Aside from removing the dead rat Emily there isn't a lot you can do apart from putting down traps or poison. Where are you in the UK, in an urban setup there are rats around most of the time folk just don't see them.

Perhaps there is a concern about the saftey aspect of eating produce grown where a dead rat has been.

I think personally I definitely wouldn't eat things grown in that bed raw.

Be carfeul handling the dead rat as well.

I reckon ordinary veg would be fine as you cook it in any case. If it was me I would just bash on as normal- we don't see what goes on in commercial fields! However no harm in avoiding salads this year if it worries you. Any danger would be from urine and droppings and both those would have disappeared by the time the crops have grown. Happy to be corrected on this - just my own opinion.

There's a saying in towns and cities - you're never more than 3 feet away from a rat, or several rats. They're everywhere, all the time, but when one dies in this way, that's when you notice them. Bait boxes around and about should help, but in reality, all kinds of creatures could be roaming through your veggies, doing their business as they go, and you'd not know. I'd remove the body, and, if it was partially rotted, some surrounding soil as well, and carry on as normal.

id wonder why it died out in the open as it probably has been killed with poisen . if yopu have pets this could well be a problem if they eat it . i wouldnt worry about the ground underneath thow . how many things do you think have died and rotted over the last 500,000,000 years or so . its natures way apart from the possabillity of poisen .

It's leptospirosis or Weil's Disease that you are worried about. As the bacteria do not have a waterproof membrane they must remain immersed in water to survive, and so are killed immediately their environment dries out. The inability to survive out of water is the single most important control factor in the natural environment, as it means they are unable to create infection risks from dry surfaces.