Recurrent Occupational Hantavirus Infections Linked to Feeder Rodent Breeding Farm, Taiwan, 2022.

We investigated 2 acute cases and 1 previous case of Seoul hantavirus infection in workers in a feeder rodent breeding farm in Taiwan. Prevalence of hantavirus IgG among the tested feeder rats was 37.5%. Appropriate prevention measures, including using disinfection protocols and personal protective equipment, are crucial to lowering risk.

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.

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.

Seroepidemiological Study of Spotted Fever Group Rickettsiae and Identification of a Putative New Species, Rickesttsia sp. Da-1, in Gongliao, Northeast Taiwan.

Tick-borne spotted fever group (SFG) rickettsioses were neglected in Taiwan. The study reported a seroepidemiological survey of SFG rickettsiae in residents in Gongliao District, Northeast Taiwan. Blood samples were examined for antibodies against SFG rickettsiae by enzyme-linked immunosorbent assay and immunofluorescence assay. Risk factors were assessed using logistic regression. Ticks parasitizing dogs were collected within a 2 km radius from the houses of seropositive participants, and PCR was performed to detect possible tick-borne pathogens. Of 1108 participants, 75 (6.8%) had antibodies against SFG rickettsiae. Residents were more likely to be seropositive if they were older than 65 years, recruited by Dr. Enjoy's Clinic, or resided in Jilin village. A total of 184 ticks including 5 species (Rhipicephalus sanguineus, Rhipicephalus haemaphysaloides, Dermacentor auratus, Haemaphysalis hystricis, Haemaphysalis ornithophila) were collected. Rickettsia spp. were detected in 6.5% (12/184) of ticks. Rickettsia sp. TwKM01 was found in 6 R. sanguineus and 4 R. haemaphysaloides; while Rickettsia sp. TwKM03 was identified in 1 R. sanguineus. Moreover, gene-based pairwise analysis indicated identification of a putative new species, Rickettsia sp. Da-1, in D. auratus. These findings provided evidence of SFG rickettsiae infection in ticks and suggested SFG rickettsiae exposure in the residents.

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.

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.

Human granulocytic anaplasmosis in Kinmen, an offshore island of Taiwan.

BACKGROUND: Human granulocytic anaplasmosis, a tick-borne infection caused by Anaplasma phagocytophilum, has received scant attention, while scrub typhus, a mite-transmitted disease caused by Orientia tsutsugamushi, is the most common rickettsiosis in Taiwan. The clinical presentations of both diseases are characterized by undifferentiated fever, headache and malaise. Moreover, both pathogens have been detected in small mammals that serve as hosts for chiggers and ticks in the wild. The objective of the present study was to investigate whether human granulocytic anaplasmosis occurs in Taiwan. METHODOLOGY/PRINCIPAL FINDINGS: Blood samples from 274 patients suspected of having scrub typhus in Kinmen, an offshore island of Taiwan, in 2011 and 2012 were retrospectively examined by immunofluorescence assays. IgG antibodies reactive with Anaplasma phagocytophilum was found in 31.8% (87/274) of the patients. Paired serology identified 3 patients with human granulocytic anaplasmosis and 8 patients with coinfection with O. tsutsugamushi and A. phagocytophilum. Laboratory tests showed that elevated serum ALT/AST, creatinine, and BUN levels were observed in patients with anaplasmosis and coinfection, but elevated serum CRP levels, thrombocytopenia, and anemia were only observed in coinfected patients. PCR detected A. phagocytophilum 16S rDNA and p44/msp2 in 2 patients. The phylogenetic analysis suggested that the replicons of the 16S rDNA shared high sequence similarity with the reference sequences in the Korea, USA, Japan, and China. The amplicons of p44/msp2 were close to those of the human variants identified in the USA and Japan. CONCLUSIONS: Our findings indicated that A. phagocytophilum infection was prevalent but unrecognized in Taiwan.

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 ticks and associated pathogens in free-ranging Formosan pangolins (Manis pentadactyla pentadactyla).

Chinese pangolins are critically endangered insectivorous mammals distributed in several South and Southeast Asian countries. In recent years, there has been an increase in spread of tick-borne diseases in both humans and animals worldwide. Currently, limited information is available on ticks and associated pathogens infesting pangolins. The objective of the present study was to survey ticks and associated pathogens in the Formosan pangolin population in Southeastern Taiwan. Free-ranging Formosan pangolins captured during ecological survey were examined for the presence of ticks. DNA extracted from these ticks was used to identify the tick species and also to detect the tick-borne pathogens, by molecular methods. In the present study, we found 25% (13/52) of pangolins captured during 2012-2014 infested with ixodid ticks. A total of 21 ticks were collected and 3 species were identified: Haemaphysalis hystricis (14/21), Haemaphysalis formosensis (2/21) and Amblyomma testudinarium (5/21). We detected four different tick-borne pathogens, where one was identical to Anaplasma sp. strain An.H1446 while others showed close resemblance to Rickettsia conorii subsp. caspia A-167, Ehrlichia sp. TC251-2 and Cytauxzoon spp., respectively. The present study is the first survey of ticks infesting the free-ranging Chinese pangolins and pathogens harboured by these ticks. This information is important to know the diversity of ticks and tick-borne pathogens, and its conservation significance to pangolins and other sympatric wildlife. Important future step should be regular surveillance of ticks and tick-borne diseases at human-domestic animals-wildlife interface, which can provide a useful insight into the dynamics of these pathogens and can help control and prevent outbreak of zoonoses.

Prevalence of antibodies against Ehrlichia spp. and Orientia tsutsugamushi in small mammals around harbors in Taiwan.

BACKGROUND: Tick-borne ehrlichiosis and mite-borne scrub typhus represent important emerging zoonotic rickettsial diseases. Although scrub typhus has been recognized by the Taiwanese public health system, information on ehrlichial infections is scarce in Taiwan. In this study, the risk of spread of ectoparasites on rodents through aerial and marine transportation was assessed in international and domestic harbors. Here, we report the first systematic surveillance of seroprevalence against Ehrlichia spp. in small mammals on the main island of Taiwan. METHODS: In total, 1648 small mammals were trapped from 8 international ports, 18 domestic fishing harbors, and 7 local public health centers around Taiwan from November 2004 to December 2008. Sera were analyzed using indirect immunofluorescence assays to detect IgG antibodies against Ehrlichia chaffeensis and Orientia tsutsugamushi. A serum titer of ≧1:80 was considered positive. RESULTS: Antibodies against Ehrlichia spp. and O. tsutsugamushi were detected in 3.28% and 4.92% of small mammals active around harbors, respectively. The seropositive rate against Ehrlichia was higher in northern Taiwan from 2005 to 2008. However, O. tsutsugamushi infections increased in southern Taiwan during this period. The serological evidence of ehrlichial and O. tsutsugamushi infections in all international ports were included in the study. No significant differences were found among the seropositive rates of Ehrlichia spp. and O. tsutsugamushi in small mammals trapped between international and local harbors. CONCLUSIONS: The overall prevalence of Ehrlichia spp. and O. tsutsugamushi infections in small mammals active around harbors was 3.28% and 4.92%, respectively. The results provided serological evidence supporting the potential risks of transporting pathogens through air and maritime traffic. This study highlights serious issues of the emergence and spread of rickettsial diseases in Taiwan. The incidence of human ehrlichiosis requires further investigation.

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.

Bayesian spatial modelling and the significance of agricultural land use to scrub typhus infection in Taiwan.

Scrub typhus is transmitted by the larval stage of trombiculid mites. Environmental factors, including land cover and land use, are known to influence breeding and survival of trombiculid mites and, thus, also the spatial heterogeneity of scrub typhus risk. Here, a spatially autoregressive modelling framework was applied to scrub typhus incidence data from Taiwan, covering the period 2003 to 2011, to provide increased understanding of the spatial pattern of scrub typhus risk and the environmental and socioeconomic factors contributing to this pattern. A clear spatial pattern in scrub typhus incidence was observed within Taiwan, and incidence was found to be significantly correlated with several land cover classes, temperature, elevation, normalized difference vegetation index, rainfall, population density, average income and the proportion of the population that work in agriculture. The final multivariate regression model included statistically significant correlations between scrub typhus incidence and average income (negatively correlated), the proportion of land that contained mosaics of cropland and vegetation (positively correlated) and elevation (positively correlated). These results highlight the importance of land cover on scrub typhus incidence: mosaics of cropland and vegetation represent a transitional land cover type which can provide favourable habitats for rodents and, therefore, trombiculid mites. In Taiwan, these transitional land cover areas tend to occur in less populated and mountainous areas, following the frontier establishment and subsequent partial abandonment of agricultural cultivation, due to demographic and socioeconomic changes. Future land use policy decision-making should ensure that potential public health outcomes, such as modified risk of scrub typhus, are considered.