Back in 1939, the Nazis were not the only thing sweeping through Europe. There was also a whole outbreak of the rabies epidemic being carried by red foxes. The disease was moving rapidly southward and westward every year by several dozen kilometers. And it was going through country after country.
Given what was going on with World War II, not many countries had time to deal with the disease, which meant by 1967 it was a huge problem and had reached Switzerland. Rabies is a dangerous disease that targets the brain if untreated, infected people nearly always die. This meant that something had to be done, and the usual methods of trapping the foxes were not working. There were just too many animals roaming the forests with the disease, it would be impossible to hunt them all down. So a plan was created to set up a way to vaccinate them.
Vaccinating wild animals was a completely new concept that the Americans had been putting forward, but capturing animals and immunizing them by hand was proving very time consuming and also costly. So scientists figured out a way to allow wild animals to vaccinate themselves, first they tried adapting popular traps to shoot the vaccines instead of cyanide – but this failed.
So research was changed to create edible vaccines that could be hidden in a bait. By 1971, laboratories had invented an oral solution that could vaccine animals from rabies. Now they just needed the bait: they tried and tested everything from biscuits to sausages to eggs. But of course, they finally decided the best bait would be a disembodied chicken head: perfect for tracking a fox.
From 1979 to 1984, chicken heads would rain down on the Swiss countryside. In total over 52,000 heads were dropped, and wherever they did rabies disappeared. And then every European country decided to participate, millions of chicken heads were dropped, and by 1995 Europe was barely seeing any cases of rabies.