Gooseberry pruning

http://apps.rhs.org.uk/advicesearch/Profile.aspx?pid=332

http://www.rhs.org.uk/Video/Gooseberry-pruning

Couple of useful links - yes you can prune now.  And I think it's OK to take some branches out all the way.

3 steps to pruning...1 cut out any diseased or dead wood
                                2 cut out any overlapping branches
                                3 open up the middle of the bush so that the finished item resembles a wine glass.

Hi Mike,
You can use the healthier pruning's as cuttings  if you want to increase your stock
http://apps.rhs.org.uk/advicesearch/profile.aspx?PID=387

Dmg

Are you sure it's mildew?

When gooseberry bushes become a few years old they often have lichen on them, often the same colour as mildew but it doesn't wipe off. Lichen has darker, greyer areas in it. No problems with lichen although in general it indicates the wood is old and maybe time to prune it out.

Good advice in previous posts. Gooseberries fruit on wood produced in the previous year and also earlier years. The older the wood gets the less fruit it will produce. Prune out any stems which are touching (or early touching) the ground. Stems near the ground attract pests and diseases and are best shortened to an upward facing bud.