Rats

If it doesn't come apart, I would give it a thorough spray with dettol, leave for 10 mins or so to work, then hose/pressure washer it if off if you can. If you can leave in the sun to dry off, as a PP has mentioned this be beneficial in killing off bacteria. Wear a mask and gloves as a precaution. If it doesn't obviously smell like pee chances are the rats haven't got to it. Normally rats will scent mark as they move around.

To op it is and I completely understand. I would be devastated if I had to bin all my xmas stuff.

I'll be reiterating much of what others say...

• there is a risk of disease from contact with rat urine, leptospira and hantaviruses being the main concerns.

• this isnt unique to rats - many other UK rodents are primary reservoirs of those diseases, and many other animals (notably, farm animals, squirrels and domestic dogs) are secondary carriers.

• the number of cases of leptospira are very small (about 50-100, and most don't progress to Weils). Most people who contract it are farm workers, sanitation workers and alike. Domestic cases do happen, but we're likely talking single digits.

• to contract leptospira, rat urine would need to enter your body through an open wound, or your mouth/eyes.

Gloves, a face mask and antibacterial cleaning products ought to do the job. The risk is not zero, but it is tiny. I wouldn't be considering throwing anything away unless it was meaningfully and visibly rat damaged and, even then, that's more due to "ick" than risk.

Doesn’t it come apart into a couple of sections ?

I hope the neighbours are dealing with their rat problem. Seems to be an issue with decking, yuck. Just had rats under my shed, our council have a pest control unit who were great.

I personally wouldn't get rid of anything unless it had been chewed a lot. I probably wouldn't even clean it on the off-chance a rat had been touching it, unless it smelled horrible or the cleaning was very simple and not time consuming.

The smell is very obvious if they have peed on it

OP, we had rats; in the attic and they made their way downstairs too.
Our amazing pest control man ( who works for Environmental Health) and often deals with business and hospitality venues, said the Leptospirosis risk is vanishingly small in domestic premises these days, and a dettol wipe-down is v sufficient. But he said that there is no way he would swim in UK rivers, where the risk is higher, ( though, also still rare).
He really knew his stuff. He treated the house, located entry points, sealed them, and we've never had them again. ( This was 3 years ago). He was v v knowledgeable.
I hope that reassures you a bit.
I'm sure you don't need to chuck everything out.

Firstly I'd send the cat in. If anything soft and unwashable has been peed on then the cat should be able to sniff it out. Unless you have a daft cat. Other stuff, wipe it or wash it. If not an option couldn't you put the tree outside somewhere sheltered?

Rat wee causes Weils disease, hantavirus and other nasties, so while OP should not go overboard with worry, this advice is not adequate. if you put a question into Google OP, you will get specific advice on how to clean things where possible. Its important to spray things first rather than pick them up, as some dried pee can still be contaminating and should not be allowed to get airborne. 🍀

I do appreciate too that it's sad to lose sentimental things. I lost a whole box of Christmas ornaments that belonged to my grandmother some years ago. I was sad, but you do get over it.

I've had to deal with this OP. Just look at each box and see if it has been affected. You won't know where you stand until you do. You might not have lost much at all. If luck is with you your cat may have kept their numbers down in your shed.

Some things you can just clean well and it will be fine. Other things not so much - if the tree is affected I suspect you will have to toss it out.

But even if so - yes, it really is a drag, but not the end of the world. There are cheap things you can do to make a nice Christmas, it's not all about the tree. You can start rebuilding your Christmas items a little at a time. Buy a small tabletop tree for this year for your own gift if you have to.(Or go to the woods and bring a little one home.) Decorate it with home made decorations. You can dry out orange slices or make salt dough which will be a nice activity for the weekend. If you can't afford a small tree, just make some decorations and use those around the house.

Take everything out, examine for signs of chewing, nesting or droppings - look like large brown pieces of rice.

If you've got signs of this, then its probably best to bin the decorations and spray the brooms.

Rats piss can harbour bacteria for a few weeks, especially if the area is damp & whilst Weil's disease is rare in the UK, if you aren't happy, then throwing it out is the best thing you can do.

Washing xmas decorations would v difficult, charity shops might have some?

Bin anything that’s been visible chewed or dirty and give the rest a good misting with dettol spray and you’ll be grand.

I live in the country and see rats all the time, It wouldn't occur to me to dump everything. What a waste! Give things a clean if you want, but as long as no-ones going to be licking your garlands (so to speak), there's zero reason not to hang them up. Just put on a pair of rubber gloves when handling them if you're really worried.

Which is in rat wee, apologies I should have said
Its just a possibility of a bit of rat wee which MAY carry diseases.
Either OP needs to clean it but if she isn't comfortable with the items even after that she will have to throw them
Not a "nightmare" though

@Hoppinggreen Its not, its just a possibility of a bit of rat wee

Whilst Weil's disease is rare, I wouldn't be risking anything that couldn't be thoroughly washed down, especially as the OP has children! https://www.healthline.com/health/weils-disease

It was quite funny, as it was a baby rat, it was small and actually quite cute to look at but any time we could see it we screamed and ran. In the end I said to DD, we can't let it move in here so I have to catch it, and when it sat on the sideboard looking at me, I just popped a jug on it and slid a lid underneath and carried it out at arms length

Its not, its just a possibility of a bit of rat wee
Not nice I appreciate but nothing too awful and not worth ruining your day/Christmas over

Surely dettol spray is effective?

Sunlight is the best and cheapest disinfectant! So if you’ve got a dry bright sunny day like it is here I’d put stuff outside for a good airing. Bin anything thats been visibly chewed or smells ratty!