[Fleas on small mammals in the surrounding area of Erhai Lake].

OBJECTIVE: To investigate the distribution pattern, species diversity and community structure of fleas on small mammals in the surrounding area of Erhai Lake, and the relationship between fleas and their hosts. METHODS: Different geographical areas surrounding the Erhai Lake in Yunnan were selected as investigated spots. Small mammals were captured with baited cages. The cage-traps were examined and re-baited each morning. All fleas on the hosts were collected and identified. The richness (S), evenness (J'), diversity index (H'), dominance index (C'), total ectoparasite infestation rate (Rpt), total ectoparasite infestation index (Ipt), and constituent ratio (Cr) were used to measure the community structure. RESULTS: Altogether, 3,303 small mammals and 3,243 fleas were collected. From the 21 species of small mammal hosts, 13 species of fleas were identified. In southern area of the Lake, the species richness (21 species of small mammals & 12 species of fleas) was highest among the three selected areas. Seventeen species of small mammals and 8 species of fleas were found in eastern area, and only 13 species of small mammals and 7 species of fleas found in the west. This implied the probable influences of ecological environments on the fleas and their corresponding hosts. The community structure of fleas on small mammals was complex. The species diversity, species composition, community structure and distribution pattern of fleas were simultaneously influenced by the hosts' body surface microenvironment and the macroenvironment (habitat). CONCLUSION: The fleas are commonly distributed in small mammals in the areas and their communities are related to host species and the habitats.

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To understand the characteristics of community structure and spatial distribution of small mammals in agricultural area of Yunnan Province, a systematic investigation was carried out in 104 quadrats of 25 regions in Yunnan Province from August 2010 to April 2018 by rat trap night method. The spatial variation of community characteristics along environmental gradients was analyzed by community ecological indicators. The results showed that a total of 3240 small mammals were captured and cold be classified into 42 species in 21 genera, 9 families, and 4 orders. The largest number of small mammal was rodents, dominated by Apodemus chevrieri and Rattus tanezumi. The 25 regions were clustered into three classes. The altitudinal distribution of small mammals was similar to the latitudinal distribution in agricultural areas. The number of species was relatively less in the low latitude and altitude range, with Rattus spp. and Mus spp. as the dominant species. In the high latitude and altitude region, the dominant species changed into Apodemus, Niviventer and Eothenomys. With the increases of altitude, the diversity index showed unimodal distribution, with the highe-st species diversity occurred in the mid-altitude area. The diversity index of small mammal showed the "V" type pattern in longitude, being the highest in the 98°-99° E gra-dient zone. At the latitude level, it showed an overall upward trend from south to north. Results from the GAM analysis showed that the degree of influence on the small animals in the agricultural area was in order of longitude, altitude and latitude. The similarity analysis in the composition of small mammals showed that the moderate similarity occurred in the adjacent gradient zone, and the highest similarity occurred in middle altitude zone, middle latitude zone, and low longitude zone. The farther the distance between different gradient zones, the lower the similarity of community structure. There was high spatial heterogeneity in different dimensions of small mammals' community structure in Yunnan Province. The geographical distribution trend of species diversity showed different distribution patterns across environmental gradients.

Phylogenetic analysis of Bartonella detected in rodent fleas in Yunnan, China.

Previous studies have demonstrated a diversity of Bartonella spp. in rodent populations in Yunnan Province, China. Although Bartonella spp. have been isolated from cat fleas and cattle ticks collected from their animal hosts, little is known about Bartonella carried by rodent fleas. In this study, Bartonella DNA was detected by polymerase chain reaction (PCR) in two of five species of rodent fleas. These included Xenopsylla cheopis and Ctenophthalmus lushuiensis, which were collected from Rattus tanezumi flavipectus and from the nests of voles, respectively, during 1997 from two sites in western Yunnan Province, China. Sequence analysis of the Bartonella citrate synthase gene (gltA) amplicons obtained from six of 65 grouped flea samples showed that Bartonella genetic variants were clustered in four groups. One from Xenopsylla cheopis was identical to Bartonella tribocorum, whereas the other three genotypes from Ctenophthalmus lushuiensis were related to the vole-associated Bartonella isolates and cat-associated Bartonella clarridgeiae. This is the first detection of this Bartonella variant from fleas in China. Therefore, further investigations are needed to clarify the distribution of Bartonella in rodents and their ectoparasites in China to define the role of these arthropods in the transmission routes of Bartonella.

A new hantavirus from the stripe-backed shrew (Sorex cylindricauda) in the People's Republic of China.

Inspired by the recent discovery of genetically distinct hantaviruses from insectivore species worldwide, we performed a small-scale search for insectivore-borne hantaviruses. In this paper, we report the discovery of a new hantavirus, which was designated the Qian Hu Shan virus (QHSV). This virus was detected in the lung tissues of three stripe-backed shrews (Sorex cylindricauda), which were captured in the Yunnan Province, China. The full-length S genomic segment of the representative QHSV strain YN05-284 was 1661 nucleotides and is predicted to encode a nucleocapsid protein of 429 amino acids that starts at nucleotide position 48. It exhibited the highest similarity with other Sorex-related hantaviruses, with 68.1%-72.8% nucleotide and 71.9%-84.4% amino acid sequence identities. An analysis of a 1430-nucleotide region of the partial M segment exhibited approximately 54.4%-79.5% nucleotide and 43.2%-90.8% amino acid sequence identities to other hantaviruses. A comparison of a 432-nucleotide region of the L segment also showed similar degrees of identity, with 68.9%-78.4% nucleotide and 71.1%-93.8% amino acid sequence identities to other hantaviruses. Phylogenetic analyses using Bayesian methods indicated that QHSV shared the most recent common ancestor with other Sorex-related hantaviruses. The host was identified using a morphological assessment and verified using mitochondrial cytochrome b (mt-Cyt b) gene sequencing. A pair-wise comparison of the 1140-nucleotide mt-Cyt b gene sequence from the host demonstrated that the host was close to S. cylindricauda from Nepal with 94.3% identity. The virus-host association tanglegram, which was constructed using the Dendroscope software, indicated that the QHSV phylogeny and the host phylogeny were approximately matched, which suggests no evidence of host switching for QHSV. Our results contribute to a wider viewpoint regarding the heterogeneity of viruses that infect shrews.

[Ecological-geographic landscapes of natural plague foci in China VI. Biological characteristics of natural vectors of Yesinia pestis].

OBJECTIVE: To characterize the biological characteristics of natural vectors of Yersinia (Y.) pestis in China. METHODS: Species and genera of natural vectors of Y. pestis in China and their faunal distribution were characterized with modern insect taxonomic techniques. The ecological roles of natural vectors of Y. pestis in natural plague foci were determined according to insect ecological experiments. RESULTS: There were 63 species of natural vectors of Y. pestis including 28 major reservoirs and 35 secondary ones. CONCLUSION: The biology characteristics of major vectors on Y. pestis and their roles in natural plague foci were defined.

[Ecological-geographic landscapes of natural plague foci in China VII. Typing of natural plague foci].

OBJECTIVE: To group and characterize natural plague foci in China. METHODS: A novel two-class typing method as well as a three-indication nomenclature method were established to group and characterize the natural plague foci, on the basis of eco-geographical landscapes of plague foci, genetics of Yersinia pestis, zoology of rodent reservoirs and the entomology of flea vectors. RESULTS: A total of 12 distinct natural plague foci (including 19 subtypes) as well as their biological features were characterized. CONCLUSION: Natural plague foci in China were grouped and characterized in this study.

Genetic analysis of a hantavirus strain carried by Niviventer confucianus in Yunnan province, China.

Hantavirus genome sequences were recovered from lung tissues of Chinese white-bellied rats (Niviventer confucianus) captured in Yunnan province, China. Pairwise comparison of the nucleotide and deduced amino acid sequences of the entire S and partial M and L segments indicated that the newly discovered virus strain, which was designated as strain YN509, was very different from other rodent-borne hantaviruses. Phylogenetic analysis showed that the new strain fit into a clade containing Da Bie Shan virus (DBSV) (also carried by N. confucianus), which is mainly found in Anhui Province in mainland China. Strain YN509 appears to be in a sister taxa of the DBSV group described previously. These data suggest that strain YN509 is a new subtype of DBSV, which appears to be widely distributed in China with a higher genetic diversity than expected.

[Identification of Anaplasma phagocytophilum in small mammals from Hengduan Mountains of Southwest China].

OBJECTIVE: To investigate the prevalence of Anaplasma phagocytophilum in small mammals from the forest area of Hengduan Mountains in southwestern China. METHODS: Small mammals captured from Gaoligong and Xianggelila mountainous area of Yunnan province were detected by PCR amplification. The sequences of 16S rRNA and Msp4 gene fragments from positive samples were compared with corresponding sequences deposited in GenBank. RESULTS: A total number of 436 small animals, which belongs to 5 orders 18 genera 35 species were tested, 32 (7.34%) were positive in 6 genera 11 species. There were 8.64% (26/301) positive in 25 species at Goligong mountainous areas, and 4.44% (6/135) were positive in 19 species at the Xianggelila mountainous areas. Positive small mammals were most rodents. The nucleotide sequences of A.phagocytophilum 16S rRNA gene amplified from small mammals varied from 99% - 100% and were 99% - 100% similar with the corresponding segments of A. phagocytophilum from Jilin deposited in GeneBank. The sequences of A. phagocytophilum Msp4 gene showed that there was 95% - 97% similarity with the corresponding sequences registered in GenBank. CONCLUSION: A. phagocytophilum was firstly identified in 6 genera 11 species small mammals from a forest area of Hengduan Mountainous areas in southwestern China. Rodents might serve as the primary hosts indicating the potential risk to the domestic animals and human beings in this area.

Isolation and characterization of the full coding sequence of a novel densovirus from the mosquito Culex pipiens pallens.

During an investigation of arboviruses in China, a novel densovirus (DNV) was isolated from the adult female Culex pipiens pallens. The virus, designated Culex pipiens pallens densovirus (CppDNV), caused cytopathic effect in C6/36 cells. The virus particles were icosahedral, non-enveloped and had a mean diameter of 24 nm. The complete coding region of CppDNV was found to be 3335 nt and it contained three open reading frames (ORFs). CppDNV shares 82-93 % identical nucleotides with isolates of the Aedes albopictus densovirus [isolates AalDNV-1, AalDNV-2 (C6/36 DNV) and AalDNV-3], Aedes aegypti densovirus (AaeDNV) and Haemagogus equines densovirus (HeDNV). The nucleotide sequence identity among CppDNV isolates exceeds 98 %. Phylogenetic trees based on non-structural (NS1 and NS2) and capsid (VP) genes show that CppDNV clustered with the species AaeDNV and represents a novel variant of this species within the genus Brevidensovirus.

[Study on the prevalence of Bartonella species in rodent hosts from different environmental areas in Yunnan].

OBJECTIVE: To investigate Bartonella infections in small mammalian reservoir hosts from different environments and types of climate in Yunnan. METHODS: Femoral blood samples were collected from the anesthetic captured animals from five counties including three types of climate. All isolates were grown on brain and heart infusion agar plates containing 5% defibrinated rabbit blood. The agar plates were incubated at 35 degrees C in a humidified with 5% CO2 environment for at least 4 weeks. Bartonella-like isolates were confirmed by the polymerase chain reaction and visualizing the target gene fragment by gel electrophoresis. RESULTS: Bartonella species were isolated from 69 of 176 small animals including 4 species of 3 genera from 4 counties and the total prevalence in rodents was 39.2%. The maximal prevalence was 42.0% of Rattus tanezumi flavipectus usually inhabiting indoors and courtyard and contacting closely to human. Moreover, Bartonella isolates were obtained from Rattus noruegicus, Eothenomys miletus and Mus pahari. Life environments of captured animals involved indoors, courtyard, brush and forest in mountain. CONCLUSION: The finding in this study suggested the characteristic of diversity of Bartonella infections in rodent hosts in southern China included Bartonella species parasiting in a wide range of animal hosts in different environments as well as climate types. Further investigations were needed in different areas in China to confirm more mammalian reservoir hosts with Bartonella infections.