Observations on Wild Rats in England, with an account of their Ecto- and Endoparasites

Abstract

1. Attempts to secure a micro-organism which could induce abortion or sterility in wild rats and which might be used in an anti-rat campaign, more especially when plague threatens a community, have not been successful.2. An account, however, is given of certain micro-organisms producing pathological conditions in the genito-urinary tract of wild rats.3. A routine determination of rat parasites including ecto-parasites, helminths, intestinal protozoa and haematozoa has been undertaken.4. It has led to the discovery of a new species of Hymenolepis and has shown that Heligmosomum braziliense is present in rats in England. It has also demonstrated the occurrence of haemogregarines in the leucocytes of black rats in this country.5. Work has been done on the incidence of Leptospira icterohaemorrhagiae in Rattus norvegicus and Rattus rattus in England and on the mechanism of its transmission.6. It has been shown that apparently the guinea pig may act as a carrier of the Leptospira without exhibiting any marked symptoms of the disease which the latter produces. There is also some evidence to prove that infection may take place through the alimentary tract.7. The Leptospira was successfully and easily cultivated in Wenyon's modification of the Noguchi method but in large measure lost its virulence as the result of repeated subcultures. Even after a year, however, it was still capable of producing characteristic symptoms in the guinea pig.8. General pathological conditions occurring in wild rats have been recorded.9. A few observations have been made on the seasonal incidence of pregnancy in wild rats.