Usually the result of water getting into the vacuum. Either the components weren't completely dry before reinserted them or it got wet before you acquired it.   

I’d suggest washing the filter, dismantling the parts and leaving everything to dry for about a day or more. 

Use the Guides and manuals link on their Cleaning the filter(s) on your cordless vacuum cleaner post. Their diagnostic site provides a step by step cleaning 

Hey @Justin - If you’re stuck, here’s a playlist for their filter washing - YouTube - Playlist. 

Evening jayjay

Iv washed the filter fully untill it smells clean and no dogs smell..but as soon as I refit the filter it still smells like is from inside motor cage..iv ordered a new one and see how that goes..thanks for the advice 

Fitter a new dyson filter and it still smells off wet dog even more when you run it at max speed and it warms up ..smells better when I give it a few sprays off dettol antibacterial..full strip down later in the week..will keep you posted..

If it’s still there after a thorough wash, you’ll have to buy a new one!!