Why am I still finding fleas on my dog after lots of treatment?

[Watdidusay]

Dog has had a one spot treatment followed by 3 months of simparica trio.

House has been bug bombed 3 months ago. No carpets or rugs in the house and never saw any signs of fleas in the house at any stage but treated regardless.
Carpet additionally treated, everything hot washed etc.

We've only ever seen 3 fleas in 4 months, all on the dog and only one at a time.

Dog has no symptoms but I am still finding random fleas on her months later. They're definitely fleas.

No other pets in the house or in contact with her.

Should I just keep fumigating? I don't understand why the treatments don't seem to be working.

Vet nurse here.
Simp-Trio seems to be one of the much better products , are you giving it every 4th week?
How effective is the flea bomb compared to a spray such as rip or indorex ,you shouldn't need to do either often, some sprays say to just use once in a year I'm not familiar with flea bombs?
Are you certain dog sees no other dogs ?
Are you visiting a house with cats ?
Is it possible that you are visiting a property with a flea infestation?
Do you know it can take 3-6 months to get on top of a flea infestation, 95% of the fleas are in the environment and nothing kills them in the pupae stage so if your initial problem was quite bad you maybe on the very tail end of it now.
When a treated dog picks up a random flea from anywhere, with an efficient product you will not get another infestation because the flea will die.
Have you let the dog move around the house? This will maximise efficacy of product as opposed to containing to a smaller area.
Is the simp-trio the correct strength for your dogs weight?
I hope this may help, you can always pick your vet nurses brain, they can pick a vets brain too !
Fleas are persistent little buggers!

I spent months with Indorex, clean, hoover. Spray wait L, comb cats - on repeat. I during this time the cats were restricted to front room and hallway. Easier to manage

Thanks for all that.

Yes it's very prescribed for her weight (she weighs on the low end of the range for the dose).

She's taking the whole dose on the 20th of the month every month.

There was never a big problem that we could tell - we've only seen 3 fleas in 4 months. No droppings. We've never seen a flea in the house aside from on her. She has no itch at the moment.

Absolutely no contact with any other animals and doesn't visit other properties. Moves freely around the house.

Doesn't make sense to me and I'm concerned she's got some rare fleas that are resistant to simparica.

Does she go for walks in parks where other dogs visit?
even if she doesn’t interact with the dogs, she can pick up fleas from the ground. And the active treatment will take care of the fleas.

You’d have way more fleas than that if that were the case as they multiply quickly. The eggs drop and lay dormant for up to a year I believe and hatch into larvae when they sense movement. What you will be seeing is baby fleas who will die on their first bite as long as you keep up the simbarica. It takes a while but those new fleas won’t reach breeding stage and eventually they stop appearing. We had an infestation two years ago and in 20 years of having dogs we’ve never had one before but I didn’t realise they’d become resistant to the frontline I was using. Switching to simbarica and treating carpets and soft furnishings with indorex cleared it up over a period of a few months.

Well the fleas we have seen were quite large - definitely fleas but I'm not sure how big the babies tend to be! These were an about 1.5mm long and plump

Not the park no. She walks on pavement. She sits the back garden but isn't in direct contact with other animals. Other animals obviously come into the garden though eg cats from time to time, and we have seen the odd hedgehog over the years.