Yes, thank you - I could have phrased that more accurately.
Nothing can truly prevent a dog (with outdoor access) from coming across/ingesting the infective L3 stage of the A.vasorum life cycle which is found mainly slugs and snails.
Similarly we can't prevent fleas or ticks jumping onto a pet, but can routinely treat to reduce the morbidity these parasites cause.
A couple of treatment regimes have a pharmaceutical licence (in the UK) for prevention of patent lung worm infection (infection causing symptoms). Others are licenced for treatment only and will reduce and control the burden if used routinely.
Some people will prefer to treat fleas and ticks when they see them rather than use routine treatments regularly. With lungworm, it's not as easy to see if your pet is infected. I believe faecal tests tend to rely on detecting excreted L1 larvae (shed in in heavy infestation) or DNA detection. The eggs are not passed in faeces.
It's a serious parasite and can cause death or serious bleeding. I find some owners are not as aware of it in the same way as ticks or fleas.
I am worried I will be seeing more cases given the mild winter and wet summer ...so just wanted to raise awareness.