Zoonotic pathogens identified in rodents and shrews from four provinces, China, 2015-2022.

Rodents and shrews are major reservoirs of various pathogens that are related to zoonotic infectious diseases. The purpose of this study was to investigate co-infections of zoonotic pathogens in rodents and shrews trapped in four provinces of China. We sampled different rodent and shrew communities within and around human settlements in four provinces of China and characterised several important zoonotic viral, bacterial, and parasitic pathogens by PCR methods and phylogenetic analysis. A total of 864 rodents and shrews belonging to 24 and 13 species from RODENTIA and EULIPOTYPHLA orders were captured, respectively. For viral pathogens, two species of hantavirus (Hantaan orthohantavirus and Caobang orthohantavirus) were identified in 3.47% of rodents and shrews. The overall prevalence of Bartonella spp., Anaplasmataceae, Babesia spp., Leptospira spp., Spotted fever group Rickettsiae, Borrelia spp., and Coxiella burnetii were 31.25%, 8.91%, 4.17%, 3.94%, 3.59%, 3.47%, and 0.58%, respectively. Furthermore, the highest co-infection status of three pathogens was observed among Bartonella spp., Leptospira spp., and Anaplasmataceae with a co-infection rate of 0.46%. Our results suggested that species distribution and co-infections of zoonotic pathogens were prevalent in rodents and shrews, highlighting the necessity of active surveillance for zoonotic pathogens in wild mammals in wider regions.

Metavirome of 31 tick species provides a compendium of 1,801 RNA virus genomes.

The increasing prevalence and expanding distribution of tick-borne viruses globally have raised health concerns, but the full repertoire of the tick virome has not been assessed. We sequenced the meta-transcriptomes of 31 different tick species in the Ixodidae and Argasidae families from across mainland China, and identified 724 RNA viruses with distinctive virome compositions among genera. A total of 1,801 assembled and complete or nearly complete viral genomes revealed an extensive diversity of genome architectures of tick-associated viruses, highlighting ticks as a reservoir of RNA viruses. We examined the phylogenies of different virus families to investigate virome evolution and found that the most diverse tick-associated viruses are positive-strand RNA virus families that demonstrate more ancient divergence than other arboviruses. Tick-specific viruses are often associated with only a few tick species, whereas virus clades that can infect vertebrates are found in a wider range of tick species. We hypothesize that tick viruses can exhibit both 'specialist' and 'generalist' evolutionary trends. We hope that our virome dataset will enable much-needed research on vertebrate-pathogenic tick-associated viruses.

The risk surveillance of schistosomiasis in Yunnan, 2021 / 中国热带医学

@#Abstract: Objective　To evaluate the potential transmission risk of schistosomiasis in Yunnan Province, and to provide strategic basis for the prevention and control. Methods　Based on the prevalence of schistosomiasis, the social and environmental factors that may lead to the epidemic, 1-3 villages from 3 provincial-level and 15 county-level counties (cities and districts) were selected as the evaluated villages in 2021. The risk of schistosomiasis spread was analyzed comprehensively by consulting, reviewing and collecting routine surveillance data of schistosomiasis in the villages, combined with snail and wild feces survey. The risk level was evaluated for the positive snails, positive wild feces, resident infection, average density of live snails and snail frame occurrence rate. Results　Totally 7 snail counties schistosomiasis transmission was blocked of 18 epidemic counties and the rest were eliminated counties. A total of 152 447 snail frames were investigated and 3 043 frames with snails, 15 895 snails were captured and included 15 727 live snails in the 32 evaluated villages. The total area of snail was 58.87 hm2 and the area of reoccurrence was 34.19 hm2 with snail frame occurrence rate of 2.00% and average density of live snails 0.103 2/0.11 m2, and no positive snails were found by loop-mediated isothermal amplification (LAMP) assay. A total of 1 374 wild feces were collected in 27 evaluated villages of 14 epidemic counties, mainly from cattle, dogs, sheep, equine animals, pigs and so on, all of which were negative. According to the risk assessment of epidemic spread, Yongle Village and Yongsheng Village in Eryuan County, Zhiming Village in Chuxiong City were Ⅱ risk, and the rest were Ⅲ risk. Conclusions　Although the risk of transmission is low in Yunnan Province, the risk of transmission and spread still exists. It is necessary to strengthen the risk monitoring, control of snail and effective management of livestock to prevent the rebound of the epidemic.

Complete mitogenomes and phylogenetic relationships of Haemaphysalis nepalensis and Haemaphysalis yeni.

The mitochondrial genome may include crucial data for understanding phylogenetic and molecular evolution. We sequenced the complete mitogenome of Haemaphysalis nepalensis and Haemaphysalis yeni for the first time. H. nepalensis and H. yeni's complete mitogenomes were 14,720 and 14,895 bp in size, respectively, and both contained two ribosomal RNA (rRNA) genes, 22 transfer RNA (tRNA) genes, and 13 protein-coding genes (PCG). Haemaphysalis nepalensis have one control region (D-loop). The adenine + thymine concentration of the genomes of H. nepalensis and H. yeni was 77.75 and 78.41%, respectively. The codon use pattern and amino acid content of proteins were both observed to be affected by the AT bias. Genes in the mitogenome were organized and located in a comparable manner to previously known genes from Haemaphysalis ticks. Mitochondrial PCGs were used to perform phylogenetic relationships based on the Minimum Evolution (ME) approach using MEGA 7.0 software, the results reveal that H. nepalensis has tight links with H. tibetensis, H. yeni and H. kolonini share a sister group relationship, and that H. nepalensis and H. yeni belong to Haemaphysalis. The results of this study include the following: (i) discovered and supplied new tick records (H. nepalensis) for China, (ii) provided the first complete mitochondrial genome for H. nepalensis and H. yeni and revealed their phylogenetic relationships, and (iii) the features of the mitochondrial genome of H. nepalensis and H. yeni provided more genetic reference for Phylogeography, systematics, and population genetics of the Haemaphysalis species.

Coinfection of Two Rickettsia Species in a Single Tick Species Provides New Insight into Rickettsia-Rickettsia and Rickettsia-Vector Interactions.

Rickettsiae are obligate intracellular bacteria that can cause life-threatening illnesses. There is an ongoing debate as to whether established infections by one Rickettsia species preclude the maintenance of the second species in ticks. Here, we identified two Rickettsia species in inoculum from Haemaphysalis montgomeryi ticks and subsequently obtained pure isolates of each species by plaque selection. The two isolates were classified as a transitional group and spotted fever group rickettsiae and named Rickettsia hoogstraalii str CS and Rickettsia rhipicephalii str EH, respectively. The coinfection of these two Rickettsia species was detected in 25.6% of individual field-collected H. montgomeryi. In cell culture infection models, R. hoogstraalii str CS overwhelmed R. rhipicephalii str EH with more obvious cytopathic effects, faster plaque formation, and increased cellular growth when cocultured, and R. hoogstraalii str CS seemed to polymerize actin tails differently from R. rhipicephalii str EH in vitro. This work provides a model to investigate the mechanisms of both Rickettsia-Rickettsia and Rickettsia-vector interactions. IMPORTANCE The rickettsiae are a group of obligate intracellular Gram-negative bacteria that include human pathogens causing an array of clinical symptoms and even death. There is an important question in the field, that is whether one infection can block the superinfection of other rickettsiae. This work demonstrated the coinfection of two Rickettsia species in individual ticks and further highlighted that testing the rickettsial competitive exclusion hypothesis will undoubtedly be a promising area as methods for bioengineering and pathogen biocontrol become amenable for rickettsiae.

Characterization of the complete mitochondrial genome of Ixodes granulatus (Ixodidae) and its phylogenetic implications.

Ticks are deemed to be second only to mosquitoes as the most common vector of human infectious diseases worldwide that give rise to human and animal diseases and economic losses to livestock production. Our understanding of the phylogenetic analysis between tick lineages has been restricted by the phylogenetic markers of individual genes. Genomic data research could help advance our understanding of phylogenetic analysis and molecular evolution. Mitochondrial genomic DNA facilitated the phylogenetic analysis of eukaryotes containing ticks. In this study, we sequenced and assembled the circular complete mitogenome information of Ixodes granulatus. The 14,540-bp mitogenome consists of 37 genes, including 13 protein-coding genes (PCGs), two genes for ribosomal RNA (rRNAs), and 22 genes for transfer RNA (tRNAs), and the origin of the L-strand replication region. The directions of the coding strand and component genes in the non-Australasian Ixodes mitochondrial genome were similar to those found in most other Australasian Ixodes, except for the loss of a lengthy control region. The phylogenetic tree based on maximum likelihood (ML) and Bayesian inference (BI) computational algorithms showed that I. granulatus exhibits a close relationship with I. hexagonus and I. ricinus. To our knowledge, this is the first study exploring the complete mitogenome for the species I. granulatus. Our results provide new insights for further research on the evolution, population genetics, systematics, and molecular ecology of ticks.

Characterization of the complete mitochondrial genome of Haemaphysalis (Alloceraea) kolonini (Ixodidae) and its phylogenetic implications.

Ticks transmit diverse pathogens that cause human and animal diseases, leading to an increasing number of new challenges around the world. Genomic data research could help advance our learning of phylogenetic analysis and molecular evolution. Mitochondrial genome DNA has been helpful in illustrating the phylogenetic analysis of eukaryotes containing ticks. In this research, we sequenced and assembled the circular complete mitogenome information of Haemaphysalis kolonini. The 14,948-bp mitogenome consists of 37 genes which included 13 genes for protein-coding, two genes for ribosomal RNA, 22 genes for transfer RNA, and two control regions (D-loops). Overall, the composition and arrangement of genes were compared with Haemaphysalis ticks previously recorded in Genbank. The phylogenetic tree based on Maximum likelihood (ML) and Bayesian inference (BI) computational algorithms showed that H. kolonini has a close relationship with Haemaphysalis inermis. The complete mitogenome data provide a preferable perception to the phylogenetic relationship than the single-gene data analysis. To our knowledge, this is the first research exploring the complete mitogenome for the species H. kolonini. Our results provide new insights for further research on the evolution, population genetics, systematics, and molecular ecology of ticks.

Molecular evidence of Candidatus Rickettsia longicornii and a novel Rickettsia strain from ticks in Southern China.

Ticks and tick-borne rickettsial diseases have been gaining greater attention in China over the past decade. However, most published studies to date have occurred in Northern China, with limited investigations occurring in China's southern provinces. As part of larger surveillance efforts, a cross-sectional survey was conducted in six sites at Guangdong, Guangxi and Yunnan investigating rickettsial infection in ticks. A total of 581 ticks were collected from hosts and screened via PCR, targeting rrs, gltA, ompB, sca4, and ompA gene fragments. Two of 12 Haemaphysalis formosensis ticks were infected with novel Rickettsia strain GD01, which was closest phylogenetically (97.3-98.9 % identity) to Rickettsia tamurae strain AT-1, but not within the same clade. Another detected strain (GD02) shared similar identity, 99-100 % across four gene targets, to recently detected Candidatus Rickettsia longicornii isolate ROK-HL727, with an overall prevalence of 12.5 % (71/569). The presence of such pathogens calls for increased public health attention and active surveillance in patients reporting recent tick bites.

Detection of Novel Spotted Fever Group Rickettsiae (Rickettsiales: Rickettsiaceae) in Ticks (Acari: Ixodidae) in Southwestern China.

Spotted fever group rickettsiae, mainly maintained and transmitted by ticks, are important etiological agents of (re)emerging zoonotic diseases worldwide. It is of great significance to investigate spotted fever group rickettsiae in ticks in different areas for the prevention and control of rickettsioses. In this study, a total of 305 ticks were collected from wild and domestic animals in Chongqing, Guizhou, Yunnan, and Guangxi provinces of southwestern China during 2017-2019 and examined for the presence of spotted fever group rickettsiae by PCR with primers targeting the partial gltA, ompA, rrs, and htrA genes. Results showed that two spotted fever group rickettsiae species, including the pathogenic Candidatus Rickettsia jingxinensis (Rickettsiales: Rickettsiaceae) and a potential novel species Rickettsia sp. sw (Rickettsiales: Rickettsiaceae), were identified. The Ca. R. jingxinensis sequences were recovered from Rhipicephalus microplus (Ixodida: Ixodidae) and Haemaphysalis longicornis (Ixodida: Ixodidae) ticks and phylogenetically clustered with previous Ca. R. jingxinensis, Ca. R. longicornii (Rickettsiales: Rickettsiaceae), and Rickettsia sp. XY118 (Rickettsiales: Rickettsiaceae) strains. Rickettsia sp. sw was detected in Amblyomma geoemydae (Ixodida: Ixodidae) and Rh. microplus. Interestingly, as far as we know, this was the first report of Rickettsia (Rickettsiales: Rickettsiaceae) in A. geoemydae. Phylogenetic analyses indicated that this potential novel species was closely related to R. aeschlimannii (Rickettsiales: Rickettsiaceae) with gltA and ompA genes and grouped in a cluster composed of R. montanensis (Rickettsiales: Rickettsiaceae), R. raoultii (Rickettsiales: Rickettsiaceae), R. aeschlimannii, R. massiliae (Rickettsiales: Rickettsiaceae), and R. rhipicephali (Rickettsiales: Rickettsiaceae) with htrA, while formed a separate clade with rrs. The pathogenicity of Rickettsia sp. sw should be further confirmed. These results expand the knowledge of the geographical distribution and vector distribution of spotted fever group rickettsiae in China and are useful for assessing the potential public health risk.

Large-Scale Comparative Analyses of Tick Genomes Elucidate Their Genetic Diversity and Vector Capacities.

Among arthropod vectors, ticks transmit the most diverse human and animal pathogens, leading to an increasing number of new challenges worldwide. Here we sequenced and assembled high-quality genomes of six ixodid tick species and further resequenced 678 tick specimens to understand three key aspects of ticks: genetic diversity, population structure, and pathogen distribution. We explored the genetic basis common to ticks, including heme and hemoglobin digestion, iron metabolism, and reactive oxygen species, and unveiled for the first time that genetic structure and pathogen composition in different tick species are mainly shaped by ecological and geographic factors. We further identified species-specific determinants associated with different host ranges, life cycles, and distributions. The findings of this study are an invaluable resource for research and control of ticks and tick-borne diseases.

[Community structure and distribution pattern of small mammals in agricultural area of Yunnan Province, China.] / äº‘å—çœå†œè€•åŒºå°åž‹å ½ç±»ç¾¤è½ç»“æž„åŠåˆ†å¸ƒæ ¼å±€.

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.

Role of ecological approaches to eliminating schistosomiasis in Eryuan County evaluated by system modelling.

BACKGROUND: Schistosomiasis was severely prevalent in Yunnan Province, and it is difficult to achieve its elimination by convention approaches due to complexity of the nature. We explored the comprehensive model to eliminate schistosomiasis in Eryuan County, Yunnan Province, the People's Republic of China, through integration with the ecological protection programme in Erhai Lake, in order to promote an efficient elimination strategy. We expected that this model is able to be tailored to other local settings, which help achieve the goal of precisely eliminating the disease in Yunnan Province. METHODS: Eryuan County of Yunnan Province was chosen as the study area, where the data on environmental protection activities in Erhai Lake and on the schistosomiasis control programme were collected through different departments of Erhai County government since 2015. System modelling was performed using system dynamics software to establish a simulation model in order to evaluate the effectiveness of intervention activities. RESULTS: Ecological approaches to control schistosomiasis in Eryuan County consist of three major components: (i) implementing precise interventions to stop schistosomiasis transmission by means of controlling the source of infection, blocking the biological transmission chains and cutting off the route of disease transmission; (ii) employing ecological approaches to improve the co-effectiveness of environmental protection and schistosomiasis prevention in the study area; and (iii) strengthening the professional skills of personnel involving in the schistosomiasis control programme. Simulation results showed that this strategy could speed up the progress of schistosomiasis control programme moving from the control stage to the elimination stage. CONCLUSIONS: Ecological approaches implemented in schistosomiasis endemic areas of the Eryuan region are able to improve the co-effectiveness of environmental protection and schistosomiasis control, providing a new avenue for eliminating schistosomiasis thanks to the application of precise interventions.

Description of Haemaphysalis (Alloceraea) Kolonini sp. nov., a new species in subgenus Alloceraea Schulze (Ixodidae: Haemaphysalis) in China.

Southeastern Asia has been postulated as probably the original sites of genus Haemaphysalis, where numerous structurally advanced haemaphysalids now occur. Because of its phylogenetic and biological interest, we report the discovery of a structurally primitive new species Haemaphysalis (A.) kolonini belonging to subgenus Alloceraea from Baoshan and Weixi cities, Yunnan province, southwestern China. Both the morphological and phylogenic characteristics of the species support congruently to erect Hae. (A.) kolonini as a new species. The male and female adults of Haemaphysalis (A.) kolonini are respectively described and illustrated. Taxonomic discussion and keys to Alloceraea species in China are also provided to be able to distinguish species that are close morphologically.

Investigation on Ehrlichia Infection in Small Mammals and Ticks from Tengchong, Yunnan Province, Southern China.

BACKGROUND: Rare investigation on tick-borne pathogens was carried out in Yunnan, China. In this study, we did a survey on Ehrlichia infection in small mammals and ticks. A total of 40 small mammals and 49 ticks were collected from Tengchong, Yunnan province. PCR targeting 16S ribosomal RNA (rRNA), citrate synthase, GroEL heat-shock protein operon, and major outer membrane protein genes was performed and positive amplicons were sequenced. RESULTS: The 40 small mammals were identified as 10 species, 2 (5.0%) of which were infected with Ehrlichia, 4 (10.0%) were infected with Anaplasma phagocytophilum and another 2 (5.0%) were infected with Candidatus Neoehrlichia mikurensis. Six (12.2%) ticks were positive for Ehrlichia and another two (4.1%) were infected with A. phagocytophilum. Neither small mammals nor ticks had coinfection. The detected Ehrlichia was named as Ehrlichia sp. YN04, which was in the same clade of Ehrlichia sp. 360 by phylogenetic analysis. The sequences of the pathogen recovered from small mammals and ticks were identical with each other. CONCLUSION: The study reports one Ehrlichia species first detected from small mammals and ticks in mainland China. As Yunnan is a famous "Global Biodiversity Hotspot" in the world, we may expect much more tick-borne infectious pathogens existing and declare more public health attention in this region.

Wide Distribution and Genetic Diversity of Babesia microti in Small Mammals from Yunnan Province, Southwestern China.

BACKGROUND: Babesia, usually found in wild and domestic mammals worldwide, have recently been responsible for emerging malaria-like zoonosis in infected patients. Human B. microti infection has been identified in China, primarily in the Southwest along the Myanmar border but little direct surveillance of B. microti infection in rodents has been carried out here (Yunnan province). In this region, a diverse topographic range combined with tropical moisture sustains a high biodiversity of small mammals, which might play important role on Babesia transmission. METHODS: Small mammals were captured in 141 sample locations from 18 counties located Yunnan Province, and screened for B. microti-like parasites infection by a nested PCR to target 18S rRNA gene of Babesia, plus directly sequencing for positive samples. Univariate and multivariate forward stepwise logistic regression analysis was used to access the association between infections and some related risk factors. RESULTS: Infection with Babesia microti was confirmed in 2.4% (53/ 2204) of small mammals. Significant differences in prevalence rates of B. microti were observed based on variations in forest, agricultural, and residential landscapes. Furthermore, adult small mammals had higher prevalence rates than younger, pubertal mammals. The near full-length 18S rRNA gene revealed that there were two types of B. microti, Kobe and Otsu, which demonstrate the genetic diversity and regional distribution. CONCLUSIONS: There exists a wide distribution and genetic diversity of endemic B. microti in Southwestern China, warranting further investigations and monitoring of clinical disease in individuals presenting with Babesia like symptoms in these areas.

[Predictors for abundance of Rattus tanezumi in households of commensal rodent plague foci].

OBJECTIVE: To explore the predictors on the abundance of Rattus (R.) tanezumi in households of commensal rodent plague foci. METHODS: Thirty natural villages that experienced previous plague cases in Lianghe county, Yunnan province, were selected followed by random selection of 20 households in each village through computer technique. Live traps were set in households to capture small mammals which were then identified to species in the field according to their morphological features. Data on potential factors for abundance of R. tanezumi were collected through questionnaires and field observation and were coded and computerized using EpiData software and further analyzed by hurdle regression model under R software. RESULTS: A total of 166 rodents (133 R. tanezumi and 33 Suncus murinus) were captured. RESULTS: from final multilevel hurdle regression model showed that the likelihood of R. tanezumi captures increased by 1.67- to 2.76-fold in households belonged to Dai ethnic families that stored foodstuff in metal pail, often raising dogs, and having adjacent houses. The number of R. tanezumi captures increased by 2.18-fold in the villages where over 80% of the households would raise chickens. In the villages with communal latrine, the likelihood and the number of R. tanezumi capture increased 1.93-fold and 2.38-fold, respectively. While the likelihood of R. tanezumi captures would reduce by 45% - 61% in those households where there were cats and cattle being raised and maize grown in the village. The number of R. tanezumi captures would reduce by 63% in the households where there were outside toilet. CONCLUSION: The abundance of R. tanezumi seemed to be closely related to the ecological environment factors. Programs on plague control and prevention should relate to ecological factors that influencing the abundance of R. tanezumi.

[Preparation and identification of monoclonal antibodies against Pla protein of Yersinia pestis].

AIM: To prepare the monoclonal antibody of Pla with recombinant Pla (rPla) by hybridoma cell technology, which will lay the foundation for related research work. METHODS: Purified rPla was collected by washing repeatedly with urea, and BALB/c mice were immunized by them. Hybridoma cells were achieved by Sp2/0 cell fusion with mouse spleen cells from successfully immunized mice. Monoclonal antibody was screened by indirect ELISA and Western blots with rPla, natural crude Pla and GST respectively. RESULTS: Three strains of hybridoma cells (named 15B8, 14H4 and 19A4 respectively) which secreted stably the monoclonal antibody of Pla were obtained. Their subclasses were IgG2a and IgG1 in heavy chains and κ chains in light chains. The ELISA titers of ascites were 10(6); respectively.Three of monoclonal antibody can react with natural crude Pla tested by western blots. CONCLUSION: Monoclonal antibody of natural Pla of Yersinia pestis were successfully got, which has laid the foundation for further study of the Pla protein and development diagnosis reagent.

Predictors for abundance of host flea and floor flea in households of villages with endemic commensal rodent plague, Yunnan Province, China.

BACKGROUND: From 1990 to 2006, fifty-five natural villages experienced at least one plague epidemic in Lianghe County, Yunnan Province, China. This study is aimed to document flea abundance and identify predictors in households of villages with endemic commensal rodent plague in Lianghe County. METHODS: Trappings were used to collect fleas and interviews were conducted to gather demography, environmental factors, and other relevant information. Multivariate hurdle negative binomial model was applied to identify predictors for flea abundance. RESULTS: A total of 344 fleas were collected on 101 small mammals (94 Rattus flavipectus and 7 Suncus murinus). R. flavipectus had higher flea prevalence and abundance than S. murinus, but the flea intensities did not differ significantly. A total of 315 floor fleas were captured in 104 households. Xenopsylla cheopis and Ctenocephalides felis felis were the predominant flea species on the host and the floor flea, respectively. The presence of small mammal faeces and R. flavipectus increased host flea prevalence odds 2.9- and 10-fold, respectively. Keeping a dog in the house increased floor flea prevalence odds 2-fold. Keeping cattle increased floor flea intensity by 153%. Villages with over 80% of houses raising chickens had increased prevalence odds and intensity of floor flea about 2.9- and 11.6-fold, respectively. The prevalence and intensity of floor flea in brick and wood houses were decreased by 60% and 90%, respectively. Flea prevalences of host and floor flea in the households that were adjacent to other houses were increased 7.4- and 2.2-fold, respectively. Houses with a paddy nearby decreased host flea intensity by 53%, while houses with an outside toilet increased host flea intensity by 125%. CONCLUSION: Rodent control alone may not be sufficient to control plague risk in these areas. In order to have successful results, plague control programs should pay attention to ecological and hygiene factors that influence flea populations.

Predictors for presence and abundance of small mammals in households of villages endemic for commensal rodent plague in Yunnan Province, China.

BACKGROUND: Ninety-one rodent plague epidemics have occurred in Lianghe county, Yunnan Province, China, between 1990 and 2006. This study aimed to identify predictors for the presence and abundance of small mammals in households of villages endemic for rodent plague in Lianghe county. RESULTS: Rattus flavipectus and Suncus murinus were the two species captured in 110 households. Keeping cats decreased the number of captures of R. flavipectus by one to two thirds and the chance of reported small mammal sightings in houses by 60 to 80%. Food availability was associated with fewer captures. Keeping food in sacks decreased the small mammal captures, especially of S. murinus 4- to 8-fold. Vegetables grown around house and maize grown in the village reduced the captures of S. murinus and R. flavipectus by 73 and 45%, respectively. An outside toilet and garbage piles near the house each reduced R. flavipectus captures by 39 and 37%, respectively, while raising dogs and the presence of communal latrines in the village increased R. flavipectus captures by 76 and 110% but were without detectable effect on small mammal sightings. Location adjacent to other houses increased captures 2-fold but reduced the chance of sightings to about half. In addition, raising ducks increased the chance of sighting small mammals 2.7-fold. Even after adjusting for these variables, households of the Dai had higher captures than those of the Han and other ethnic groups. CONCLUSION: Both species captures were reduced by availability of species-specific foods in the environment, whereas other predictors for capture of the two species differed. Other than the beneficial effect of cats, there were also discrepancies between the effects on small mammal captures and those on sightings. These differences should be considered during the implementation and interpretation of small mammal surveys.