Rabbit populations go in cycles because the myx spreads more virulently when the population density gets above a certain level. A similar effect can be seen in grouse populations with a (natural) parasite affecting those. Then there are food availability issues as mentioned above. There are indeed very few rabbits to be had at the moment, as a friend of mine who shoots them to eat has noted, he got none at all last year.

Rabbits used to be very common (and native) in Spain, and the myx has made them permanently rare, which is a contributor to why the Iberian lynx has become so very rare, being a rabbit specialist. I'm not sure why it has been a permanent population suppressant in Spain when it runs in cycles in Britain.