Parasite infestation patterns differ between ticks and chigger mites on two rodent host species in Taiwan.

Parasites are typically concentrated on a few host individuals, and identifying the mechanisms underlying aggregated distribution can facilitate a more targeted control of parasites. We investigated the infestation patterns of hard ticks and chigger mites on two rodent species, the striped field mouse, Apodemus agrarius, and the lesser ricefield rat, Rattus losea, in Taiwan. We also explored abiotic and biotic factors that were important in explaining variation in the abundance of ticks and chiggers on rodent hosts. Ticks were more aggregated than chiggers on both rodent species. Factors important for the variation in parasitic loads, especially biotic factors, largely differed between ticks and chiggers. Variation partitioning analyses revealed that a larger proportion of variation in chiggers than in ticks can be explained, especially by abiotic factors. If, as proposed, the higher number of parasites in males is due to a larger range area or immunity being suppressed by testosterone, when A. agrarius males host more ticks, they are expected to also host more chiggers, given that chiggers adopt a similar host finding approach to that of ticks. Instead, the similar abundance of chiggers in male and female A. agrarius implies that a large home range or suppressed immunity does not predispose males to inevitably host more parasites. More variations were explained by abiotic than biotic factors, suggesting that controlling practices are more likely to be successful by focusing on factors related to the environment instead of host traits. Our study indicated that the extent of parasitism is rarely determined by a sole factor, but is an outcome of complex interactions among animal physiology, animal behavior, characteristics of parasites, and the environments.

Surveillance of ticks on a tropical island with introduced ungulates.

The abundance of hard ticks can be determined by abiotic factors and the presence of suitable hosts. Since deer represent important hosts for many tick species, it is imperative to investigate whether deer introduction will increase the number of ticks, which can transmit a wide variety of pathogens. The sika deer (Cervus nippon) was introduced to Green Island, Taiwan, to supply velvet antlers, a traditional Chinese medicine. However, they were later released into the wild after a steep decline in antler prices. We conducted surveys for questing ticks, ticks on rodents and shrews, and the fecal pellet groups of ungulates (deer and goats) in 31 transects within 3 habitat types (forest, grassland, and roadside) on Green Island every 2 months in 2019. A total of 5,321 questing ticks were collected. All collected ticks were Haemaphysalis mageshimaensis Saito and Hoogstraal, a species first identified on an island with an abundance of sika deer. Additionally, 48 ticks collected from 126 trapped rodents and shrews were almost invariably Ixodes granulatus (except for 1 larval Haemaphysalis sp.). We did not find a positive correlation between the number of questing ticks and the number of fecal pellet groups, suggesting that factors other than ungulate abundance affect tick abundance. Nevertheless, large populations of questing ticks along some roadsides suggest a high risk of tick-borne diseases to tourists on this tropical island.

The East Indies reptile tick Amblyomma helvolum Koch, 1844 (Acari: Ixodidae), taxonomy, biology and new host records, including the first record of human infestation.

Amblyomma helvolum is a widespread, generalist ectoparasite of reptiles in the oriental region, and has the potential to become highly invasive should it be inadvertently introduced outside its native range through the exotic pet trade. All life stages of A. helvolum are re-characterised morphologically and the first examples of nanism (dwarfism) and gynandromorphy (male and female tissue in one animal) for the species are described. Eighteen new hosts records are presented for A. helvolum, including the first case of human infestation. The taxonomy, distribution, ecology, phenology, disease associations, and invasion biology of the species are also discussed.

Molecular identification of Rickettsia spp. in chigger mites in Taiwan.

The genus Rickettsia is the causative agent of several rickettsial diseases that are primarily transmitted by hard ticks. The occurrence of Rickettsia in chigger mites, which are vectors of scrub typhus in the western Pacific region, has been infrequently investigated. We identified Rickettsia spp. in chiggers collected from small mammals in six counties of Taiwan. Moreover, by capitalising on parallel Rickettsia detections on small mammals and their infested ticks and fleas, we were able to identify Rickettsia spp. that suggested more intimate associations with chigger mites. Rickettsia detection rates in 318 pools of chiggers were 21.7% and 22.3% when based on the ompB and gltA gene, respectively. Overall, we identified six (based on the ompB gene) and eight (gltA gene) Rickettsia species. Approximately half of the sequenced species were most similar to Rickettsia sp. clone MB74-1 (ompB gene) and Rickettsia sp. TwKM02 (gltA gene). Furthermore, both species were either infrequently or never identified in small mammals, ticks and fleas, which suggests that chigger mites might be the primary host of both rickettsiae. Whether both species are pathogenic to humans remains to be studied. They may also be microbial endosymbionts of chigger mites, with their potential effects on the pathogenicity of the aetiologic agent of scrub typhus deserving further investigations.

Commensal Rodent Habitat Expansion Enhances Arthropod Disease Vectors on a Tropical Volcanic Island.

On volcanic islands, the release of animals from predators and competitors can lead to increased body size and population density as well as the expanded habitat use of introduced animals relative to their mainland counterparts. Such alterations might facilitate the spread of diseases on islands when these exotic animals also carry pathogenic agents; however, this has rarely been investigated. The commensal Asian house rat (Rattus tanezumi) is confined to human residential surroundings in mainland Taiwan but can be observed in the forests of nearby Orchid Island, which is a tropical volcanic island. Orchid Island is also a hot spot for scrub typhus, a lethal febrile disease transmitted by larval trombiculid mites (chiggers) that are infected primarily with the rickettsia Orientia tsutsugamushi (OT). We predicted an increase in chigger abundance when rodents (the primary host of chiggers) invade forests from human settlements since soils are largely absent in the latter habitat but necessary for the survival of nymphal and adult mites. A trimonthly rodent survey at 10 sites in three habitats (human residential, grassland, and forest) found only R. tanezumi and showed more R. tanezumi and chiggers in forests than in human residential sites. There was a positive association between rodent and chigger abundance, as well as between rodent body weight and chigger load. Lastly, >95% of chiggers were Leptotrombidium deliense and their OT infection rates were similar among all habitats. Our study demonstrated potentially elevated risks of scrub typhus when this commensal rat species is allowed to invade natural habitats on islands. Additionally, while the success of invasive species can be ascribed to their parasites being left behind, island invaders might instead obtain more parasites if the parasite requires only a single host (e.g., trombiculid mite), is a host generalist (e.g., L. deliense), and is transferred from unsuitable to suitable habitats (i.e., human settlements on the mainland to forests on an island).

Revisiting the Pneumocystis host specificity paradigm and transmission ecology in wild Southeast Asian rodents.

Pneumocystis fungi are opportunistic parasites of mammalian lungs whose evolution, ecology and host specificity in natural host populations remain poorly understood and controversial. Using an extensive collection of 731 lung samples from 27 rodent species sampled in five Southeast Asian countries, and nested PCR amplification of mitochondrial and nuclear genes, we investigated the host specificity and genetic structure of Pneumocystis lineages infecting wild rodents. We also identified the rodent species playing a central role in the transmission of these parasites using network analysis and centrality measurement and we characterized the environmental conditions allowing Pneumocystis infection in Southeast Asia using generalized linear mixed models. Building upon an unprecedented Pneumocystis sampling from numerous rodent species belonging to closely related genera, our findings provide compelling evidence that the host specificity of Pneumocystis lineages infecting rodents is not restricted to a single host species or genus as often presented in the literature but it encompasses much higher taxonomic levels and more distantly related rodent host species. The phylogenetic species status at both mitochondrial and nuclear genetic markers of at least three new Pneumocystis lineages, highly divergent from Pneumocystis species currently described, is also suggested by our data. Our models show that the probability of Pneumocystis infection in rodent hosts is positively correlated to environmental variables reflecting habitat fragmentation and landscape patchiness. Synanthropic and habitat-generalist rodents belonging to the Rattus, Sundamys and Bandicota genera played a role of bridge host species for Pneumocystis spreading in these heterogeneous habitats, where they can reach high population densities. These are critical findings improving our understanding of the ecology of these enigmatic parasites and the role played by cospeciation and host switches in their evolution. Our results also confirmed the role of land-use change and habitat fragmentation in parasite amplification and spillover in rodents.

Bigger doesn't mean bolder: behavioral variation of four wild rodent species to novelty and predation risk following a fast-slow continuum.

BACKGROUND: Understanding how wild species respond to novel situations with associated risk can provide valuable insights for inter-specific behavioral variation and associations with pace-of-life (POL). Rodents, a globally distributed and diverse taxonomic group, have been the subjects of countless studies emulating risky situations. Controlled laboratory experiments with a focus on wild-caught species provide the opportunity to test fine-scale behavioral responses to contexts of risk with ecological implications. For example, assessing the importance of predator cues eliciting antipredator responses, as well as whether wild rodents embody behavioral plasticity and repertoires, illustrated by habituation and variation in behavioral traits, respectively. RESULTS: In this comparative study, we examined multiple behavioral responses of four rodent species in eastern Taiwan (three native species Mus caroli, Apodemus agrarius, Rattus losea, and one invasive, Rattus exulans) exposed to an unfamiliar microenvironment and novel cue from an allopatric predator, the leopard cat (Prionailurus bengalensis). All wild-caught animals were subjected to two consecutive nights of experimental trials in a laboratory setting. Behavioral responses to a novel situation during the first trial differed between species; smaller species investing more time in non-defensive behaviors compared to the larger species. More specifically, the smaller species M. caroli and A. agrarius allocated more time to exploration and foraging, whereas the larger rat species R. exulans and R. losea spent more time motionless or concealing. During the second trial, the addition of leopard cat cues did not elicit antipredator behaviors, but rather, rodents were found to exhibit increased non-defensive behaviors, specifically foraging efforts. CONCLUSIONS: Our results suggest that these four species do largely follow a behavioral fast-slow continuum with the two smaller mice species demonstrating increased boldness in a novel context compared to the larger rat species. Also, the wild populations of rodents in eastern Taiwan may be naïve to leopard cats. Finally, the rodents in our study demonstrated habituation to the microenvironment, indicating they possess adaptive capacity.

Molecular detection of Rickettsia species and host associations of Laelaps mites (Acari: Laelapidae) in Taiwan.

Various rickettsiae have recently been detected in Laelaps mites (Acari: Laelapidae), which are common ectoparasites of rodents; however, investigations on this topic remain very scarce, particularly in Asia. In the present study, shrews and rodents were trapped from 2006 to 2010 in eight lowland regions of Taiwan (< 500 m in elevation) to collect associated Laelaps mites, from which Rickettsia-a group of emerging pathogens-were detected and identified by assaying the gltA and ompB genes. A total of 853 Laelaps mites of at least four species were collected from a sample of 1004 small mammals that included one shrew and 10 rodent species. Rattus losea was the most common species (44.9% of total hosts) and hosted the highest percentage of mites (76.6% of total mites). Laelaps nuttalli was the most abundant mite species (51.7% of total mites), followed by Laelaps echidninus (24.2%), Laelaps sedlaceki (23.1%), and Laelaps myonyssognathus (0.2%). Notably, Rickettsia species with the highest similarity to spotted fever group (SFG) rickettsiae were identified from seven of the 72 pools of Laelaps mites. The presence of SFG rickettsiae in hematophagous Laelaps mites, particularly including species that are closely associated with commensal rodents in frequent contact with humans, calls for further investigation on the competence of Laelaps mites in transmitting rickettsiae.

First record of the sea snake tick Amblyomma nitidum Hirst and Hirst, 1910 (Acari: Ixodidae) from Taiwan.

The sea snake tick (Amblyomma nitidum) is a host specialist of snakes in the genus Laticauda and is one of the few ticks which could be regarded as semi-marine. Yet despite the attention this species has received due to its bizarre ecology, its distribution remains poorly known as geographic records of its occurrence through the Asia-Pacific are highly fragmentary. For the first time this species is recorded from Taiwan based on specimens collected from the yellow-lipped sea krait (Laticauda colubrina).

Invasive plants facilitated by socioeconomic change harbor vectors of scrub typhus and spotted fever.

BACKGROUND: Ecological determinants of most emerging vector-borne diseases are understudied, particularly for neglected tropical disease. Moreover, although socioeconomic impacts can have significant downstream effects on human risks to vector-borne diseases via a change in land cover, particularly facilitating the invasion of exotic plants, related studies remains very scarce. Scrub typhus and spotted fever are neglected diseases emerging around the globe and are transmitted by chigger mites and ticks infective of Orientia tsutsugamushi and Rickettsia spp., respectively, with small mammals as the primary hosts of both vectors. METHODOLOGY/PRINCIPAL FINDINGS: We investigated how invasions of the plant Leucaena leucocephala caused by widespread abandonment of farmlands driven by industrialization affected abundance of chiggers and ticks in Penghu Island, Taiwan. We determined ectoparasite abundance by trapping small mammals in three types of habitats (invasion site, agricultural field, human residential) every two months for a year. Based on ectoparasite burdens, invasion sites harbored more chiggers and ticks than the other two habitats. Furthermore, hosts maintained higher burdens of both vectors in early winter and burdens of chiggers were more stable across seasons in invasion sites, suggesting that sites with invasive plants could be a temporary refuge for both vectors and might help mitigate the negative influence of unfavorable climate. Infective rates of O. tsutsugamushi in chiggers and Rickettsia in ticks were also consistently not lower in invasion sites. Top soil temperature and relative humidity were similar across the three habitats, but invasion sites contained more of the rat Rattus losea, on which chiggers and ticks were more engorged than those from the most commonly trapped species (Suncus murinus shrew), indicating that abundance of the host R. losea instead of microclimate might better determine the abundance of both vectors. CONCLUSIONS/SIGNIFICANCE: This study highlights an important but largely neglected issue that socioeconomic change can have unexpected consequences for human health induced particularly by invasive plants, which could become a hotspot for emerging infectious diseases but usually are very hard to be eradicated. In the future, a more comprehensive approach that integrates socio-economics, land use, exotic species, and human health should be considered to fully understand potential emergence of vector-borne diseases.

Fleas of Shrews and Rodents in Rural Lowland Taiwan.

Fleas transmit a variety of pathogens to humans but are relatively understudied in comparison to mosquitoes and ticks, including in Taiwan, where fleas in rural lowlands have never been systematically surveyed. In total, 700 fleas of four species were collected from 1,260 shrews and rodents at nine counties across lowland Taiwan. Nosopsyllus nicanus Jordan (Siphonaptera: Ceratophyllidae) and Xenopsylla cheopis Rothschild (Siphonaptera: Pulicidae) were the most abundant flea species (79.0 and 14.6% of total fleas, respectively); the former was largely limited to the islets, while the latter was restricted to the Taiwan main island. Rattus losea Swinhoe (Rodentia: Muridae) was the most common small mammal species (49.3% of total) and hosted the majority of fleas (88.3% of total). Five Rickettsia spp., including Rickettsia conorii Brumpt (Rickettsiales: Rickettsiaceae), Rickettsia felis Bouyer et al. Rickettsia japonica Uchida, Rickettsia raoultii Mediannikov, and Rickettsia rickettsii Brumpt or closely related species, were identified from 67 individually assayed fleas based on ompB and gltA genes. Rickettsia felis, mainly transmitted by fleas, was detected in one X. cheopis in southern Taiwan where a confirmed human case of infection with R. felis has been reported. The presence of R. felis, along with the other four tick-borne Rickettsia spp., demonstrates that a variety of rickettsiae circulate in rural lowland Taiwan and could pose risks to human health.

First molecular detection of Anaplasma phagocytophilum in the hard tick Rhipicephalus haemaphysaloides in Taiwan.

Anaplasma phagocytophilum is transmitted mainly by hard ticks and can cause potentially fatal granulocytic anaplasmosis in humans, but its occurrence in ticks in Taiwan has never been investigated although this pathogen has been detected in Taiwanese rodents before. Ticks collected from small mammals in Hualien, eastern Taiwan, were assayed for Anaplasma infections; infections of Rickettsia and Apicomplexa protozoans were also studied. Of the 270 individually assayed Rhipicephalus haemaphysaloides ticks, A. phagocytophilum was identified in a nymphal tick. Parasites most similar to Anaplasma bovis, Rickettsia rickettsii, Rickettsia sp. TwKM01, and at least seven apicomplexan species (including genera Cryptosporidium, Hepatozoon, and Theileria) were also identified. This study shows that A. phagocytophilum does occur in the hard tick in Taiwan, although whether R. haemaphysaloides can vector this pathogen remains to be determined. This work also reveals a high diversity of tick-borne bacteria and protozoans circulating in a small region and calls for further research on their potential risks for human health.

Tick-borne pathogens in ticks collected from birds in Taiwan.

BACKGROUND: A variety of human diseases transmitted by arthropod vectors, including ticks, are emerging around the globe. Birds are known to be hosts of ticks and can disperse exotic ticks and tick-borne pathogens. In Taiwan, previous studies have focused predominantly on mammals, leaving the role of birds in the maintenance of ticks and dissemination of tick-borne pathogens undetermined. METHODS: Ticks were collected opportunistically when birds were studied from 1995 to 2013. Furthermore, to improve knowledge on the prevalence and mean load of tick infestation on birds in Taiwan, ticks were thoroughly searched for when birds were mist-netted at seven sites between September 2014 and April 2016 in eastern Taiwan. Ticks were identified based on both morphological and molecular information and were screened for potential tick-borne pathogens, including the genera Anaplasma, Babesia, Borrelia, Ehrlichia and Rickettsia. Finally, a list of hard tick species collected from birds in Taiwan was compiled based on past work and the current study. RESULTS: Nineteen ticks (all larvae) were recovered from four of the 3096 unique mist-netted bird individuals, yielding a mean load of 0.006 ticks/individual and an overall prevalence of 0.13%. A total of 139 ticks from birds, comprising 48 larvae, 35 nymphs, 55 adults and one individual of unknown life stage, were collected from 1995 to 2016, and 11 species of four genera were identified, including three newly recorded species (Haemaphysalis wellingtoni, Ixodes columnae and Ixodes turdus). A total of eight tick-borne pathogens were detected, with five species (Borrelia turdi, Anaplasma sp. clone BJ01, Ehrlichia sp. BL157-9, Rickettsia helvetica and Rickettsia monacensis) not previously isolated in Taiwan. Overall, 16 tick species of five genera have been recorded feeding on birds, including nine species first discovered in this study. CONCLUSION: Our study demonstrates the paucity of information on ticks of birds and emphasizes the need for more research on ticks of birds in Taiwan and Southeast Asia. Moreover, some newly recorded ticks and tick-borne pathogens were found only on migratory birds, demonstrating the necessity of further surveillance on these highly mobile species.

Correction: Significance of major international seaports in the distribution of murine typhus in Taiwan.

[This corrects the article DOI: 10.1371/journal.pntd.0005430.].

Significance of major international seaports in the distribution of murine typhus in Taiwan.

BACKGROUND: International seaports are hotspots for disease invasion and pathogens can persist in seaports even after ports are abandoned. Transmitted by fleas infected by Rickettsia typhi, murine typhus, a largely neglected and easily misdiagnosed disease, is known to occur primarily in large seaports. However, the significance of seaports in the occurrence of murine typhus has never been validated quantitatively. METHODOLOGY/PRINCIPAL FINDINGS: We studied the spatial distribution of murine typhus, a notifiable disease, in Taiwan. We investigated whether risk of infection was correlated with distance to international seaports and a collection of environmental and socioeconomic factors, using a Bayesian negative binomial conditionally autoregressive model, followed with geographically weighted regression. Seaports that are currently in use and those that operated in the 19th century for trade with China, but were later abandoned due to siltation were analyzed. A total of 476 human cases of murine typhus were reported during 2000-2014 in the main island of Taiwan, with spatial clustering in districts in southwest and central-west Taiwan. A higher incidence rate (case/population) was associated with a smaller distance to currently in-use international seaports and lower rainfall and temperature, but was uncorrelated with distance to abandoned ports. Geographically weighted regression revealed a geographic heterogeneity in the importance of distance to in-use seaports near the four international seaports of Taiwan. CONCLUSIONS/SIGNIFICANCE: Our study suggests that murine typhus is associated with international seaports, especially for those with large trading volume. Thus, one of the costs of global trade in Taiwan might be elevated risks of murine typhus. Globalization has accelerated the spread of infectious diseases, but the burden of disease varies geographically, with regions surrounding major international seaports warranting particular surveillance.

Surveillance of potential hosts and vectors of scrub typhus in Taiwan.

BACKGROUND: Scrub typhus is a lethal infectious disease vectored by larval trombiculid mites (i.e. chiggers) infected with Orientia tsutsugamushi (OT) and recent decades have witnessed an emergence of scrub typhus in several countries. Identification of chigger species and their vertebrate hosts is fundamental for the assessment of human risks to scrub typhus under environmental changes, but intensive and extensive survey of chiggers and their hosts is still lacking in Taiwan. METHODS: Chiggers were collected from shrews and rodents in nine counties of Taiwan and were assayed for OT infections with nested polymerase chain reaction (PCR). PCR products were further sequenced to reveal probable OT strains. Rodents were assessed for OT exposure by immunofluorescent antibody assay. Lastly, incidence rate of scrub typhus in each county was associated with loads and prevalence of chigger infestations, seropositivity rate in rodents, and OT positivity rate in chiggers. RESULTS: Rattus losea was the most abundant (48.7% of 1,285 individuals) and widespread (occurred in nine counties) small mammal species and hosted the majority of chiggers (76.4% of 128,520 chiggers). Leptotrombidium deliense was the most common (64.9% of all identified chiggers) and widespread (occurred in seven counties) chigger species but was replaced by Leptotrombidium pallidum or Leptotrombidium scutellare during the cold seasons in two counties (Matsu and Kinmen) where winter temperatures were lower than other study sites. Seropositivity rate for OT exposure in 876 assayed rodents was 43.0% and OT positivity rate in 347 pools of chiggers was 55.9%, with 15 OT strains identified in the 107 successfully sequenced samples. Incidence rate of scrub typhus was positively correlated with chigger loads, prevalence of chigger infestations, seropositivity rate but not OT positivity rate in chiggers. CONCLUSIONS: Our study reveals R. losea as the primary host for chiggers and there exists a geographical and seasonal variation in chigger species in Taiwan. It also emphasizes the importance of recognition of chigger vectors and their vertebrate hosts for a better prediction of human risks to scrub typhus under rapid environmental changes.

A Checklist of Chigger Mites (Acari: Trombiculidae and Leeuwenhökiidae) From Taiwan, With Descriptions of Three New Species.

Scrub typhus is a lethal human disease transmitted by larval trombiculid mites (i.e., chiggers) that have been infected with the rickettsia Orientia tsutsugamushi. In total, 21 chigger species are known from Taiwan. We update the checklist of chiggers of Taiwan based on an intensive survey of shrew and rodent hosts in grasslands and agricultural fields in lowland Taiwan, coupled with surveys of forests in one mountainous site and an opportunistic examination of submitted host specimens. Three new species of chiggers, Gahrliepia (Gateria) lieni sp. n., Gahrliepia (Gateria) minuta sp. n., and Gahrliepia (Gateria) yilanensis sp. n., as well as 23 newly recorded chigger species, were discovered. Accordingly, recorded chigger species of Taiwan more than doubled from 21 to 47 species. Two new species and nine newly recorded chigger species were discovered in forests in one mountainous site in northeastern Taiwan, suggesting that many more chigger species may be uncovered, particularly in mountainous Taiwan. Further studies should also investigate O. tsutsugamushi infection in different chigger species to assess its risks to human health.

Widespread Rickettsia spp. Infections in Ticks (Acari: Ixodoidea) in Taiwan.

Ticks are second to mosquitoes as the most important disease vectors, and recent decades have witnessed the emergence of many novel tick-borne rickettsial diseases, but systematic surveys of ticks and tick-borne rickettsioses are generally lacking in Asia. We collected and identified ticks from small mammal hosts between 2006 and 2010 in different parts of Taiwan. Rickettsia spp. infections in ticks were identified by targeting ompB and gltA genes with nested polymerase chain reaction. In total, 2,732 ticks were collected from 1,356 small mammals. Rhipicephalus haemaphysaloides Supino (51.8% of total ticks), Haemaphysalis bandicota Hoogstraal & Kohls (28.0%), and Ixodes granulatus Supino (20.0%) were the most common tick species, and Rattus losea Swinhoe (44.7% of total ticks) and Bandicota indica Bechstein (39.9%) were the primary hosts. The average Rickettsia infective rate in 329 assayed ticks was 31.9% and eight Rickettsia spp. or closely related species were identified. This study shows that rickettsiae-infected ticks are widespread in Taiwan, with a high diversity of Rickettsia spp. circulating in the ticks. Because notifiable rickettsial diseases in Taiwan only include mite-borne scrub typhus and flea-borne murine typhus, more studies are warranted for a better understanding of the real extent of human risks to rickettsioses in Taiwan.

High prevalence of Rickettsia spp. infections in small mammals in Taiwan.

Surveillance for Rickettsia spp. is urgently needed due to the recent emergence of many novel rickettsioses around the globe, but previous studies in Taiwan have been limited to small areas and no investigation of infections in vertebrate hosts has ever been attempted. We surveyed rickettsial infections systematically in small-mammal hosts trapped between 2006 and 2010 throughout Taiwan. Fragments of ompB and gltA genes in the liver, spleen, and kidney of mammals were targeted by nested polymerase chain reaction. We trapped 1375 individuals of 10 species, among which Rattus losea was the most common (54.6%), followed by Suncus murinus (20.6%) and Mus caroli (10.6%). The overall rate of Rickettsia infections in the liver, spleen, or kidney of 309 assayed small mammals was 60.5%, with a rate of infection ≥50% for each mammal species. DNA nucleotide sequences of 184 successfully sequenced genes were most similar to nine Rickettsia species: Rickettsia conorii, R. felis, R. japonica, R. raoultii, R. rickettsii, Rickettsia sp. IG-1, Rickettsia sp. TwKM01, Rickettsia sp. TwKM02, and R. typhi. Our results suggest that several novel Rickettsia spp. are common and widespread across various habitats throughout Taiwan and suggest the need for further study of emerging rickettsioses in Taiwan.

Delimitation of a continuous morphological character with unknown prior membership: application of a finite mixture model to classify scapular setae of Abacarus panticis.

Unambiguous classification is a prerequisite for the study of polymorphism, but accurate delimitation of continuous morphological characters can be challenging. Finite mixture modeling is a rigorous and flexible approach for delimiting continuous variables with unknown prior membership, but its application to morphological studies remains limited. In this study, the lengths of scapular setae of the eriophyoid mite Abacarus panticis Keifer collected from 18 sites in Taiwan were used as an example to evaluate the eligibility of finite mixture models. We then tested the hypothesis that longer scapular setae can facilitate dispersal. Lastly, we investigate morphological variation in various seta morphs by geometric morphometric techniques. Finite mixture models can satisfactorily classify scapular setae of A. panticis into long and short seta morphs. Abacarus panticis of the long morph only occurred in five sites whereas the short seta morph existed in all study sites. Geometric morphometric analyses revealed a more elongated coxal area in individuals of long morph than in those of short morph. Because the short morph is more widespread in geographical distribution than the long morph, longer scapular setae seem unlikely a specialized adaptation for dispersal. Further studies should capitalize on the finite mixture model in the delimitation of continuous morphological characters.