Perhaps you almost saw a dozen birds die this week, but before death they became sickly and were picked off by predators. Perhaps others died right out in the open and were dragged off by scavengers before you saw them.

A dozen dead battery farmed chickens, on the other hand, would go nowhere and could likely infect many other chickens before being discovered counted and disposed of by a farm worker.

When my bird watcher friend finds dead birds on her hikes, she inspects them, then if they show signs of infection she bags and labels them to send to a research station. She's amazing at spotting a small dead bird in tall grass and I wouldn't have spotted any of the ones she did on our last hike.

One way to think of it is that a plants most powerful immune system to prevent infection from spreading is that it doesn't have a circulatory system like ours. Moisture and nutrients go into the pumpkin, but as far as I know (not that I'm an expert) nothing goes the other way.

Also, the stem is probably woody and not even an open channel for that by the time the pumpkin is rotting.