The Fleas Common on Rats in Different Parts of the World and the Readiness with which they Bite Man

Abstract

(1) As far as is at present known, the great majority of the fleas infesting Mus rattus and Mus decumanus in different parts of the world, belong to either the species Xenopsylla cheopis, Ceratophyllus fasciatus, Ceratophyllus anisus, Ctenopsylla musculi or Ctenophthalmus agyrtes or are comprised of some admixture of these five species.(2) Xenopsylla cheopis is the most prevalent in the tropics and sub-tropical regions and often occurs there to the almost complete exclusion of other species. It is common during summer and autumn in some of the warmer parts of the temperate zone, more especially in ports which have maritime intercourse with the tropics.(3) In the cooler regions Ceratophyllus fasciatus is the most universally distributed flea and is associated with more or less of Ctenopsylla musculi and Ctenophthalmus agyrtes according to the locality and the habitat of the particular rats.(4) In Japan Ceratophyllus fasciatus is replaced by Ceratophyllus anisus, a closely allied species.(5) The numerous other fleas which have been captured off rats are only occasional visitors.(6) Ceratophyllus fasciatus, like Xenopsylla cheopis, readily bites man. Out of 517 experiments 308 fed, or 59% were positive. In 101 experiments, under identical circumstances with a rat, 59, or 58.4% of the fleas fed.(7) The experiments with Ceratophyllus fasciatus were made upon eight persons and evidence was obtained of preference on the part of the insects for particular individuals.(8) 111 experiments were made with 46 specimens of Ctenopsylla musculi; only 4 fed=3.6% whereas 9 out of 11 fed on a mouse.(9) 68 specimens of Ctenophthalmus agyrtes were tried, in some cases upon three persons. None fed, whereas 11 out of 19 of the same fleas fed on a rat under identical conditions.