This is gonna be lengthy, but I’m bored this morning…
As a veterinary pathologist who did rabies testing almost daily for 25 years, and had extensive experience working with wildlife species… I’m going to go out on a sturdy limb and postulate that your skunk was more likely in the terminal throes of infection with canine distemper or rabies virus than errant poisoning.
As one of my aged professors opined…“The most common things happen most often.”
Outbreaks of canine distemper virus infection happen very frequently in raccoons, skunks, etc. In the absence of hunting/trapping, populations build, unfettered, until just such a disease outbreak comes along to knock that population back to sustainable levels. Rinse, repeat.
In this part of the country, skunks, carrying the North-Central Skunk strain of Rabies virus, are the principal sylvatic (wildlife) reservoir of Rabies.
That said, proper protection to limit exposure of non-target species to any ‘poison’ is important.
There are three principal types of commercially-available rodenticides commonly in use today; all are potentially toxic to most mammalian and avian species, but potential for ‘secondary’ toxicity - consumption of the poisoned ‘target’ animal by predators/scavengers - varies from class to class:
Bromethalin, a neurotoxin, has no effective antidote, but it takes a lot to kill… rats/mice have to consume a LOT to achieve kills. ( In my experience, it’s not a very effective rodenticide, if they have access to other foodstuffs.) Dogs are less sensitive to it than are rodents…but if a small dog eats a full bag of bromethalin baits, the outcome could be bad. Our 60# Border Collie recently ate one bait block that my wife had accidentally allowed her access to, while cleaning up after a major field mouse infestation we’ve been dealing with… but it was at least 12 hrs later before we realized it. She never showed any signs of illness, but I induced vomiting anyway, and spiked her food with osmotic and bulk-forming laxatives for a couple of days. At this point, we don’t really know what the potential for ‘secondary’ poisoning is for bromethalin.
Anticoagulants…started many years ago with Warfarin, but we’re now on at least third-generation compounds that require prolonged (weeks to months) Vitamin K replacement therapy in the event of accidental ingestion. The anticoagulants pose the greatest danger to secondary consumers.
Vitamin D3(cholecalciferol) analogs…essentially make the target animal’s cells take up excessive amounts of Calcium, causing mineralization of tissues such as stomach, kidneys, heart muscle. blood vessels. There appears to be little to no worry about ‘secondary’ poisoning (predators/scavengers eating poisoned rodents) with the D3 rodenticides, but for accidental consumption… there’s not a lot you can do other than induce vomiting ASAP. I’ve seen tissues from dogs that ate Vit.D3 rodent bait… internal organs essentially ‘turn to stone’… there is extensive mineralization of kidneys, stomach wall, myocardium, blood vessel walls.
Now, beyond that, there are numerous poisonous compounds that are still commonly employed - in an illegal manner - to poison nuisance wildlife (and sometimes, maliciously, to poison ‘nuisance pets’). Strychnine is hard to come by, but still used by some folks. Carbofuran (a carbamate insecticide used in forestry and (some) crop production) has been widely used (again, ILLEGALLY) to spike carcasses, baits, and even soft drinks like Mountain Dew to kill unwanted predators/scavengers - but folks have ended up going to jail (as they should), when that spiked deer carcass ends up killing eagles/hawks, neighborhood dogs(though they might have needed killing), etc.
Ethylene glycol-based automotive antifreeze is toxic - and evidently tasty - to mammals… I’ve seen numerous animals poisoned - either accidentally or intentionally - by ingestion of antifreeze (in open containers when folks were changing fluids, or even overflow puddles in the garage/driveway - and by malicious incorporation of it into baits, like tuna.)