Not sure if this has been mentioned as this thread is now quite extensive and the search function isn’t always the best. BA long haul aircraft are inspected by ‘Merlin’ sniffer dogs every three months, regardless of whether or not there have been reported cases.

Edit: Merlin Environmental is a company that provides sniffer dogs for the purpose of bed bug detection. They’re used by, amongst others, a number of hospitality and transport companies.