Plague: Modern Preventive Measures in Ships and Ports: (Section of Tropical Diseases and Parasitology)

Maritime quarantine, introduced in the fourteenth century in an endeavour to prevent the spread of plague. Though the system failed to achieve its object, and was expensive and restrictive to sea-borne commerce, it survived for over 500 years, presumably because, in the absence of knowledge of the aetiology of plague, no method of procedure more likely to be successful could be devised. This country acknowledged the failure of quarantine as a preventive measure in the middle of last century, and substituted the medical inspection of ships on arrival, though the last Quarantine Act was not repealed till 1896. Nevertheless it was not till the discovery of the rôle of the rat and the rat-flea in the spread of plague that it was possible to establish plague-preventive measures on a sound scientific basis.It is now recognized that a Port Health Authority must not only take steps to detect plague, human or rodent, afloat or ashore, at the earliest possible moment, but must eliminate conditions in ships and in shore premises which are conducive to the development of an epizoötic. Though here, and in other countries with an enlightened Public Health Administration, practice has long been ahead of legislation, the International Sanitary Convention of 1926 has now established throughout the world a large measure of uniformity in measures designed to prevent the spread of the more dangerous epidemic diseases by overseas trade, and the Port Sanitary Regulations 1933 have brought quarantine legislation in this country up to date.For the detection of plague every ship arriving from a plague-infected port is medically inspected on arrival, but even if there is no evidence of plague-infection on board, such ships are examined daily by a rat-officer until the discharge of cargo is complete. Dead rats found and live rats trapped are bacteriologically examined. If a rat is reported to be infected the vessel is fumigated at once. The discharge of cargo is then continued under supervision, and when the ship is empty she is fumigated again. Shore premises, particularly those in the immediate vicinity of the berths of ships from plague-infected ports, are systematically searched for dead rats, and live rats are trapped. If evidence of plague-infection is found, energetic measures of rat destruction are at once instituted over a wide area.The International Sanitary Convention requires all foreign-going ships to be inspected every six months as to the number of rats on board. If a ship is not so maintained as to keep the rat population down to a minimum she must be deratized.If, after deratization, ships are to remain free from rats, they must be rat-proofed. Similarly ashore, rat-proofing is the only rat-repressive measure of permanent value.The measures usually adopted to prevent the passage of rats between ships and shore are of limited value.Finally, a rat-flea survey is of value in estimating the susceptibility of a port to infection.