Good question, and one I’ve often posed to Italians myself. But both my wife (the editor) and the writer of the article seem to believe that a ‘topo’ is a ‘topo’ no matter what we English-speakers might think, horrible things, no matter if they’re large and live in drains or small and live in holes in the skirting board.
‘Topolino’ (Mickey Mouse) is clearly a ‘topo’, but then so is the rat in the picture in our article.
Go figure.
Incidentally, Italians don’t seem to distinguish between monkeys and apes. You wouldn’t believe the time I’ve wasted trying to explain…