Rat control in a plague outbreak in Malta

Abstract

1. Methods of rat destruction devised in the United Kingdom during the war were applied to combat plague in Malta.2. The species were Rattus norvegicus Berkenhout, and R. rattus L. The first is the more common and played an important part in carrying plague.3. In the last 7 months of 1945, 75 cases of plague were diagnosed. In 1946, 5 cases occurred. A marked fall in the incidence of flea-borne (murine) typhus occurred in 1946.4. Systematic rat destruction began at the end of August 1945. The method was prebaiting, followed by poisoning with baits and poisons of known efficacy and change of both bait and poison for follow-up treatments. For this purpose a large organization in which the Navy, Army and R.A.F. took part, as well as the Medical and Health Department, was set up under unified control. This made it possible for large blocks and areas to be treated as a whole and within a short space of time.5. Evidence is given that the degree of clearance achieved by these methods was satisfactory. Comparison of the figures of baiting points visited in first and second baiting treatments suggests, in most instances, a satisfactory kill; this is confirmed by the fact that third treatments, when they were carried out, were found to be unnecessary. Reports from the public and house-to-house inquiry also suggest a very great reduction in rat population.6. In January 1947, 9 tests for reinfestation were carried out in areas which had been treated between 6 and 17 months before. These tests indicated that few or no rats were present. It is therefore suggested that not only had a good initial clearance been achieved but that the effect was a lasting one.The author is indebted to Mr W. McA. Gracie, Director of Infestation Control, who also visited Malta in 1945, for making possible the publication of this paper; to Dr A. C. Briffa, Deputy Chief Government Medical Officer, and Mr Paul Cauchi, Rodent Control Officer, for answering many involved questions by post and for carrying out tests of reinfestation; and to Mr A. H. Bathard, formerly officer in charge of the R.A.M.C. Sanitary Section, Malta, for help in analysing the records. Thanks are also due to A. G. Jenson, F.R.I.B.A., for drawing the map and the figures.