Abstract: Rattus norvegicus may be as the reservoir host of plague in some domestic plague foci of Yunnan province, and some of its ectoparasite species may be the potential vectors of human diseases. To understand the ectoparasite communities in a population of R. norvegicus in the surrounding areas of Erhai Lake and the potential medical and veterinary importance of these ectoparasites are described. Ectoparasite communities of 431 rats of R. norvegicus were studied by using Mann-Whitney U-tests and Spearman correlation analysis, which were sampled in the surrounding areas of Erhai Lake (a famous fresh water lake in Southwestern China) in Yunnan in 2003 to 2004. The constituent ratio (C), prevalence (P) and average ectoparasite abundance (A) were used to test prevalence and density of ectoparasites. The surveyed areas were located in the wild rodenttype plague focus, one of the 11 known plague foci in China and also an important focus of both scrub typhus and epidemic hemorrhagic fever (EHF). The results indicated that a high proportion (71%, 307 individuals) of the sampled 431 rats was found to be infested with ectoparasites. A total of 47 ectoparasite species, including 23 species of chigger mites, 16 species of mesostigmatid (gamasid) mites, 6 species of fleas and 2 species of sucking lice were collected from R. norvegicus. Within this ectoparasite complex, 16 species had previously been reported to be vectors of human disease agents. The results suggest that there is very high species diversity of ectoparasites of R. norvegicus.

Key words: Rattus norvegicus, ectoparasite, community composition, Erhai Lake, China