Molecular identification and genetic diversity of Bartonella spp. in 24 bat species from Thailand

Understanding zoonotic pathogens and risk factors from wildlife in Southeast Asia: a systematic literature review

The COVID-19 pandemic has demonstrated the significance of the human-animal interface in the emergence of zoonotic diseases, with wildlife serving as an important source of infection. A better understanding of the specific pathogens and mechanisms involved is vital to prepare against future outbreaks, especially in Southeast Asia, a hotspot for zoonotic diseases. This paper reviews the published literature on wildlife zoonoses in this region from 2012 to 2022. The results show a diverse range of potential zoonotic pathogens and the widespread occurrence of zoonotic diseases from wildlife. Drivers of zoonotic pathogen spillover include (i) environmental factors (e.g. animal habitat disruption, environmental conditions, exposure to contaminated water/food/soil), (ii) animal factors (e.g. movement patterns, age-related susceptibility), (iii) human factors (e.g. lack of awareness, poor hygiene practices, age, gender and income) and (iv) human-animal-environmental interface factors (e.g. close contact between humans and animals, exposure through visiting animals and presence of vectors). The diverse drivers of zoonoses in Southeast Asia put its communities at risk for infection. To mitigate these risks, global health efforts should consider adopting a One Health approach to foster collaboration across human, animal, and wildlife health sectors. This could involve educating communities on safe animal interactions and improving disease surveillance.

Mitochondrial genome characterization of a Reticulinasus sp. (Argasidae: Ornithodorinae) parasitizing bats in Thailand

BACKGROUND

Second only to mosquitoes, ticks (Acari: Ixodida) are significant blood-feeding ectoparasites and vectors of numerous pathogens affecting both animals and humans. Despite bats serving as hosts to various tick species, they remain relatively understudied due to their nocturnal behavior and laborious capture procedures. Soft ticks in particular display diverse ecological behaviors, inhabiting bat roosts, caves, and occasionally human dwellings. This overlap in habitats suggests soft ticks may play a critical role as vectors of zoonotic pathogens. In Southeast Asia, research on soft ticks has primarily focused on island nations, with limited studies on bat-associated ticks in Thailand. This study aimed to examine the identity and distribution of bat ticks in Thailand.

METHODS

Bats were captured across ten provinces in Thailand between 2018 and 2023. Ticks were removed from the bats' skin and identified through morphological examination using a stereomicroscope, with molecular confirmation. Scanning electron micrographs were recorded. Prevalence, mean abundance, and mean intensity of tick infestations were calculated. The mitochondrial genomes of the ticks were sequenced, annotated, and subjected to phylogenetic analysis.

RESULTS

A total of 1031 bats, representing 7 families, 11 genera, and 28 species, were captured. Tick infestations were found in 34 bats (3.30%), specifically in two species: Craseonycteris thonglongyai (33/139, 23.74%) and Eonycteris spelaea (1/2, 50%). All ticks were in the larval stage. Basic local alignment search tool for nucleotide (BLASTN) searches using 16S rRNA (425 bp) and COI (825 bp) sequences, along with Barcode of Life Database (BOLD) database queries, revealed the highest similarity to tick in the genus Reticulinasus found on bats in Zambia. The mitochondrial genomes of ticks collected from C. thonglongyai and E. spelaea were 14,433 bp and 14,439 bp in length, respectively, and contained 13 protein-coding genes, 22 tRNA genes, and 2 rRNA genes. Phylogenetic analysis placed these ticks within the Reticulinasus clade, with strong support indicated by high bootstrap values.

CONCLUSIONS

This study identified Reticulinasus sp. infestations on C. thonglongyai and E. spelaea bats, marking the first report of soft ticks in bats from Thailand, with potential implications for zoonotic disease transmission.

An integrative taxonomic approach reveals two putatively novel species of phlebotomine sand fly (Diptera: Psychodidae) in Thailand

BACKGROUND

The subfamily Phlebotominae comprises 1028 species of sand fly, of which only 90 are recognized as vectors of pathogenic agents such as Trypanosoma, Leishmania, and Bartonella. In Thailand, leishmaniasis-a sand fly-borne disease-is currently endemic, with 36 documented sand fly species. However, many cryptic species likely remain unidentified. To improve our understanding of the distribution, habitat preferences, and role in disease transmission of these sand flies, further research is necessary.

METHODS

Sand flies were collected using CDC light traps from 13 locations across four provinces in Thailand between October 2022 and October 2023. Initially, species identification was based on morphological characteristics, employing identification keys, and subsequently confirmed through mitochondrial cytochrome oxidase c subunit I (COI) and cytochrome b (Cytb) sequencing. Species identities were verified using BLASTN and BOLD searches. Species delimitation was conducted using Automatic Barcode Gap Discovery (ABGD) and Assemble Species by Automatic Partitioning (ASAP) with three substitution models. Additionally, intraspecific and interspecific genetic variation, neutrality tests (including Tajima's and Fu and Li's D* tests), phylogenetic analyses, and TCS haplotype network analysis were performed using the obtained sequences.

RESULTS

A total of 3693 phlebotomine sand flies were collected, with 2261 (61.22%) identified as female. Integrative analyses combining morphological data, BLASTN searches, phylogenetic assessments, and species delimitation confirmed the identification of four genera: Sergentomyia, Grassomyia, Phlebotomus, and Idiophlebotomus, encompassing 12 species: Sergentomyia anodontis, Se. sylvatica, Se. perturbans, Se. barraudi, Se. hivernus, Se. khawi, Se. siamensis, Grassomyia indica, Phlebotomus barguesae, Ph. stantoni, Idiophlebotomus asperulus, and Id. longiforceps. Furthermore, molecular analysis revealed cryptic and complex species, including two putatively novel species, Se. sp. 1 and Se. sp. 2, as well as a unique haplotype.

CONCLUSIONS

This study, which integrated genetic and morphological identification techniques, identified 12 sand fly species and unveiled cryptic and complex species, including two putatively novel species (Se. sp. 1 and Se. sp. 2) and a unique haplotype. The findings underscore the utility of mitochondrial genes, combined with species delimitation methodologies, as reliable approaches for identifying diverse sand fly species.

Cave-dwelling phlebotomine sand flies (Diptera: Psychodidae: Phlebotominae) in Thailand: population composition and pathogen detection of Bartonella and Trypanosoma

BACKGROUND

Leishmaniasis is an emerging vector-borne disease that occurs in Thailand. Although Leishmania (Mundinia) parasites, the causative agents of the disease have been identified, the vectors of the disease remain unidentified. In the present study, we collected sand flies from three caves located in endemic areas of leishmaniasis, including Lampang and Chiang Rai in northern Thailand, and Songkhla in southern Thailand.

METHODS

Female sand flies were identified on the basis of morphological characteristics and confirmed by cytochrome c oxidase subunit I (COI) sequencing. Sand fly DNA samples were screened for Leishmania, Trypanosoma, and Bartonella DNA by polymerase chain reaction (PCR) on the basis of the ITS1 region of the ribosomal RNA (rRNA), SSU rRNA, and gltA genes, followed by phylogenetic relationships and haplotype diversity analysis.

RESULTS

A total of 557 sand flies were identified, comprising four genera (Sergentomyia, Phlebotomus, Grassomyia, and Idiophlebotomus) and 11 species. Molecular detection of pathogens demonstrated that Leishmania DNA was not detected. However, Trypanosoma DNA was detected in 11 samples of Phlebotomus mascomai from Lampang (7 for T. noyesi), Se. anodontis from Chiang Rai (1 each for T. noyesi and Trypanosoma sp.), and Se. khawi from Songkhla (2 for Trypanosoma sp.). Bartonella DNA was detected in 16 samples of Se. anodontis and Se. barraudi s.l. from Chiang Rai, Se. anodontis from Lampang, and Se. khawi from Songkhla. The novel Bartonella sp. detected in Thai sand flies was phylogenetically related to Bartonella sp. from bats. Genetic diversity analysis showed high haplotype diversity in both Trypanosoma parasites and Bartonella bacteria.

CONCLUSIONS

The data from the present study indicate that phlebotomine sand flies could be potential vectors of zoonotic diseases caused by Trypanosoma sp. and Bartonella sp. To our knowledge, this is the first report of the natural infection of Bartonella associated with bats in Thailand, and the presence of T. noyesi and amphibian trypanosomes. However, further investigation is required to elucidate and enhance the understanding of potential vectors and transmission dynamics of pathogens in Thailand, particularly with regard to different seasonality, habitats, and host ranges.

From host individual traits to community structure and composition: Bartonella infection insights

BACKGROUND

Phylogeny, combined with trait-based measures, offers insights into parasite sharing among hosts. However, the specific traits that mediate transmission and the aspects of host community diversity that most effectively explain parasite infection rates remain unclear, even for the Bartonella genus, a vector-borne bacteria that causes persistent blood infections in vertebrates.

METHODS

This study investigated the association between rodent host traits and Bartonella infection, as well as how rodent community diversity affects the odds of infection in the Atlantic Forest, using generalized linear models. Additionally, we assessed how host traits and phylogenetic similarities influence Bartonella infection among mammal species in Brazil. To this end, rodents were sampled from ten municipalities in Rio de Janeiro, southeastern Brazil. Then, we calculated several diversity indices for each community, including Rényi's diversity profiles, Fisher's alpha, Rao's quadratic entropy (RaoQ), Functional Diversity (FDis), Functional Richness (FRic), and Functional Evenness (FEve). Finally, we compiled a network encompassing all known interactions between mammal species and Bartonella lineages recorded in Brazil.

RESULTS

We found no significant relationship between diversity indices and the odds of Bartonella infection in rodent communities. Furthermore, there was no statistical support for the influence of individual-level traits (e.g., body length, sex, and age) or species-level ecological traits (e.g., locomotor habitat, dietary guild, and activity period) on Bartonella infection in rodents. A country-scale analysis, considering all mammal species, revealed no effect of host traits or phylogeny on Bartonella infection.

CONCLUSIONS

This study highlighted wild mammals that share Bartonella lineages with livestock, synanthropic, and domestic animals, underscoring the complexity of their maintenance cycle within the One Health framework. A key question arising from our findings is whether molecular host-cell interactions outweigh host body mass and ecological traits in influencing Bartonella infection, potentially opening new avenues for understanding host-parasite relationships and infection ecology.

Diversity of questing ticks and prevalence of tick-associated pathogens in Khao Kheow-Khao Chomphu Wildlife Sanctuary, Chon Buri, Thailand

Ixodid ticks are important vectors for tick-borne diseases distributed worldwide, including Thailand. Recreation areas within wildlife habitats are considered high-risk zones for tick exposure and tick-borne disease in humans. The study aimed to determine seasonal variations in tick diversity and pathogen prevalence in Khao Kheow-Khao Chomphu Wildlife Sanctuary, Chon Buri, Thailand. From November 2021 to March 2023, a total of 1331 immature ticks were collected by dragging. The proportion of collected larvae was highest in February 2022, while the number of collected nymphs peaked in December 2021. Seven tick species were molecularly identified: Haemaphysalis lagrangei, H. wellingtoni, H. shimoga, H. obesa, Dermacentor auratus, Rhipicephalus microplus, and Amblyomma integrum. Of 80 tick pools, Anaplasma, piroplasms (Babesia and Theileria), Bartonella, and Rickettsia were detected in 10% (8/80), 3.75% (3/80), 1.25% (1/80), and 3.75% (3/80) of tick pools, respectively. Phylogenetic analysis grouped the newly generated sequences in the clades of Anaplasma bovis, Babesia gibsoni, Theileria cervi, Bartonella henselae, and Rickettsia montanensis. A seasonal pattern of pathogen appearance was detected during November to February, the cool season in Thailand. Based on our results indicating the highest peak of immature ticks and prevalence of pathogens, visitors should take precautions to avoid tick exposure during this season.

Development of a quadruplex PCR amplicon next generation sequencing assay for detection and differentiation of Bartonella spp

The genus Bartonella includes a group of species that are associated with a wide range of mammalian species, including human. It is challenging to detect all Bartonella species using a single molecular target due to its high genetic diversity. To solve this issue, we developed a quadruplex PCR amplicon sequencing assay using next-generation sequencing (NGS) technology for the detection and differentiation of Bartonella species. Our objective was to obtain the specific sequences of a minimum of two of the four target genes as confirmation of the identity of a particular Bartonella species using the assay. Four pairs of primers targeting specific regions on gltA, groEL, rpoB, and ssrA were evaluated for their capability of differentiating Bartonella species individually and collectively by performing singular PCR amplicon sequencing and quadruplex PCR amplicon sequencing. Using the quadruplex PCR amplicon sequencing, 24 Bartonella reference species were tested, all of which were successfully differentiated by at least two targets. Bartonella species were accurately identified from the artificially mixed DNA templates developed to simulate coinfections. The limit of detection was determined to be 1 fg based on testing a series of 10-fold dilutions of DNA from the Bartonella species. Testing of high DNA concentrations of 19 non-Bartonella species showed high specificity with none of the non-Bartonella species misclassified as Bartonella. Finally, the assay was evaluated by testing DNA extracts from field-collected body lice (Pediculus humanus humanus) and Norway rats (Rattus norvegicus): Bartonella quintana was detected and confirmed by three targets in the lice and Bartonella tribocorum was detected and confirmed by two targets in the rats. These results demonstrated that Bartonella species could be accurately and rapidly detected and differentiated into different tissue types using the quadruplex sequencing assay.

Complete mitochondrial genome analyses confirm that bat Polychromophilus and ungulate Plasmodium constitute a distinct clade independent of other Plasmodium species

In recent phylogenetic studies, bat Polychromophilus and ungulate Plasmodium, two relatively understudied haemosporidian parasites within the Apicomplexa phylum, have often been overlooked. Instead, the focus has been primarily on haemosporidian parasites in primates, rodents, and birds. Several phylogenetic analyses of bat Polychromophilus have relied on limited datasets and short informative DNA sequences. As a result of these inherent limitations, the substantiation of their evolutionary stance has encountered a diminished degree of robust validation. This study successfully obtained complete mitochondrial genome sequences from 11 Polychromophilus parasites originating from Hipposideros gentilis and Myotis siligoensis bats for the first time. Additionally, the authors have sequenced the apicoplast caseinolytic protease C genes from Polychromophilus murinus and a potentially new Polychromophilus species. These mitochondrial genomes range in length from 5994 to 6001 bp and consist of three protein-coding genes (PCGs), seven small subunit ribosomal RNA genes (SSU rRNA), 12 large subunit ribosomal RNA genes (LSU rRNA), and seven miscellaneous RNA genes. Phylogenetic analyses using Bayesian Inference and Maximum Likelihood methods indicated robust support for the grouping of ungulate Plasmodium and bat Polychromophilus in a single clade separate from other Plasmodium spp., confirming previous reports, albeit with stronger evidence in this study. The divergence between Polychromophilus in bats and Plasmodium in ungulates occurred approximately 29.61 to 55.77 million years ago (Mya), with a node age estimated at 40.63 Mya. These findings highlight that the genus Plasmodium, which includes species found in ungulates, birds, reptiles, and other mammals, does not form a monophyletic group. By incorporating Polychromophilus in bats and Plasmodium in ungulates, this study contributes significantly to understanding the phylogenetic relationships within the Haemosporida order. It provides valuable insights into the evolutionary history and interconnections among these diverse parasites, thereby expanding knowledge in this field.

Bartonella Infection in Fruit Bats and Bat Flies, Bangladesh

Bats harbor diverse intracellular Bartonella bacteria, but there is limited understanding of the factors that influence transmission over time. Investigation of Bartonella dynamics in bats could reveal general factors that control transmission of multiple bat-borne pathogens, including viruses. We used molecular methods to detect Bartonella DNA in paired bat (Pteropus medius) blood and bat flies in the family Nycteribiidae collected from a roost in Faridpur, Bangladesh between September 2020 and January 2021. We detected high prevalence of Bartonella DNA in bat blood (35/55, 64%) and bat flies (59/60, 98%), with sequences grouping into three phylogenetic clades. Prevalence in bat blood increased over the study period (33% to 90%), reflecting an influx of juvenile bats in the population and an increase in the prevalence of bat flies. Discordance between infection status and the clade/genotype of detected Bartonella was also observed in pairs of bats and their flies, providing evidence that bat flies take blood meals from multiple bat hosts. This evidence of bat fly transfer between hosts and the changes in Bartonella prevalence during a period of increasing nycteribiid density support the role of bat flies as vectors of bartonellae. The study provides novel information on comparative prevalence and genetic diversity of Bartonella in pteropodid bats and their ectoparasites, as well as demographic factors that affect Bartonella transmission and potentially other bat-borne pathogens.

Detection of bacterial and protozoan pathogens in individual bats and their ectoparasites using high-throughput microfluidic real-time PCR

Among the most studied mammals in terms of their role in the spread of various pathogens with possible zoonotic effects are bats. These are animals with a very complex lifestyle, diet, and behavior. They are able to fly long distances, thus maintaining and spreading the pathogens they may be carrying. These pathogens also include vector-borne parasites and bacteria that can be spread by ectoparasites such as ticks and bat flies. In the present study, high-throughput screening was performed and we detected three bacterial pathogens: Bartonella spp., Neoehrlichia mikurensis and Mycoplasma spp., and a protozoan parasite: Theileria spp. in paired samples from bats (blood and ectoparasites). In the samples from the bat-arthropod pairs, we were able to detect Bartonella spp. and Mycoplasma spp. which also showed a high phylogenetic diversity, demonstrating the importance of these mammals and the arthropods associated with them in maintaining the spread of pathogens. Previous studies have also reported the presence of these pathogens, with one exception, Neoehrlichia mikurensis, for which phylogenetic analysis revealed less genetic divergence. High-throughput screening can detect more bacteria and parasites at once, reduce screening costs, and improve knowledge of bats as reservoirs of vector-borne pathogens. IMPORTANCE The increasing number of zoonotic pathogens is evident through extensive studies and expanded animal research. Bats, known for their role as reservoirs for various viruses, continue to be significant. However, new findings highlight the emergence of Bartonella spp., such as the human-infecting B. mayotimonensis from bats. Other pathogens like N. mikurensis, Mycoplasma spp., and Theileria spp. found in bat blood and ectoparasites raise concerns, as their impact remains uncertain. These discoveries underscore the urgency for heightened vigilance and proactive measures to understand and monitor zoonotic pathogens. By deepening our knowledge and collaboration, we can mitigate these risks, safeguarding human and animal well-being.

The diverse genetic genotypes of Bartonella species circulating in rodents from Inner Mongolia, Northern China

Bartonella are generally recognized as zoonotic pathogens of mammals, including many rodent species. However, data on the genetic diversity of Bartonella in some regions are still absent in China. In this study, we collected rodent samples (Meriones unguiculatus, Spermophilus dauricus, Eolagurus luteus, and Cricetulus barabensis) from Inner Mongolia located in Northern China. The Bartonella were detected and identified by sequencing the gltA, ftsZ, ITS, and groEL genes in them. An overall 47.27% (52/110) positive rate was observed. This may be the first report that M. unguiculatus and E. luteus harbor Bartonella. Phylogenetic and genetic analysis on gltA, ftsZ, ITS, and groEL genes indicated that the strains were divided into seven distinct clades, suggesting the diverse genetic genotypes of Bartonella species in this area. Of those, Clade 5 meets the criteria for identification as a novel species based on gene sequence dissimilarity to known Bartonella species and herein we name it "Candidatus Bartonella mongolica".

Molecular Detection and Phylogenetic Analyses of Diverse Bartonella Species in Bat Ectoparasites Collected from Yunnan Province, China

Bartonella species has been validated as blood-borne bacteria in mammals and has a substantial opportunity to be harbored by a variety of hematophagous arthropod vectors. Bats, along with their ectoparasites, are recognized worldwide as one of the natural reservoir hosts for these bacteria. However, there have been few investigations of Bartonella bacteria toward a broad range of obligated bat ectoparasites in China. Here, molecular detection of Bartonella species was performed to survey the infection among bat ectoparasites and follow-up phylogenetic analyses to further characterize the evolutionary relationships of the genus. A total of 434 bat ectoparasites involving four types of arthropods, namely, bat mites, bat tick, bat fleas, and bat flies (further divided into traditionally fly-like bat flies and wingless bat flies) were collected in 10 trapping sites in Yunnan Province, southwestern China. Bartonella was detected by PCR amplification and sequencing through four gene target fragments (gltA, ftsZ, rpoB, and ITS). Accordingly, diverse Bartonella species were discovered, including both the validated species and the novel genotypes, which were characterized into several geographical regions with high prevalence. Phylogenetic analyses based on gltA and multi-locus concatenated sequences both demonstrated strong phylogeny-trait associations of Bartonella species from bats and their parasitic arthropods, suggesting the occurrence of host switches and emphasizing the potential connecting vector role of these ectoparasites. Nevertheless, the maintenance and transmission of Bartonella in both bat and hemoparasite populations have not been fully understood, as well as the risk of spillage to humans, which warrants in-depth experimental studies focusing on these mammals and their ectoparasites.