat gone for a Burton, because that was before I went to work on Saturday. This weekend I put four cats to sleep because they had been poisoned with antifreeze, all of whom lived in the same street. It's possible (maybe even likely) that this was a deliberate case of poisoning. I mention this not because I want talk about it especially (because it really was very depressing. Incidentally, if you're the type of person who might think 'Well, they're only cats - we poison plenty of rats to death, don't we?' - firstly, I do have some sympathy with that view. Humanity is very good at setting up strange double standards for animals. I may have mentioned in another blog treating a cat that was on a rabbit & chicken diet only, to then have as my next two consultations- you guessed it - a rabbit and a chicken. Secondly, whatever your position on how much animals can suffer (and trust me, they can suffer, terribly) please bear in mind there was quite a lot of human suffering and misery that accompanied these four deaths, too) but to drive home the point that we genuinely do see cases of these poisonings. They're still comparitively uncommon, but they can, and sadly do, happen.

So, that's the background. Below we're going to talk about the three poisons that I and my colleagues see most frequently in practice, with a few honourable mentions in the comments section. The eagle-eyed amongst you will probably spot this is a fairly cat-heavy blog. At first glance this is unusual, because cats are generally a little more discriminating about what passes their lips compared to their canine brethren. There's a couple of reasons felines are over-represented on the poisoning front, though. Firstly, they are (usually) physically smaller than dogs, and so generally need a much smaller dose of whatever the substance is to cause harm. Secondly, cat's livers aren't really as robust - as dogs, or ours, and they tend to struggle with a number of substances that we can manage quite readily.

1 - Ethylene Glycol - Antifreeze



The Stuff

Ethylene glycol is a nasty substance - it is toxic to us, and to dogs, but sadly it is especially poisonous to cats - mainly because of their smaller size than anything else.

Ethylene glycol is similar to alcohol, and in the early stages of poisoning, animals (and people) do appear to be drunk. This is rarely the difficult stage, though - the trouble comes when the body metabolises the ethylene glycol to other products. It reacts with calcium on the bloodstream to form calicum oxalate, and it is this that causes the harm, usually in the kidneys. There's an article here that describes the process far better than I can, and has lots more information antifreeze too.

How poisonous is it?


Short answer - very. For cats, the amount they need to take in is tiny - simply licking the outside of a cracked antifreeze bottle would almost certainly be enough to cause irreparable kidney damage. For your average 20kg dog, the lethal dose could be as little as a teaspoonful.

I was always taught that it's doubly dangerous because of it's sweet taste, and that cats would drink it voluntarily quite happily. I'm not at all convinced of that. In my experience, cats aren't especially excited by sugary treats, and antifreeze itself does not take good in my opinion (mind you, I think that about badger faeces too and both my dogs disagree) but it's poisonous enough that simply cleaning it off their fur is likely to give them a fatal dose.

Is there an antidote?

The other thing about poisons - people tend to assume there's an antidote, just like the exciting-looking vial of blue fluid that Indy spends the first act of Temple of Doom trying to grab. Sadly, in real life, it doesn't usually work that way, and the vast majority of poisons have not antidote at all, and you just have to deal with the symptoms.

That said, antifreeze poisoning dose have an antidote of sorts. As I say, the dangerous stuff is really the calcium oxalate that comes from metabolising the stuff. The enzyme in charge of the transformation is alcohol dehydrogenase, the same guy who's mops up all the wine you've got in your system after a crappy day at work. Give him enough alcohol to deal with, and he's so busy with it that most of the antifreeze gets peed out of your system without changing, and you're safe.

Great, in theory. The problem is the speed of ethylene-glycol related kidney damage. If you don't get the alcohol in within twelve hours of ingestion, you're probably too late. All you're likely to have seen by then, if you didn't see them actually drink the stuff, is a bit of wobbliness. The problem, for a clinical perspective, is that an awful lot of conditions cause a bit of wobbliness, and if we admitted them all and gave them intravenous vodka, we'd probably kill more cats than we saved.

The take-home message, then, is that if you know or suspect that your pet has taken in antifreeze, get them to the vets as soon as possible, and let the vet know that's what you're worried about.


Outcome

Pretty bloody awful, I'm sorry to say. The vast majority of cats (and it's usually cats) that present to us with antifreeze poisoning are already in kidney failure, and by then it's too late. Almost all of them end up getting euthanased.

So, if you have antifreeze at home, bear all of this in mind - clean up any spillages on the bottle, or on the drive, and keep pets away!

2 - Lillies




Another one for cats, I'm sorry to say - in fact, in a way this is even worse, because it is quite a common poisoning for kittens. They need an even smaller dose than adult cats, and they tend to be a bit more inquisitive.

The Stuff


Good question! As far as I'm aware, no-one is entirely sure of the mechanism of action for lily poisoning, but there are a number of points about it.

Firstly, it seems to be specific to cats - other animals may vomit or get diarrhoea if they scoff one, but for cats, lily poisoning leads to old enemy, kidney failure.

The second point it - whatever the toxin is, it is in every part of the lily. Secondly, the lethal dose, as with antifreeze, is miniscule. I've known cats that brushed against a lily plant and licked the pollen off their fur to end up with severe kidney damage.

Not every species of lilly is as poisonous as the others - there's a list of the toxic species here - but unless you're a horticulture expert, the best thing to do is just avoid them altogether when cats are involved.

How poisonous is it?


As mentioned above - very. Nibbling a leaf, petal or stamen can all be quite enough to destroy the kidneys.

Is there an antidote?


As no one is sure what the toxic substance is, no one can counter it. The only thing that can be done with lilly poisoning, as with a lot of poisoning, is damage limitation - try and prevent the bloody stuff getting absorbed. To the vet, this means putting the cat on a drip (to 'flush the system through' and support urine flow), making them vomit (if they ate the stuff within 30 mins - 1 hour) and preventing absorption from the stomach by feeding things like charcoal paste.

Outcome

Pretty crappy, I'm afraid. Just as with antifreeze, by the time you work out what's going on, it's often too late. I've had some extremely sad cases where lilies have been around the house due to the funeral of a family member, and as a consequence a few days later the family cat is brought in to us.

The vast majority of these cases get put to sleep too, I'm sorry to say. Take home message - either keep lilies well away from cats, or (my advice) just don't have lilies in a house where you have cats. It's too risky.

As with antifreeze, if you know or suspect your cat has been in contact with a lily, get it to your vets as soon as possible to try and limit absorption.

3. Rat-bait poisoning - Warfarin and the Coumarins



One of the classics - in that everyone seems to know a little about rat poison, and it's also probably the most suspected poison by clients of the three on this list - but that doesn't mean it never happens. Sadly, it does, relatively frequently. It's also one of those strange 'double-standard' poisons - it's dreadful if pets take it in, but it's fine to kill rats with it. I won't ponder the mysteries of the human mind any further though - I can't pretend I'm not a hypocrite either. I suppose we've all got to draw the line somewhere. Shall we press on?

Rat poison is the first on the list to affect more dogs than cats - largely because most cats have more sense than to tuck into a load of weird-smelling blue pellets.

The Stuff

Warfarin and the Coumarins may sound like a Glam Rock band, but they are actually the active ingredients of rat poison. You're probably already familiar with warfarin. It's mechanism of action is to inhibit an enzyme by the long-winded name of vitamin K epoxide reductase - and it's this enzyme that has the job of recycling used vitamin K in the system. Without it working, you run out of vitamin K very quickly.

Vitamin K is a vital component in the 'coagulation cascade' - a group of proteins which, along with protein, allow your blood to clot and prevent it from all leaking out of you when you are lightly burst. Without vitamin K, a number of these proteins fail to form, and without them you're at risk of bleeding to death.

Warfarin (I'm sure you're aware of this but I'm telling you anyway) is used at low doses in human medicine to 'thin the blood' - what it actually does is reduce your risk of getting a clot within your bloodstream (a thrombus). What you might be less aware of is that it isn't used in rat poison any more, because almost all rats are greatly resistant to now, on account of humanity feeding them lots of it down through the years.

The coumarins (of which warfarin is a so-called '1st generation' one - nothing to do with Captain Kirk) are used instead nowadays - usually 3rd generation ones such as brodaficoum or difenacoum) all work in a similar way to warfarin, the main difference being that the more modern drugs work for much longer, and are far more potent.

The symptoms of this kind of poisoning are the sort of thing you would expect - blood, from anywhere. If a dog is bleeding in two unrelated sites (for instance in the pee and from the mouth) or if there are tell tale signs of bleeding in the gums or the eyes (petechial haemorrage) then rat poison is on our list of diagnoses. Lethargy is another common sign due to the anaemia, as well as blue-coloured vomit or faeces (simply from the blue dye in the pellets - just like slug bait poisoning)

How poisonous is it?

The answer to this very much depends of exactly which coumarin has been eaten, but as most rat poisons are second- or third-generation nowadays I'm going to refer you to my sadly standard answer - very. We can work out the exact doses, but basically if your dog or cat has definitely eaten any amount at all, it could be in trouble.

Is there an antidote?

By now you might well have read how the coumarins work, and you can probably take an educated guess at the antidote if you don't know it already - Vitamin K.

As with all poisons, the best thing you can possibly do it get in early and prevent absorption as soon as possible. If you can't get to it in time, vitamin K will do the job, but it takes 24-48 hours to work, because it needs to get synthesised into the clotting factors, so the dog usually has to stay in the practice on fluids, and occasionally will need a blood or plasma (basically blood minus the red blood cells - easier to store and transport, and gives the dog a whole load more clotting factors to work with) transfusion if the bleeding is too severe.

Coumarin drugs remain in the system for a long time - the dog is likely to have to take vitamin K supplements for 3-4 weeks after the poisoning incident.

Outcome


Refreshingly, the outcome is often better than the other two toxins we've discussed already. Partially because people are well aware of the poisonous nature of the substance (it is called rat poison, after all), and partially because the antidote can work even a few days after exposure, we generally have a good chance of getting animals dosed with rat poison through. Sadly, we still see some cases too late or too far gone to influence the outcome, but fortunately these are the minority rather than the majority (unlike lily and antifreeze poisoning)