Bhutan isn’t the first country to do it. The Netherlands achieved it a few years ago, through their CNVR programme carried out through 200 over years: https://everydogmatters.eu/how-did-the-netherlands-manage-to-become-the-first-country-with-no-stray-dogs/
Excerpts:
After years of being involved in a humane animal welfare programme, Bhutan has announced that all of its street dogs have been fully sterilised and vaccinated
According to DownToEarth, this comes 14 years after Humane Society International (HSI) began a dog population control initiative in 2009 to neuter and vaccinate Bhutan’s street dog population.
This incredible accomplishment was announced by Bhutanese Prime Minister Lotay Tshering, who spoke at the conclusion of the National Dog Population Management and Rabies Control Project in Thimpu, Bhutan’s capital city.
He said that over 150,000 street dogs were sterilised and vaccinated, and around 32,000 domesticated dogs had also been microchipped.
Photo credit: World Animal News