Chief should have a good shot Brittany -- it is mostly young dogs who die from parvo and mostly from the Corona virus that lives IN parvo.
How? Depends on how old he was when he was vaccinated. I know it's been "disputed" but if a pup still has Mom's 'immunity' effective in his system when he gets vax'd the shot won't take. And if he's gotten vax'd with killed vaccines they aren't going to give the immunity they should.
so if a pup gets a shot at 6, 8, and 11 weeks -- it's possible -- actually probable, that the first two are ineffective, and maybe all 3. If Mom was healthy and he got lasting immunity from her, and the shots came too soon, that's how it happens.
Add to that, what someone said above -- at 5 months he's starting to sexually mature. That DOES weaken their immunity (yes, Jennie exactly -- all the same things that 'trigger' demodex can trigger any other illness simply because they are drains on the immune system).
So particularly if he was snacking on a pig that wasn't healthy and the immune system was drained by battling THAT bacteria, then the harder punch from the parvo could surely prevail.
No vaccine is ever 100%. It's just plain not. It is simply trying to get the body to build anti-bodies to help immunity. But if is last shot was the only thing he got after mom's immunity laxed, then it didn't get boostered (which is supposedly how it happens).
Now -- he should be immune to the virus that caused his own illness -- but only a vet can tell you that one.
HOW can it have gotten on your property? Easy -- you've had kids on your property that didn't belong there, and other people have been there. All it takes is literally a couple of molecules of parvo virus to spread it -- way too tiny to 'see' -- a tiny bit in dirt on someone's shoe who walked to their own car on their own driveway because the neighbor's dog was sick and the paperboy tracked it from that house to their house. They got in their car, walked on your property and it was there. You could have picked it up on your own shoes just from walking into the grocery store and back to your car. It can be anywhere -- this is why the big huge mega deal about vaccinating got started -- it's just so darned easy to spread.
A basin of chlorox isn't really enough. You have to create a clean room atmosphere -- BEFORE you leave your car change your shoes. Walk from the car to the house and CHANGE SHOES BEFORE you enter. (so essentially you dedicate a pair of trash shoes to go between your car and your house)
After a week the shoes that have gone between the car and house need to be destroyed and do the same with some other pair.
Frankly you should roll up your pantlegs before you get out of the car. And one of the first things you need to clean is the carpet in the car -- and chlorox it if at all possible. Every floor surface in the house (including your stairs if you have any -- going upstairs or downstairs into a cellar) needs to be chloroxed if possible. Because you've gone a LOT of places in the past 9 days and it takes at least 9 days for it to incubate.
I doubt bleaching just that spot of the carpet will work. Now I've done this before and it's not pleasant -- but if you go to a store that rents carpet shampooers -- you can actually put chlorox in with the soap. If you have an old yucky carpet it will clean it -- I've actually bleached my nasty orange carpet in my dining room several times. I expected it to fall apart after the first time but it's not only ugly it's durable.
It's not something you want to do with a carpet you care about. But you have to get DEEP because that virus will have gone all the way to the padding.
But don't kid yourself that it's only that one spot -- he's walked in his poop outside -- he's tracked it all over so everywhere he walked in your house ... and then when you stepped where HE stepped you tracked it further. Does that make sense? You don't have to see or smell poop for this to spread -- literally it's microscopic particles that will travel.
If the new pup is gonna get it, he will get it. It's not impossible to live thru parvo, Brit -- truly it's not. I don't mean to sound hard-hearted at all. But a lot of folks on here have brought pups thru parvo. it's hard -- you have to keep them hydrated, you have to stay up with them round the clock. But it can be done.
You will likely need to replace some sod -- particularly where the pup is going to need to potty.
You can't vax the pup now -- a vaccine takes at least 3 weeks to really form immunity. And a vax with a modified live could be disasterous.
Now Chief will shed parvo in his stool for a while -- until his body defeats the virus and fully forms anti-bodies. this isn't like something bacterial that can be killed by antibiotics. Virus doesn't work that way.
If you want to pm me I can tell you some herbals you can give the pup to boost his immune system and give him a better chance.
The other thing you need to ask the vet is will your livestock get parvo? I don't know -- I have NOT a clue if it's at all zoonotic. But you need to ask it.
And -- frankly, if you have coyotes, then that's another possible way he got parvo. Because all they'd need to do is track it from one place to another and coyotes probably can get parvo because they are essentially canids of a sort.