Such animals as shall be found to have any infectious or contagious disease shall immediately be slaughtered by and at the expense of the importer or owner or held in strict quarantine, if the disease is curable, under rules adopted by the commissioner; provided that registered purebred bovine animals, reacting to the tuberculin or other approved test, but showing no marked physical indications of tuberculosis, may be retained by the importer or owner in quarantine and be subject to the provision of N.H. Rev. Stat. § 436:62-68.