I was under the impression that Advocate was the only drug licensed as a preventative treatment, with Panacur being the preferred method of actually treating a confirmed infection.
I know Milbemax, if given monthly, gives "some" protection, but it isn't licensed for this.
I have had to go with taking my chances with Lungworm... we did try Advocate for 3 months, as there were several confirmed cases of Lungworm in the local area... but Honey was getting very itchy at the application site, and the reaction was intensifying each time, which was concerning...
This is, as I still understand, the best way to prevent lungworm. After nearly loosing Purdey to lungworm a few years ago, I would rather treat (more often in summer but not always monthly - less through the winter months) by appropriate products - her life has possibly already been shortened by the damage done to her heart & lungs, so take a chance with the medication TBH.
Lungworm is rife in our area, with new & unusual symptoms appearing all the time. Through my experience with Purdey, if you ask any number of vets their opinion or advice they would all vary in some way or another, with some still handing out incorrect advice - my vet seems pretty spot on with it all now & has taken part in a national survey investigating lungworm & the variation & differences in symptoms being presented.
The specialist advice at the time was that Lungworm was & still is a fairly new condition & vets are learning about it all the time - due to where we live, Purdey being a skillful scavenger & her not having any recurrence of the condition, is proof enough for me that the method I am using works, so choose to stick with it .........unless vets learn of a safer alternative or a way to eradicate the blighters