Just returned yesterday from Cambodia and Laos. The day before yesterday, I crossed the Lao/China border at Mohan, and have a question.

On the Chinese border there is a police complex, and upon entry was told to close the windows. This was because some type of disinfectant was sprayed on it. Upon leaving the bus, a guy came on the bus with a tank and a bug spray device and wetted the floors with it.

Made me wonder what they were spraying for? Bugs is the only thing I could think of. However, since it is the same terrain, wouldn't there be bugs on both sides of the border? Mosquitoes?

We had to get off the bus with our stuff and was gruffly told to open our bags, and a second guy with gloves opened our bags and went through everything. Make sure you don't have any roaches in your bag you forgot about or anything else the popo might not want to see.

What was that stuff?

Unlikely to be bugs, more something you might be having on your shoes or the bus on its tires. I do not know what it was, but I think it might be a livestock disease, maybe foot-and-mouth.

This would also explain the thorough bag searches: not looking for contraband, but meat products. Usually the bags just go through x-ray, but that would not pick up foodstuffs.