Niviventer Fulvescens Research Articles

Physical seed damage, not rodent's saliva, accelerates seed germination of trees in a subtropical forest.

Many tree species adopt fast seed germination to escape the predation risk by rodents. Physical seed damage and the saliva of rodents on partially consumed seeds may act as cues for seeds to accelerate germination process. However, the impacts of these factors on seed germination rate and speed remain unclear. In this study, we investigated such impacts on the germination rate and speed (reversal of germination time) of four tree species (Quercus variabilis, Q. serrata, Q. acutissima, Q. glauca) after partial consumption by four rodent species (Leopoldamys edwards, Niviventer fulvescens, N. confucianus, Apodemus draco), through a series of experiments. We also examined how seed traits may affect the seed damage degree by rodents by analyzing the relationship between the germination rate and time of rodent-damaged seed and the traits. We found that, artificially- and rodent-damaged seeds exhibited a significantly higher seed germination rate and speed, compared to intact seeds. Also, the rodent saliva on seeds showed no significant effect on seed germination rate and speed. Furthermore, we observed significant positive correlations between several seed traits (including the seed mass, coat thickness, and protein content) and the seed germination rate and speed. These correlations are likely due to their beneficial traits countering seed damage by rodents. Overall, our results highlight the significant role of physical seed damage by rodents (rather than their saliva) in facilitating seed germination of tree species, and potential mutualism between rodents and trees. Additionally, our results may have some implications in forest restoration, such that intentionally sowing or dispersing slightly damaged seeds by humans or drones may increase the likelihood of successful seed regeneration.

Molecular Prevalence, Genetic Diversity, and Tissue Tropism of Bartonella Species in Small Mammals from Yunnan Province, China.

Bartonella is an intracellular parasitic zoonotic pathogen that can infect animals and cause a variety of human diseases. This study investigates Bartonella prevalence in small mammals in Yunnan Province, China, focusing on tissue tropism. A total of 333 small mammals were sampled from thirteen species, three orders, four families, and four genera in Heqing and Gongshan Counties. Conventional PCR and real-time quantitative PCR (qPCR) were utilized for detection and quantification, followed by bioinformatic analysis of obtained DNA sequences. Results show a 31.5% detection rate, varying across species. Notably, Apodemus chevrieri, Eothenomys eleusis, Niviventer fulvescens, Rattus tanezumi, Episoriculus leucops, Anourosorex squamipes, and Ochotona Thibetana exhibited infection rates of 44.4%, 27.7%, 100.0%, 6.3%, 60.0%, 23.5%, and 22.2%, respectively. Genetic analysis identified thirty, ten, and five strains based on ssrA, rpoB, and gltA genes, with nucleotide identities ranging from 92.1% to 100.0%. Bartonella strains were assigned to B. grahamii, B. rochalimae, B. sendai, B. koshimizu, B. phoceensis, B. taylorii, and a new species identified in Episoriculus leucops (GS136). Analysis of the different tissues naturally infected by Bartonella species revealed varied copy numbers across different tissues, with the highest load in spleen tissue. These findings underscore Bartonella's diverse species and host range in Yunnan Province, highlighting the presence of extensive tissue tropism in Bartonella species naturally infecting small mammalian tissues.

Disease vector occurrence and ecological characteristics of chiggers on the chestnut white-bellied rat Niviventer fulvescens in Southwest China between 2001 and 2019.

Chigger mites are the vector of scrub typhus. This study estimates the infestation status and ecological characteristics of chiggers on the chestnut white-bellied rat Niviventer fulvescens in Southwest China between 2001 and 2019. Chiggers were identified under the microscope, and infestation indices were calculated. The Preston's log-normal model was used to fit the curve of species abundance distribution. A total of 6,557 chiggers were collected in 136 of 342 N. fulvescens rats, showing high overall infestation indices (prevalence=39.8%, mean abundance=19.2, mean intensity=48.2) and high species diversity (S=100, H'=3.0). Leptotrombidium cangjiangense, Neotrombicula japonica, and Ascoschoengastia sifanga were the three dominant chigger species (constituent ratio=42.9%; 2,736/6,384) and exhibited an aggregated distribution among different rat individuals. We identified 100 chigger species, with 3 of them (Leptotrombidium scutellare, Leptotrombidium wenense, and Leptotrombidium deliense) as the main vectors of scrub typhus in China and nine species as potential vectors of this disease. Disease vector occurrence on N. fulvescens may increase the risk of spreading scrub typhus from rats to humans. Chigger infestation on N. fulvescens varied significantly in different environments. The species abundance distribution showed a log-normal distribution pattern. The estimated number of chigger species on N. fulvescens was 126 species.

Species diversity, abundance, and movement of small mammals in the dry evergreen forest at Khao Yai National Park, Thailand

Abstract. Chanachai Y, Nathalang A, Duengkae P, Sukmasuang R. 2022. Species diversity, abundance, and movement of small mammals in the dry evergreen forest at Khao Yai National Park, Thailand. Biodiversitas 23: 5892-5901. Small mammals play an integral role in the forest ecosystem. This research was conducted on The Mo Singto Forest Dynamics Plot, Khao Yai National Park. Trapping of small mammals was carried out in June-September 2019 and from January-April 2020 based on a total of 64 Tomahawk for small mammal live traps were systematically placed in an 8×8 grid of 20 m intervals, ripe bananas and palm oil as bait was used. Trap cages were opened for 3 consecutive months per season in each study period covering a total study period of 1 year. The result showed that a total of 4015 individuals from 9 species, 9 genera, 4 families and 3 orders were captured with a sampling effort of 32,555 trap nights. The most common species were Red Spiny Rat (Maxomys surifer), followed by Northern Tree Shrew (Tupaia belangeri), Long-tailed Giant Rat (Leopoldamys sabanus), Indochinese Ground Squirrel (Menetes berdmorei), Asian House Rat (Rattus tanezumi), Indomalayan Niviventer (Niviventer fulvescens), Savile's Bandicoot Rat (Bandicota savilei), (Tamiops mcclellandii), and Short-tailed Gymnure (Hylomys suillus) respectively. Considering the number of small mammals caught, Maxomys surifer was the most abundant, accounting for 61.69% of all mammals caught. The sex ratio was found to somewhat favor females in both seasons. This study indicated that the small mammal diversity was high in the primary dry evergreen forest. These results have important implications not only for conservation but are also useful for further investigation if there is any disturbance or change in the area or any potential disasters that may occur in the future.

Additional Records of Small Mammals Collected from Nepal

Small mammals were surveyed in areas of the Annapurna Conservation Area, Shey Phoksundo National Park, and the Manaslu Conservation Area between 2013 and 2015. We collected 117 specimens representing 10 species of small mammals from two orders, Soricomorpha and Rodentia. We report on localities sampled from Central Nepal expanding known distributions and reporting new sampling localities for Apodemus gurkha Thomas, 1924; Apodemus pallipes (Barrett-Hamilton, 1900); Mus musculus Linnaeus, 1758; Niviventer fulvescens (Gray, 1847); Rattus rattus (Linnaeus, 1758); Rattus pyctoris (Hodgson, 1845); Rattus nitidus (Hodgson, 1845); and Soriculus nigrescens (Gray, 1842). Specimens collected from the Manaslu Conservation Area, which had not been previously surveyed, documented the occurrence of four species between previously known collection localities in the Kali Gandaki Valley and the Langtang and Khumbu valleys. Distribution records of Episoriculus soluensis Gruber, 1969 in Nepal are clarified for this recently recognized species.

Incidence of leptospirosis in Fujian province, 2015-2020

Objective: To analyze the incidence of leptospirosis in Fujian province from 2015 to 2020 and provide the scientific evidences for the risk assessment, prevention and control of leptospirosis. Methods: The incidence data of leptospirosis in Fujian during 2015-2020 were collected from China Information System for Disease Control and Prevention for a descriptive analysis, and software ArcGIS 10.3.1 was used for spatial autocorrelation analysis, and rats were captured in 17 surveillance areas during the same period, and the rat organs were collected for pathogen culture, the level of Leptospira antibody was detected in serum samples of rats, healthy population and the serum samples of patients sent by the hospitals. The infection status of Leptospira in human and rats were analyzed. Results: The incidence of leptospirosis in Fujian showed a downward trend from 2015 to 2020. A total of 176 cases of leptospirosis were reported. There were obvious seasonality and bimodal distribution. The majority of cases were farmers, accounting for 49.43% (87/176). Most cases were aged 30-69 years (85.80%, 151/176). The male to female ratio of the cases was 3.51∶1 (137∶39). Spatial autocorrelation analysis showed that leptospirosis had high or low clustering areas. From 2015 to 2020, the average capture rate of rats in 17 surveillance areas was 6.96% (1 519/21 838), Rattus losea, Rattus flavipectus and Niviventer fulvescens were the main species. The average positive rate of Leptospira antibody in rats was 28.64% (252/880). Java and Autumnalis were the predominant serogroups, accounting for 56.75% (143/252) and 17.46% (44/252), respectively. The average positive rate of Leptospira antibody in healthy population was 16.13% (254/1 575), and Autumnalis and Australis were the predominant serogroups, accounting for 71.65% (182/254). The confirmation rate of leptospirosis in patient serum samples sent by the hospitals was 2.23% (188/8 431), Autumnalis (56.38%, 106/188) and Hebdomadis (19.68%, 37/188) were the major serogroups. Conclusions: The incidence of leptospirosis in Fujian showed a downward trend from 2015 to 2020, there were obvious area clustering and seasonality. The high clustering areas were mainly distributed in northern, western and central Fujian. Java and Autumnalis were the predominant serogroups in rats. The infection rate in healthy population decreased year by year. Autumnalis and Hebdomadis were the main serogroups in population in Fujian.

Habitats Show More Impacts Than Host Species in Shaping Gut Microbiota of Sympatric Rodent Species in a Fragmented Forest.

Gut microbiota play a significant role for animals to adapt to the changing environment. Host species and habitats are key drivers in shaping the diversity and composition of the microbiota, but the determinants of composition of the sympatric host gut microbiome remain poorly understood within an ecosystem. In this study, we examined the effects of habitats of different succession stages and host species on the diversity and composition of fecal gut microbiota in four sympatric rodent species (Apodemus draco, Leopoldamys edwardsi, Niviventer confucianus, and Niviventer fulvescens) in a subtropical forest. We found, as compared to the differences between species, habitat types showed a much larger effect on the gut microbiota of rodents. Alpha diversity of the microbial community of A. draco, N. fulvescens, and N. confucianus was highest in farmland, followed by primary forest and shrubland, and lowest in secondary forest. Beta diversity of the three rodent species showed significant different among habitats. The alpha diversity of gut microbiota of L. edwardsi was significantly higher than those of A. draco and N. confucianus, and its beta diversity showed significant difference from A. draco. Our results suggested that gut microbiota were important for animals in responding to diet changes in different habitats under human disturbances.

The Non-Volant Terrestrial Small Mammals at Ulu Muda Forest Reserve, Kedah, Malaysia

An eight days survey of non-volant small mammals was conducted at the Ulu Muda Forest Reserve in the state of Kedah, Malaysia. To sample the small mammals, we placed 100 cage traps and 50 bucket pitfall traps randomly along the existing man-made trails in four sampling sites within the study area. Total trapping effort for the cage traps was 796 trap nights, while the total trapping effort for the bucket pitfall traps was 400 trap nights. Overall, 24 non-volant small mammal individuals represented by seven species from the Family Muridae were captured. The Red spiny rat, Maxomys surifer, was the most dominant species accounting for 42% of the total individuals captured. We also caught the Chestnut white-bellied rat (Niviventer fulvescens) which is a new record for the study area. Although sampling was conducted only briefly, our study has demonstrated that Ulu Muda Forest Reserve still holds a high diversity of forest rat species, some of which are of international or regional conservation concern. Increasing the sampling effort, i.e., by surveying more areas over a longer period, would likely increase the possibility of capturing more small mammal species in this area.

Keragaman, Dominasi Tikus Silvatik, Kepadatan Pinjal dan Kewaspadaan Pes di Daerah Fokus Pes di Kecamatan Cepogo Kabupaten Boyolali

One of rodent borne diseases that exist in Indonesia is pes with flea as vector and rat as reservoir. The objective of this research were to find out the diversity, dominance of rats, the density of rat and fleas as monitoring efforts for vigilance of plague transmission. The study was conducted in September-October 2016 in Wonodoyo and Kembang Kuning village, Cepogo Sub District of Boyolali District. The research is descriptive with cross sectional approach. Samples collection were conducted by rats survey used single live trap in the silvatic area. The results showed that rats trap success in Wonodoyo village was 3.8% (38 rats) and 1,1% (11 rats) in Kembang Kuning village. Four kind of silvatic rats were Rattus exulans, R. tiomanicus, Niviventer fulvescens and Maxomys surifer. Most of the rats caught (73.68%) in Wonodoyo Village were infested with fleas, while in Kembang Kuning Village it was 27.27%. All of fleas identified as Stivalius cognatus. The specific and general flea index value of S. cognatus in Wonodoyo Village is 2.66; Kembang Kuning Village is 0.45. Early vigilance is very important to do to prevent the transmission of bubonic plague originating from silvatic rats in Cepogo District, particularly in Wonodoyo Village.

Rat‐ and bat‐pollination of Mucuna championii (Fabaceae) in Hong Kong

AbstractMucuna (Fabaceae) species possess gullet‐type flowers that open explosively and which are thought to be specifically adapted for bat‐ or bird‐pollination. However, recent studies have shown that non‐flying mammals are also important pollinators of this genus in Asia. Here we report on the pollination system of Mucuna championii (endemic in southeast China) in Hong Kong. As is typical for the genus, explosive opening is essential for fruit set, but flowers are unable to open in the absence of manipulation by an effective pollinator. Camera trap surveys of three individuals revealed both chestnut spiny rats (Niviventer fulvescens) and short‐nosed fruit bats (Cynopterus sphinx) to be capable of triggering explosive opening. The number of flowers opened by each species did not differ significantly, and both removed most pollen grains from the flowers they visited, but either species visited different individuals. Sucrose‐rich nectar was secreted by flowers throughout the day. Our results reveal that M. championii can be pollinated by both rats and bats, with this representing only the second report of rat‐pollination in tropical Asia. The sympatric M. birdwoodiana often occurs in close proximity to M. championii and has an overlapping flowering season, suggesting that pollinator segregation may have played a role in shaping the evolutionary ecology of these two species.

Molecular phylogeny and morphological diversity of theNiviventer fulvescensspecies complex with emphasis on species from China

AbstractThe Niviventer fulvescens species complex (NFSC), a group of abundant and taxonomically ambiguous rodent taxa, is distributed from Southeast Asia to south-eastern China. We combined molecular and morphological datasets to clarify the species composition and variation of the NFSC. Our phylogenetic analyses, using molecular data, recovered eight genetic lineages in the NFSC, including a novel, distinct lineage from Jilong, Tibet, China, which is described as a new species, N. fengi sp. nov. The species status of N. fengi is supported by a species delimitation analysis, and it is morphologically distinguished from other members of the NFSC by its greyish dorsal fur, soft hairs covering the whole body and a hairy tail. NFSC species bearing well-developed spines are found at lower elevations. A comprehensive taxonomic revision of the NFSC within China is provided, represented by five species: N. cremoriventer, N. fulvescens, N. huang, N. mekongis comb. nov. and N. fengi. A further study of this species complex, including samples from Southeast Asia, is needed.

Cryptosporidium spp. in wild rats (Rattus spp.) from the Hainan Province, China: Molecular detection, species/genotype identification and implications for public health.

Wild rats (Rattus spp.) carry many zoonotic pathogens including Cryptosporidium. Due to the close proximity of rats to humans in urban environments, the potential for disease transmission is high. Cryptosporidium is a protozoan parasite which when ingested causes serious human illness. Despite its importance, genetic characterization of Cryptosporidium in wild rats in the Hainan province of China has not been performed. In this study, we analyzed the occurrence and genetics of Cryptosporidium in wild rats from Hainan, China. From December 2017 to October 2018, 150 wild rats were captured and fresh fecal material was collected from intestinal sections. Rat species were identified by PCR-based amplification and analysis of the vertebrate cytochrome b (cytb) gene. Cryptosporidium was examined by PCR amplification of the partial small subunit of ribosomal DNA (SSU rDNA). C. viatorum were subtyped by PCR analysis of the gp60 gene. A total of four rat species were identified including Asian house rats (Rattus tanezumi) (n = 46), brown rats (Rattus norvegicus) (n = 56), Edward's long-tailed rats (Leopoldamys edwardsi) (n = 38) and muridae (Niviventer fulvescens) (n = 10), with Cryptosporidium positive rates of 73.9%, 28.6%, 55.3% and 40.0%, respectively (average infection rate: 50.0%, 75/150. Sequence analysis confirmed the presence of four Cryptosporidium species and two genotypes including C. viatorum (n = 11); C. occultus (n = 2); C. muris (n = 1); and C. erinacei (n = 1); rat genotypes III (n = 13) and IV (n = 47). Three novel subtypes of C. viatorum were identified in 6 of the 11 infected Edward's long-tailed rats: XVcA2G1a (n = 4), XVcA2G1b (n = 1) and XVdA3 (n = 1). The identification of human pathogenic C. viatorum and zoonotic C. occultus, C. muris and C. erinacei, suggested that wild rats infected with Cryptosporidium pose a threat to human health. Taken together, these findings highlight the need to control the rat population in Hainan, China. The need to improve the public awareness of the risk of disease transmission from wild rats to humans is also highlighted.

Scatter-hoarding rodents are better pilferers than larder-hoarders

Food hoarding is critical to rodents for their survival and reproduction. However, the seeds cached by rodents often suffer heavy pilferage by competitors. Therefore, compensation for cache loss is crucial, especially for scatter-hoarding rodents, as they cannot aggressively defend their stored seeds, whereas larder-hoarding rodents can. Pilfering caches of other individuals may be an effective way to compensate for cache loss for rodents. Hence, cache pilfering is likely to be as important as hoarding to food-hoarding rodents. Scatter-hoarding rodents may rely on their olfactory abilities and explore a wide area to retrieve their cached seeds, which may help to increase the probability of encountering and pilfering others' caches, whereas it is not essential for larder-hoarding rodents. We hypothesized that rodents that showed stronger scatter-hoarding behaviour would be better pilferers. To test this hypothesis, we investigated the relationship between scatter-hoarding and pilferage behaviours among four coexisting species of rodents using seminatural enclosure experiments in southwest China. Both hoarding and cache pilfering differed significantly between the four species. The predominant scatter-hoarding rodents, red spiny rats, Maxomys surifer, had a strong cache-pilfering behaviour, whereas yellow-bellied rats, Rattus flavipectus, mainly adopted larder-hoarding strategies and had a weak cache-pilfering behaviour. Chinese white-bellied rats, Niviventer confucianus, and chestnut rats, Niviventer fulvescens, had moderate scatter-hoarding and cache-pilfering behaviours. The intensity of cache pilfering was negatively correlated with the intensity of larder hoarding, but positively correlated with the intensity of scatter hoarding among the coexisting food-hoarding rodents. Our study suggests that the positive correlation between the intensities of scatter hoarding and cache pilfering is likely to facilitate reciprocal pilferage among scatter-hoarding rodents, which helps to maintain the stability of scatter-hoarding behaviour in these populations.

Identification of Muridae Species and Their Food Resources Using Dna Barcoding in Cat Tien National Park, Vietnam

Abstract. Field surveys of species in the family Muridae and their food resources were conducted in Cat Tien National Park, Vietnam in March 2011 and March and September 2012. Species were identified by DNA barcoding using polymorphic mitochondrial DNA sequences (COI, Cyt b, and D-loop) and external morphology. A total of four species, Maxomys surifer, Niviventer fulvescens, N. bukit, and Rattus sp. were identified. In order to identify which food resources were utilized by these species in the study area, total DNA was extracted from the gastric contents of the collected individuals. Sequence fragments of the chloroplast rbcL and the mitochondrial COI genes were amplified by PCR from the gastric contents and used to identify plant and animal food resources, respectively. We detected 34 plant families and seven animal orders by the homology search using the BLAST algorithm.

Sequencing and analysis of complete mitochondrial genome of Niviventer fulvescens (Muridae)

The complete mitochondrial genome was sequenced and annotated newly from an individual of Niviventer fulvescens (Muridae) from Sichuan province. The total length of the N. fulvescens mitogenome is 16 296 bp and contains 13 protein-coding genes, 2 ribosomal RNA genes, 22 transfer RNA genes and a control region, with a base composition of 34.3%A, 29.1%T, 24.2%C and 12.4%G. The nucleotide sequence data of 12 heavy-strand protein-coding genes of N. fulvescens and other 18 rodents were used for mitochondrial genome phylogenetic analyses. Bayesian phylogenetic tree demonstrated the genus Niviventer was embedded within the genus Leopoldamys, although three Niviventer species constituted a monophyletic group. More complete mitochondrial genome sequences are required to illuminate the molecular phylogenetic relationship between Niviventer and Leopoldamys.

Clonal diversity of CTX-M-producing, multidrug-resistant Escherichia coli from rodents

This territory-wide study investigated the occurrence of faecal carriage of extended-spectrum β-lactamase (ESBL)-producing Escherichia coli among wild rodents from the 18 districts in Hong Kong. Individual rectal swabs were obtained from the trapped animals and cultured in plain and selective media. A total of 965 wild rodents [148 chestnut spiny rats (Niviventer fulvescens), 326 Indo-Chinese forest rats (Rattus andamanensis), 452 brown rats (Rattus norvegicus) and 39 black rats (Rattus rattus)] were sampled. ESBL carriage was 0 % in chestnut spiny rats, 0.6 % in Indo-Chinese forest rats, 7.7 % in black rats and 13.9 % in brown rats. Among brown rats, the prevalence of ESBL carriage differed markedly by geographical location: absent in two districts, low (7–10 %) in six districts, moderate (11–19 %) in seven districts and high (21–50 %) in three districts. Nonetheless, there was no correlation between the prevalence of ESBL in brown rats and human population density in the 18 districts. CTX-M-type enzymes were detected in 92.0 % of the ESBL-producing isolates, of which 83.1 % were resistant to three or more non-β-lactam drugs. The CTX-M producing isolates were genetically diverse but a large proportion (47.8 %) were included in six successful clones that are strongly associated with human diseases and CTX-M dissemination, viz. sequence type complex [STC]10/phylogroup A, STC23/phylogroup B1, STC38/phylogroup D, STC155/phylogroup B1, ST405/phylogroup D and ST131/phylogroup B2. In conclusion, our results show that brown rats often carry potentially zoonotic clones of CTX-M producing, multidrug-resistant E. coli. The potential for rats to be a source of CTX-M producing E. coli for humans deserves further consideration.

Clonal diversity of CTX-M-producing, multidrug-resistant Escherichia coli from rodents.

This territory-wide study investigated the occurrence of faecal carriage of extended-spectrum β-lactamase (ESBL)-producing Escherichia coli among wild rodents from the 18 districts in Hong Kong. Individual rectal swabs were obtained from the trapped animals and cultured in plain and selective media. A total of 965 wild rodents [148 chestnut spiny rats (Niviventer fulvescens), 326 Indo-Chinese forest rats (Rattus andamanensis), 452 brown rats (Rattus norvegicus) and 39 black rats (Rattus rattus)] were sampled. ESBL carriage was 0 % in chestnut spiny rats, 0.6 % in Indo-Chinese forest rats, 7.7 % in black rats and 13.9 % in brown rats. Among brown rats, the prevalence of ESBL carriage differed markedly by geographical location: absent in two districts, low (7-10 %) in six districts, moderate (11-19 %) in seven districts and high (21-50 %) in three districts. Nonetheless, there was no correlation between the prevalence of ESBL in brown rats and human population density in the 18 districts. CTX-M-type enzymes were detected in 92.0 % of the ESBL-producing isolates, of which 83.1 % were resistant to three or more non-β-lactam drugs. The CTX-M producing isolates were genetically diverse but a large proportion (47.8 %) were included in six successful clones that are strongly associated with human diseases and CTX-M dissemination, viz. sequence type complex [STC]10/phylogroup A, STC23/phylogroup B1, STC38/phylogroup D, STC155/phylogroup B1, ST405/phylogroup D and ST131/phylogroup B2. In conclusion, our results show that brown rats often carry potentially zoonotic clones of CTX-M producing, multidrug-resistant E. coli. The potential for rats to be a source of CTX-M producing E. coli for humans deserves further consideration.

Molecular prevalence ofTrypanosomaspp. in wild rodents of Southeast Asia: influence of human settlement habitat

This study investigated the molecular prevalence of Trypanosoma lewisi and T. evansi in wild rodents from Cambodia, Lao PDR and Thailand. Between 2008 and 2012, rodents (and shrews) were trapped in nine locations and 616 of these were tested using three sets of primers: TRYP1 (amplifying ITS1 of ribosomal DNA of all trypanosomes), TBR (amplifying satellite genomic DNA of Trypanozoon parasites) and LEW1 (amplifying ITS1 of ribosomal DNA of T. lewisi). Based on the size of the PCR products using TRYP1, 17% were positive for T. lewisi and 1·0% positive for Trypanozoon. Results were confirmed by sequencing PCR products and by using more specific primers (LEW1 and TBR). The specificity of TRYP1 primers, however, failed as rodent DNA was amplified in some instances, giving unexpected product sizes. Using LEW1 primers, 13·3% of the samples were confirmed positive for T. lewisi, both by PCR and sequencing. In Thailand, T. lewisi was found in Rattus tanezumi, R. exulans and Berylmys; in Lao PDR, in R. tanezumi and R. exulans, and in Cambodia in R. tanezumi, R. exulans and R. norvegicus. Using TBR, 1·3% of the samples tested positive for Trypanozoon by PCR and sequencing; T. evansi is the only species of the Trypanozoon subgenus possibly present in wild Asian rodents. These results confirmed its presence in rodents from Thailand (R. tanezumi), Lao PDR (R. tanezumi, R. nitidus) and Cambodia (R. tanezumi, Niviventer fulvescens, Maxomys surifer). Based on the information related to rodent trapping, it was found that rodent species trapped in and around human dwellings had a higher prevalence of T. lewisi infection. R. tanezumi and R. exulans, two synanthropic species, were mainly found infected in this habitat suggesting a role as a reservoir and thus a potential source of T. lewisi for human infection.

Factors influencing dominance structure of common rodent species in Vietnamese tropical forests

It has been shown that the balance between the common rat species belonging to the genera Maxomys and Niviventer in Vietnam regularly changes depending on the geographical latitude. The highest total rate of the genus Niviventer rats (82% of the total catch) has been observed in the northern region (22°0′N) in the Fansipan highland forests (1800–2000 m above the sea level) and has gradually decreased southward to its minimal value (1% of the total catch) in the lowland dipterocarp forests of Ma Da (11°10′N). On the contrary, Ma Da, the southernmost point, displays the highest rate of Maxomys rats, which decreases northward, reaching less than 2% in the Fansipan forests. The ecological advantages of these common genera are associated with the specific features of their origin and establishment. A case study of a particular area, the Cat Tien National Park, has demonstrated the effects of forest structure and the degree of its disturbance in the balance between the three dominant species, namely, the rats Maxomys surifer and Niviventer fulvescens and the squirrel Callosciurus flavimanus. An additional factor that influences the populations of the rats in question in local areas is their interspecific interactions with the rats of the genus Rattus.

Molecular Demonstration ofTrypanosoma evansiandTrypanosoma lewisiDNA in Wild Rodents from Cambodia, Lao PDR and Thailand

In this study, we investigated the molecular evidence of Trypanosoma evansi in wild rodents from Cambodia, Lao PDR and Thailand. Between November 2007 and June 2009, 1664 rodents were trapped at eight sites representative of various ecological habitats. Of those animals, 94 were tested by direct microscopic blood examination, 633 using the Card Agglutination Test for Trypanosomes (CATT/T.evansi) and 145 by Polymerase Chain Reaction (PCR) with two sets of primers: TRYP1 (amplifying ITS1 of ribosomal DNA of all trypanosomes) and TBR (amplifying satellite genomic DNA of Trypanozoon parasites). Using TRYP1, based on the size of the PCR products, 15 samples from the three countries were positive for Trypanosoma lewisi (two were confirmed by sequencing), and three were positive for Trypanozoon (one was confirmed by sequencing and three by TBR primers); the specificity of the primers failed as rodent DNA was amplified in some cases. Using TBR, six samples were positive for Trypanozoon (one was confirmed by sequencing); as T.evansi is the only species of the Trypanozoon sub-genus possibly present in Asian rodents, these results confirmed its presence in rodents from Thailand (Rattus tanezumi) and Cambodia (R.tanezumi, Niviventer fulvescens & Maxomys surifer). Further investigations are necessary to establish the situation in Lao PDR. None of the 16 samples most strongly positive to the CATT proved to be positive for Trypanozoon by PCR. The merits of the CATT for such studies were not confirmed. Studying the urban and rural circulation of these parasites in rodents will enable an evaluation of human exposure and infection risk, as human infections by T.evansi were recently described in India and by T.lewisi in India and Thailand. As sequencing PCR products is expensive, the development of new molecular and serological tools for rodents would be very useful.