Pesticide spraying on int'l flights

[Boeing4ever]

I have a question to you all down under:

I saw a documentary film here in Italy about Lufthansa's round-the-world cargo operations with the MD-11F and on its arrival in New Zealand, an official of some sort came on board and sprayed the entire cabin + cockpit with pesticide using spray cans, and the pilots had to remain on board and endure all that. The commentator said that all flights from international destinations in NZ and Australia had to be sprayed the moment they arrive.

I find it somewhat hard to believe that passengers would have to endure this - what about people with allergies or simply people that are sensitive to chemicals?

So my question is: did the commentator mean all cargo flights or really ALL flights? And also, what is the reason for the spraying? Is Australia/NZ still vulnerable to deseases/sicknesses that Europeans aren't? Or do insects from other parts of the world pose a threat to your insects or something?

Thanks, Marco

P.S.: Could someone please give me links to both Australian and NZ aviation forums? I can't seem to fing any through Google.