ABSTRACT
Objective To explore the relationship between wild rodent plague and human in wild rodent plague foci of the northwestern area in Yunnan to probe the possible transmission mechanism of wild rodent plague to human. Methods Data of component ratio of rodents and fleas was collected in different areas from 1985 - 1995. Activities and habits of residents regarding the way they keep cats and dogs and parasitic fleas and free fleas indoor were investigated, the dog serum was collected for detecting F1 antibody. Results Eothenomys miletus were main rodents in farmland and shrub, accounting for 48.00% (4753/9902) and 54.50% (4282/7857), Apodemus chevrieri were main rodents in garden, being 50.47% (1332/2639). The component ratio of Neopsylla specialis specialis was 13.31%(229/1720), 12.31%(1678/13 739) and 10.87%(957/8802) respectively in garden, farmland and shrub, higher than in indoor. The component ratio of Frantcpsylla spodix was 39.88% (686/1720), the highest in garden. Thirty-two per cent (32/100) of residents kept cats,in which 63% (20/32) with cat fleas, 68% (68/100) of villages kept dogs, in which 76%(52/68) with fleas. Eighteen parasitic fleas were caught from 43 dogs with a flea index of 0.119 and a rate for fleas of 11.63%, 7 pulex were collected from 17 indoor. Forty-three blood serum samples were obtained from dogs, among which 3 were positive blood serum. Conclusions Residents touch affected animals or media in different situations. The possibility of transmission for wild rodent plague to human exists in loci in a chain of wild rodent plague → fleas or predation → homebred animal plague (cats or dogs) →touching or respiratory → human.
ABSTRACT
Objective To explore the mutation and evolution of Yersiniapestis(Y. pestis) from the point of codon and 16S-ribosome. Methods Codon preference and 16S-ribosome of Y. pestis were analyzed by bioinformatics. Results Similar codon preference was found among 4 PCD1 Y. pestis, of the 3 old Y. pestis the codon preference between PMT1 and PCD1 was similar. There were some differences between PCD1, PCP1 and Yunnan 6 kb plasmid. Through the analysis of 16S-ribosome, the sequences were found similar in 11 strains of Y. pestis,Yersinia pseudotuberculosis was very close to Y. pestis, with only one nucleotide difference, mutated G-T, and corresponding amino acid methionine (M)-isoleucine (I). There were some differences in sequences of 16S-ribosome in Y. pestis, Escherichia coli and Pulex irritans. Conclusions The time for Y. pestis to obtain PCP1 is later than PMT1 does, in other words, the affinity of Y. pestis with PMT1 was closer than PCP1 with 6 kb plasmid;alteration of 16S-ribosomal nucleotide sites may cause changes in function and structure of 16S rRNA. The lower similarity between 16S-ribosomal sequences of Y. pestis and Pulex irritans indicates the time for co-evolution is very short,and the late emergence of Y. pestis.