Sharon, I asked a friend of ours in the village (Mas de Barberans - Montsia) about this problem and she hadn't heard of it.  She has 2 very much loved house dogs and her husband has a few very well looked after hunting dogs that sleep outside.  They have them inoculated against heart worm, the vet comes out to them between April & Nov.  Maybe it would be worth talking to a local vet to get an accurate picture.