Platforms and chutes used for handling imported swine shall be cleaned and disinfected under APHIS supervision after being so used. The said swine shall not be unnecessarily moved over any highways nor allowed to come in contact with other swine, but shall be transferred from the conveyance to the quarantine grounds in boats, cars, or vehicles approved by the inspector in charge at the port of entry. Such cars, boats, or vehicles shall be cleaned and disinfected under APHIS supervision immediately after such use, by the carrier moving the same. The railway cars so used shall be either cars reserved for this exclusive use or box cars not otherwise employed in the transportation of swine or their fresh products. When movement of the aforesaid swine upon or across a public highway is unavoidable, it shall be under such careful supervision and restrictions as the inspector in charge at the port of entry and the local authorities may direct.