Question

how was rat hunt started and why

Answer 1

Rat hunt started in France because a epidemic caused by rat. the rat cause a disease called plegue so the rat hunt started in France

Answer 2

The French sought to change the infrastructure and built a modern Hanoi while the native quarter of Saigon was dirty
The modern city of Hanoi had well laid out sewer system.So the the refuse from this part of the city either drained out in the river or overflowed in the streets during heavy rainfall
So the sewers began to be a good breeding grounds for the rats
Irritated by the frequent occurrence of mice in the houses they asked the poor Vietnamese to clean the sewer and kill the rats . Bounty was paid when the tail of the rat was given as proof
This started the rat hunt in 1903