Vets can be a problem. I find, even with experienced ones, I have to call them to heel from time to time with reminders !
You have to educate them. Start off with the 'longer seasons just once a year' theme, go on to 'only use external preparations suitable for cats because Basenjis clean themselves like felines' and get them to read up specifics on-line.
The worst case of ignorance I have ever come across was a US military Vet, stationed in Germany. He was unaware that Basenji boys carry fore and after, not side by side as other breeds.
He insisted on castrating a perfectly normal, healthy young male on the basis he mustn't be allowed to pass on such a deformity ! The UK Breeder was given a hard time by the new owner of the pup, but enough of us had seen the boy before he was shipped out to a US serviceman stationed in Germany. . .