Genetic diversity, infection prevalence, and possible transmission routes of Bartonella spp. in vampire bats

Zoonotic bacterial pathogens in bats samples around the world: a scoping review

The aim of this scoping review was to describe the zoonotic bacterial pathogens already reported and their frequency in different bat species. Six databases were searched, without restriction on the year or location where the studies were carried out. Based on the inclusion and exclusion criteria, 146 studies that were published between 1964 and 2020 (most after 2005) were selected. In these studies, 102 zoonotic bacterial genera were described in different samples of fourteen bat families in 55 countries, suggesting the possible role of bats as hosts for these pathogens. The pathogens mainly identified in bats were Bartonella spp., Leptospira spp. and Staphylococcus spp. In conclusion, the information provided by this scoping review expands the knowledge about zoonotic bacterial pathogens already identified in bats, which can guide epidemiological surveillance policies for these pathogens in different countries.

Geographically widespread and novel hemotropic mycoplasmas and bartonellae in Mexican free-tailed bats and sympatric North American bat species

Bacterial pathogens remain poorly characterized in bats, especially in North America. We describe novel (and in some cases panmictic) hemoplasmas (12.9% positivity) and bartonellae (16.7% positivity) across three colonies of Mexican free-tailed bats (Tadarida brasiliensis), a partially migratory species that can seasonally travel hundreds of kilometers. Molecular analyses identified three novel Candidatus hemoplasma species most similar to another novel Candidatus species in Neotropical molossid bats. We also detected novel hemoplasmas in sympatric cave myotis (Myotis velifer) and pallid bats (Antrozous pallidus), with sequences in the latter 96.5% related to C. Mycoplasma haemohominis. We identified eight Bartonella genotypes, including those in cave myotis, with 96.7% similarity to C. Bartonella mayotimonensis. We also detected Bartonella rochalimae in migratory Tadarida brasiliensis, representing the first report of this human pathogen in bats. The seasonality and diversity of these bacteria observed here suggest that additional longitudinal, genomic, and immunological studies in bats are warranted.

Bat cellular immunity varies by year and dietary habit amidst land conversion

Monitoring the health of wildlife populations is essential in the face of increased agricultural expansion and forest fragmentation. Loss of habitat and habitat degradation can negatively affect an animal's physiological state, possibly resulting in immunosuppression and increased morbidity or mortality. We sought to determine how land conversion may differentially impact cellular immunity and infection risk in Neotropical bats species regularly infected with bloodborne pathogens, and to evaluate how effects may vary over time and by dietary habit. We studied common vampire bats (Desmodus rotundus), northern yellow-shouldered bats (Sturnira parvidens) and Mesoamerican mustached bats (Pteronotus mesoamericanus), representing the dietary habits of sanguivory, frugivory and insectivory respectively, in northern Belize. We compared estimated total white blood cell count, leukocyte differentials, neutrophil to lymphocyte ratio and infection status with two bloodborne bacterial pathogens (Bartonella spp. and hemoplasmas) of 118 bats captured in a broadleaf, secondary forest over three years (2017-2019). During this period, tree cover decreased by 14.5% while rangeland expanded by 14.3%, indicating increasing habitat loss and fragmentation. We found evidence for bat species-specific responses of cellular immunity between years, with neutrophil counts significantly decreasing in S. parvidens from 2017 to 2018, but marginally increasing in D. rotundus. However, the odds of infection with Bartonella spp. and hemoplasmas between 2017 and 2019 did not differ between bat species, contrary to our prediction that pathogen prevalence may increase with land conversion. We conclude that each bat species invested differently in cellular immunity in ways that changed over years of increasing habitat loss and fragmentation. We recommend further research on the interactions between land conversion, immunity and infection across dietary habits of Neotropical bats for informed management and conservation.

Epidemiology of feline bartonellosis and molecular characteristics of Bartonella henselae in Bangladesh

Bartonellosis, a neglected vector-borne zoonotic disease transmitted from animals to humans, continues to threaten human and animal health significantly. This study aims to determine the epidemiology of feline bartonellosis and the molecular characteristics of Bartonella spp. in cats. From June 2018 to June 2020, 304 oral swabs were randomly collected from Bangladesh's Dhaka, Mymensingh, and Rajshahi districts. A pre-tested questionnaire was administered to collect data. Oral swabs were subjected to PCR targeting htrA gene to confirm Bartonella spp., which was subsequently validated through sequencing. Risk factors were identified using multivariable logistic regression analysis. The overall prevalence of feline bartonellosis was found to be 15.1 %. The following factors were significantly (p < 0.05) associated with Bartonella infection in risk factor analysis: cats aged ≥ 1 year (OR: 3.23, 95 % CI: 1.38-24.40), local breed cats (OR: 3.37, 95 % CI: 1.05-10.81), cats carrying fleas (OR: 2.33, 95 % CI: 1.93-13.45), antifleacidal drugs inconsistently administered cats (OR: 6.74, 95 % CI: 3.17-14.31), outdoor access cats (OR: 2.54, 95 % CI: 1.16-5.57). Notably, zoonotic B. henselae was confirmed through sequencing, establishing it as the causal agent of cat scratch disease. Phylogenetic analysis showed homology with B. henselae sequences from Brazil, Saint Kitts, and Nevis. We recommend consistent and appropriate flea control measures to curb its spread among Bangladeshi cats. Moreover, limiting outdoor exposure or implementing preventive measures for outdoor cats could reduce the disease burden. The associated human health risk can be decreased by effectively controlling this disease within the cat population.

Serum proteomics reveals a tolerant immune phenotype across multiple pathogen taxa in wild vampire bats

Bats carry many zoonotic pathogens without showing pronounced pathology, with a few exceptions. The underlying immune tolerance mechanisms in bats remain poorly understood, although information-rich omics tools hold promise for identifying a wide range of immune markers and their relationship with infection. To evaluate the generality of immune responses to infection, we assessed the differences and similarities in serum proteomes of wild vampire bats (Desmodus rotundus) across infection status with five taxonomically distinct pathogens: bacteria (Bartonella spp., hemoplasmas), protozoa (Trypanosoma cruzi), and DNA (herpesviruses) and RNA (alphacoronaviruses) viruses. From 19 bats sampled in 2019 in Belize, we evaluated the up- and downregulated immune responses of infected versus uninfected individuals for each pathogen. Using a high-quality genome annotation for vampire bats, we identified 586 serum proteins but found no evidence for differential abundance nor differences in composition between infected and uninfected bats. However, using receiver operating characteristic curves, we identified four to 48 candidate biomarkers of infection depending on the pathogen, including seven overlapping biomarkers (DSG2, PCBP1, MGAM, APOA4, DPEP1, GOT1, and IGFALS). Enrichment analysis of these proteins revealed that our viral pathogens, but not the bacteria or protozoa studied, were associated with upregulation of extracellular and cytoplasmatic secretory vesicles (indicative of viral replication) and downregulation of complement activation and coagulation cascades. Additionally, herpesvirus infection elicited a downregulation of leukocyte-mediated immunity and defense response but an upregulation of an inflammatory and humoral immune response. In contrast to our two viral infections, we found downregulation of lipid and cholesterol homeostasis and metabolism with Bartonella spp. infection, of platelet-dense and secretory granules with hemoplasma infection, and of blood coagulation pathways with T. cruzi infection. Despite the small sample size, our results suggest that vampire bats have a similar suite of immune mechanisms for viruses distinct from responses to the other pathogen taxa, and we identify potential biomarkers that can expand our understanding of pathogenesis of these infections in bats. By applying a proteomic approach to a multi-pathogen system in wild animals, our study provides a distinct framework that could be expanded across bat species to increase our understanding of how bats tolerate pathogens.

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.

Virulent Brucella nosferati infecting Desmodus rotundus has emerging potential due to the broad foraging range of its bat host for humans and wild and domestic animals

Desmodus rotundus, vampire bats, transmit dangerous infections, and brucellosis is a hazardous zoonotic disease, two adversities that coexist in the subtropical and tropical areas of the American continent. Here, we report a 47.89% Brucella infection prevalence in a colony of vampire bats inhabiting the tropical rainforest of Costa Rica. The bacterium induced placentitis and fetal death in bats. Wide-range phenotypic and genotypic characterization placed the Brucella organisms as a new pathogenic species named Brucella nosferati sp. nov., isolated from bat tissues, including the salivary glands, suggesting feeding behavior might favor transmission to their prey. Overall analyses placed B. nosferati as the etiological agent of a reported canine brucellosis case, demonstrating its potential for infecting other hosts. To assess the putative prey hosts, we analyzed the intestinal contents of 14 infected and 23 non-infected bats by proteomics. A total of 54,508 peptides sorted into 7,203 unique peptides corresponding to 1,521 proteins were identified. Twenty-three wildlife and domestic taxa, including humans, were foraged by B. nosferati-infected D. rotundus, suggesting contact of this bacterium with a broad range of hosts. Our approach is appropriate for detecting, in a single study, the prey preferences of vampire bats in a diverse area, demonstrating its suitability for control strategies where vampire bats thrive. IMPORTANCE The discovery that a high proportion of vampire bats in a tropical area is infected with pathogenic Brucella nosferati and that bats forage on humans and many wild and domestic animals is relevant from the perspective of emerging disease prevention. Indeed, bats harboring B. nosferati in their salivary glands may transmit this pathogenic bacterium to other hosts. This potential is not trivial since, besides the demonstrated pathogenicity, this bacterium possesses all the required virulent arsenal of dangerous Brucella organisms, including those that are zoonotic for humans. Our work has settled the basis for future surveillance actions in brucellosis control programs where these infected bats thrive. Moreover, our strategy to identify the foraging range of bats may be adapted for exploring the feeding habits of diverse animals, including arthropod vectors of infectious diseases, and therefore of interest to a broader audience besides experts on Brucella and bats.

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.

Characterizing the blood microbiota of omnivorous and frugivorous bats (Chiroptera: Phyllostomidae) in Casanare, eastern Colombia

Bats are known reservoirs of seemingly-innocuous pathogenic microorganisms (including viruses, bacteria, fungi, and protozoa), which are associated with triggering disease in other zoonotic groups. The taxonomic diversity of the bats' microbiome is likely associated with species-specific phenotypic, metabolic, and immunogenic capacities. To date, few studies have described the diversity of bat blood microbial communities. Then, this study used amplicon-based next generation sequencing of the V4 hypervariable region of the 16S-rRNA gene in blood samples from omnivorous (n = 16) and frugivorous (n = 9) bats from the department of Casanare in eastern Colombia. We found the blood microbiota in bats to be composed of, among others, Bartonella and Mycoplasma bacterial genera which are associated with various disease phenotypes in other mammals. Furthermore, our results suggest that the bats' dietary habits might determine the composition and the persistence of some pathogens over others in their bloodstream. This study is among the first to describe the blood microbiota in bats, to reflect on co-infection rates of multiple pathogens in the same individual, and to consider the influence of diet as a factor affecting the animal's endogenous microbial community.

Trends in Bacterial Pathogens of Bats: Global Distribution and Knowledge Gaps

Bats have received considerable recent attention for infectious disease research because of their potential to host and transmit viruses, including Ebola, Hendra, Nipah, and multiple coronaviruses. These pathogens are occasionally transmitted from bats to wildlife, livestock, and to humans, directly or through other bridging (intermediate) hosts. Due to their public health relevance, zoonotic viruses are a primary focus of research attention. In contrast, other emerging pathogens of bats, such as bacteria, are vastly understudied despite their ubiquity and diversity. Here, we describe the currently known host ranges and geographic distributional patterns of potentially zoonotic bacterial genera in bats, using published presence-absence data of pathogen occurrence. We identify apparent gaps in our understanding of the distribution of these pathogens on a global scale. The most frequently detected bacterial genera in bats are Bartonella, Leptospira, and Mycoplasma. However, a wide variety of other potentially zoonotic bacterial genera are also occasionally found in bats, such as Anaplasma, Brucella, Borrelia, Coxiella, Ehrlichia, Francisella, Neorickettsia, and Rickettsia. The bat families Phyllostomidae, Vespertilionidae, and Pteropodidae are most frequently reported as hosts of bacterial pathogens; however, the presence of at least one bacterial genus was confirmed in all 15 bat families tested. On a spatial scale, molecular diagnostics of samples from 58 countries and four overseas departments and island states (French Guiana, Mayotte, New Caledonia, and Réunion Island) reported testing for at least one bacterial pathogen in bats. We also identified geographical areas that have been mostly neglected during bacterial pathogen research in bats, such as the Afrotropical region and Southern Asia. Current knowledge on the distribution of potentially zoonotic bacterial genera in bats is strongly biased by research effort towards certain taxonomic groups and geographic regions. Identifying these biases can guide future surveillance efforts, contributing to a better understanding of the ecoepidemiology of zoonotic pathogens in bats.

The Amazonian Tropical Bites Research Initiative, a hope for resolving zoonotic neglected tropical diseases in the One Health era

BACKGROUND

Neglected tropical diseases (NTDs) disproportionately affect populations living in resource-limited settings. In the Amazon basin, substantial numbers of NTDs are zoonotic, transmitted by vertebrate (dogs, bats, snakes) and invertebrate species (sand flies and triatomine insects). However, no dedicated consortia exist to find commonalities in the risk factors for or mitigations against bite-associated NTDs such as rabies, snake envenoming, Chagas disease and leishmaniasis in the region. The rapid expansion of COVID-19 has further reduced resources for NTDs, exacerbated health inequality and reiterated the need to raise awareness of NTDs related to bites.

METHODS

The nine countries that make up the Amazon basin have been considered (Bolivia, Brazil, Colombia, Ecuador, French Guiana, Guyana, Peru, Surinam and Venezuela) in the formation of a new network.

RESULTS

The Amazonian Tropical Bites Research Initiative (ATBRI) has been created, with the aim of creating transdisciplinary solutions to the problem of animal bites leading to disease in Amazonian communities. The ATBRI seeks to unify the currently disjointed approach to the control of bite-related neglected zoonoses across Latin America.

CONCLUSIONS

The coordination of different sectors and inclusion of all stakeholders will advance this field and generate evidence for policy-making, promoting governance and linkage across a One Health arena.

Genomic Characterization of Three Novel Bartonella Strains in a Rodent and Two Bat Species from Mexico

Rodents and bats are the most diverse mammal group that host Bartonella species. In the Americas, they were described as harboring Bartonella species; however, they were mostly characterized to the genotypic level. We describe here Bartonella isolates obtained from blood samples of one rodent (Peromyscus yucatanicus from San José Pibtuch, Yucatan) and two bat species (Desmodus rotundus from Progreso, and Pteronotus parnellii from Chamela-Cuitzmala) from Mexico. We sequenced and described the genomic features of three Bartonella strains and performed phylogenomic and pangenome analyses to decipher their phylogenetic relationships. The mouse-associated genome was closely related to Bartonella vinsonii. The two bat-associated genomes clustered into a single distinct clade in between lineages 3 and 4, suggesting to be an ancestor of the rodent-associated Bartonella clade (lineage 4). These three genomes showed <95% OrthoANI values compared to any other Bartonella genome, and therefore should be considered as novel species. In addition, our analyses suggest that the B. vinsonii complex should be revised, and all B. vinsonii subspecies need to be renamed and considered as full species. The phylogenomic clustering of the bat-associated Bartonella strains and their virulence factor profile (lack of the Vbh/TraG conjugation system remains of the T4SS) suggest that it should be considered as a new lineage clade (L5) within the Bartonella genus.

Prevalence and Genetic Diversity of Bartonella Spp. in Northern Bats (Eptesicus nilssonii) and Their Blood-Sucking Ectoparasites in Hokkaido, Japan

We investigated the prevalence of Bartonella in 123 northern bats (Eptesicus nilssonii) and their ectoparasites from Hokkaido, Japan. A total of 174 bat fleas (Ischnopsyllus needhami) and two bat bugs (Cimex japonicus) were collected from the bats. Bartonella bacteria were isolated from 32 (26.0%) of 123 bats. Though Bartonella DNA was detected in 79 (45.4%) of the bat fleas, the bacterium was isolated from only one bat flea (0.6%). The gltA sequences of the isolates were categorized into genotypes I, II, and III, which were found in both bats and their fleas. The gltA sequences of genotypes I and II showed 97.6% similarity with Bartonella strains from a Finnish E. nilssonii and a bat flea from a E. serotinus in the Netherlands. The rpoB sequences of the genotypes showed 98.9% similarity with Bartonella strain 44722 from E. serotinus in Republic of Georgia. The gltA and rpoB sequences of genotype III showed 95.9% and 96.7% similarity with Bartonella strains detected in shrews in Kenya and France, respectively. Phylogenetic analysis revealed that Bartonella isolates of genotypes I and II clustered with Bartonella strains from Eptesicus bats in Republic of Georgia and Finland, Myotis bats in Romania and the UK, and a bat flea from an Eptesicus bat in Finland. In contrast, genotype III formed a clade with B. florencae, B. acomydis, and B. birtlesii. These data suggest that northern bats in Japan harbor two Bartonella species and the bat flea serves as a potential vector of Bartonella transmission among the bats.

A database of common vampire bat reports

The common vampire bat (Desmodus rotundus) is a sanguivorous (i.e., blood-eating) bat species distributed in the Americas from northern Mexico southwards to central Chile and Argentina. Desmodus rotundus is one of only three mammal species known to feed exclusively on blood, mainly from domestic mammals, although large wildlife and occasionally humans can also serve as a food source. Blood feeding makes D. rotundus an effective transmissor of pathogens to its prey. Consequently, this species is a common target of culling efforts by various individuals and organizations. Nevertheless, little is known about the historical distribution of D. rotundus. Detailed occurrence data are critical for the accurate assessment of past and current distributions of D. rotundus as part of ecological, biogeographical, and epidemiological research. This article presents a dataset of D. rotundus historical occurrence reports, including >39,000 locality reports across the Americas to facilitate the development of spatiotemporal studies of the species. Data are available at 10.6084/m9.figshare.15025296.

Measurement(s)	occurrence report
Technology Type(s)	digital curation
Sample Characteristic - Organism	Desmodus rotundus
Sample Characteristic - Location	North America • South America

Machine-accessible metadata file describing the reported data: 10.6084/m9.figshare.18745316

Molecular detection and genotype diversity of hemoplasmas in non-hematophagous bats and associated ectoparasites sampled in peri-urban areas from Brazil

Hemoplasmas have already been detected in bats in the United States of America, Spain, Australia, Chile, Brazil, Peru, Belize, Nigeria, Costa Rica, Germany, Switzerland and New Caledonia. The recent detection of hemoplasmas closely related to Mycoplasma haematohominis, an agent causing disease in humans, emphasizes the need for additional studies on the diversity of hemoplasmas in bats. The present work aimed to investigate the occurrence and assess the phylogenetic positioning and genetic diversity of hemoplasmas in bats and associated ectoparasites sampled in central-western Brazil. Overall, 43% (58/135) sampled bats and 1.56% (1/64) bat flies (Megistopoda aranea) were positive for hemoplasmas, however, twenty-four and two hemoplasma sequences were obtained from PCR assays targeting 16S and 23S rRNA genes, respectively, since the majority of the obtained amplicons showed faint bands in agarose gel electrophoresis. The obtained 16S rRNA sequences showed to be broadly distributed along the phylogenetic tree, albeit positioned within the 'Haemofelis group' and clustering with other bat-associated hemoplasmas. Twelve 16S rRNA hemoplasma genotypes were found among the 24 obtained sequences. When compared to other bat-related hemoplasmas sequences retrieved from the Genbank, 52 genotypes were found. The two 23S rRNA sequences obtained were positioned as a sister clade to "Candidatus Mycoplasma haematohydrochaerus", M. haemofelis and M. haemocanis. High genetic diversity was found among 16S rRNA hemoplasma sequences detected in non-hematophagous bats from central-western Brazil and previously detected in other regions of the world. Even though the genotype analysis showed that hemoplasmas from the same genus tend to group together, the results from the unipartite and bipartite analyses did not robustly support the hypothesis. Further studies addressing the specificity of hemoplasma genotypes according to bat species and genera should be performed.

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

The study of bacterial zoonoses has been under-pursued despite the fact that bacteria cause the majority of zoonotic diseases, of which 70% have a wildlife origin. More Bartonella species are being identified as the cause of human diseases, and several of them have been linked to domestic and wild animals. Bats are outstanding reservoirs for Bartonella species because of their wide distribution, mobility, roosting behaviour, and long life span. Here, we carried out a PCR-based survey on bats that were collected from 19 sampling sites in eight provinces of Thailand from February 2018 to April 2021. Bartonella infection was investigated in a total of 459 bats that belong to 24 different bat species (21 species of which had never been previously studied in Thailand). PCR diagnostics revealed that 115 out of 459 (25.5%) blood samples tested positive for Bartonella. The nucleotide identities of the Bartonella 16S rRNA sequences in this study were between 95.78-99.66% identical to those of known zoonotic species (Bartonella ancashensis, Bartonella henselae, Bartonella bacilliformis and Bartonella australis) as well as to an unidentified Bartonella spp. In addition, the citrate synthase (gltA) and RNA polymerase-beta subunit (rpoB) genes of Bartonella were sequenced and analyzed in positive samples. The gltA and rpoB gene sequences from Hipposideros gentilis and Rhinolophus coelophyllus bat samples showed low nucleotide identity (<95%) compared to those of the currently deposited sequences in the GenBank database, indicating the possibility of new Bartonella species. The phylogenetic inference and genetic diversity were generated and indicated a close relationship with other Bartonella species previously discovered in Asian bats. Overall, the current study demonstrates the primary evidence pointing to a potential novel Bartonella species in bats. This discovery also contributes to our current understanding of the geographical distribution, genetic diversity, and host ranges of bat-related Bartonella.

Bats and their ectoparasites (Nycteribiidae and Spinturnicidae) carry diverse novel Bartonella genotypes, China

Bartonella species are facultative intracellular bacteria and recognized worldwide as emerging zoonotic pathogens. Bartonella were isolated or identified by polymerase chain reaction (PCR) in bats and their ectoparasites worldwide, whereas the association between them was scarce, especially in Asia. In this study, a retrospective analysis with frozen samples was carried out to identify the genetic diversity of Bartonella in bats and their ectoparasites and to investigate the relationships of Bartonella carried by bats and their ectoparasites. Bats and their ectoparasites (bat flies and bat mites) were collected from caves in Hubei Province, Central China, from May 2018 to July 2020. Bartonella were screened by PCR amplification and sequencing of three genes (gltA, rpoB, and ftsZ). Bats, bat flies, and bat mites carried diverse novel Bartonella genotypes with a high prevalence. The sharing of some Bartonella genotypes between bats and bat flies or bat mites indicated a potential role of bat flies and bat mites as vectors of bartonellae, while the higher genetic diversity of Bartonella in bat flies than that in bats might be due to the vertical transmission of this bacterium in bat flies. Therefore, bat flies might also act as reservoirs of Bartonella. In addition, human‐pathogenic B. mayotimonesis was identified in both bats and their ectoparasites, which expanded our knowledge on the geographic distribution of this bacterium and suggested a potential bat origin with bat flies and bat mites playing important roles in the maintenance and transmission of Bartonella.

Disentangling interactions among mercury, immunity and infection in a Neotropical bat community

1. Contaminants such as mercury are pervasive and can have immunosuppressive effects on wildlife. Impaired immunity could be important for forecasting pathogen spillover, as many land-use changes that generate mercury contamination also bring wildlife into close contact with humans and domestic animals. However, the interactions among contaminants, immunity and infection are difficult to study in natural systems, and empirical tests of possible directional relationships remain rare. 2. We capitalized on extreme mercury variation in a diverse bat community in Belize to test association among contaminants, immunity and infection. By comparing a previous dataset of bats sampled in 2014 with new data from 2017, representing a period of rapid agricultural land conversion, we first confirmed bat species more reliant on aquatic prey had higher fur mercury. Bats in the agricultural habitat also had higher mercury in recent years. We then tested covariation between mercury and cellular immunity and determined if such relationships mediated associations between mercury and bacterial pathogens. As bat ecology can dictate exposure to mercury and pathogens, we also assessed species-specific patterns in mercury-infection relationships. 3. Across the bat community, individuals with higher mercury had fewer neutrophils but not lymphocytes, suggesting stronger associations with innate immunity. However, the odds of infection for haemoplasmas and Bartonella spp. were generally lowest in bats with high mercury, and relationships between mercury and immunity did not mediate infection patterns. Mercury also showed species- and clade-specific relationships with infection, being associated with especially low odds for haemoplasmas in Pteronotus mesoamericanus and Dermanura phaeotis. For Bartonella spp., mercury was associated with particularly low odds of infection in the genus Pteronotus but high odds in the subfamily Stenodermatinae. 4. Synthesis and application. Lower general infection risk in bats with high mercury despite weaker innate defense suggests contaminant-driven loss of pathogen habitat (i.e. anemia) or vector mortality as possible causes. Greater attention to these potential pathways could help disentangle relationships among contaminants, immunity and infection in anthropogenic habitats and help forecast disease risks. Our results also suggest that contaminants may increase infection risk in some taxa but not others, emphasizing the importance of considering surveillance and management at different phylogenetic scales.

Intra- and Inter-Host Assessment of Bartonella Diversity with Focus on Non-Hematophagous Bats and Associated Ectoparasites from Brazil

The relationship among bats, ectoparasites and associated microorganisms is important to investigate how humans can become exposed to zoonotic agents. Even though the diversity of Bartonella spp. in bats and ectoparasites has been previously reported, the occurrence of gltA genotypes within hosts has not been assessed so far. We aimed to investigate the genetic diversity of Bartonella spp. in non-hematophagous bats and associated ectoparasites by assessing cloned gltA Bartonella genotypes in intra- and inter-hosts levels, as well as by using three additional molecular markers. Overall, 13.5% (18/133) bat blood samples, 17.18% bat flies (11/64) and 23.8% (5/21) Macronyssidae mite pools showed to be positive for Bartonella spp. Seventeen positive samples were submitted to gltA-cloning and three clones were sequenced for each sample. We also obtained 11, seven and three sequences for nuoG, rpoB and ftsZ genes, respectively. None were positive for the other target genes. We found at least two genotypes among the three gltA-cloned sequences from each sample, and 13 between all the 51 sequences. Among the nuoG, rpoB and ftsZ sequences we found eight, five and three genotypes, respectively. In the phylogenetic analysis, the sequences were positioned mainly in groups related to Bartonella identified in rodents, bats and bat flies. Herein, we showed the genetic diversity of Bartonella in bat's blood and associated ectoparasites samples at both intra- and inter-host levels.

Molecular detection and genetic diversity of Bartonella species in large ruminants and associated ectoparasites from the Brazilian Cerrado

Currently, five Bartonella species and an expanding number of Candidatus Bartonella species have globally been reported in ruminants. Likewise, different Bartonella genotypes were identified. However, studies relating to ruminant-associated Bartonella in Brazil are scarce. The current study aimed to assess the prevalence and genetic diversity of Bartonella in cattle, buffaloes and associated ectoparasites in Brazil. For this purpose, EDTA-blood samples from 75 cattle and 101 buffaloes were sampled. Additionally, 128 Rhipicephalus microplus and one Amblyomma sculptum ticks collected from cattle, and 197 R. microplus, one A. sculptum and 170 lice (Haematopinus tuberculatus) collected from buffaloes were included. Bartonella DNA was initially screened through an HRM real-time PCR assay targeting the 16S-23S internal transcribed spacer (ITS), and the positive samples were submitted to an additional HRM assay targeting the ssrA gene. The HRM-positive amplicons were sequenced, and the nucleotide identity was assessed by BLASTn. Bartonella spp.-positive DNA samples were analysed by conventional PCR assays targeting the gltA and rpoB genes, and then, the samples were cloned. Finally, the phylogenetic positioning and the genetic diversity of clones were assessed. Overall, 21 of 75 (28%) cattle blood samples and 13 of 126 (10.3%) associated ticks were positive for Bartonella bovis. Out of 101 buffaloes, 95 lice and 188 tick DNA samples, one (1%) buffalo and four (4.2%) lice were positive for Bartonella spp. Conversely, none of the ticks obtained from buffaloes were positive for Bartonella. The Bartonella sequences from buffaloes showed identity ranging from 100% (ITS and gltA) to 94% (ssrA) with B. bovis. In contrast, the Bartonella DNA sequences from lice were identical (100%) to uncultured Bartonella sp. detected in cattle tail louse (Haematopinus quadripertusus) from Israel in all amplified genes. The present study demonstrates the prevalence of new B. bovis genotypes and a cattle lice-associated Bartonella species in large ruminants and their ectoparasites from Brazil. These findings shed light on the distribution and genetic diversity of ruminant- and ectoparasite-related Bartonella in Brazil.

Immune-challenged vampire bats produce fewer contact calls

Vocalizations are an important means to facilitate social interactions, but vocal communication may be affected by infections. While such effects have been shown for mate-attraction calls, other vocalizations that facilitate social contact have received less attention. When isolated, vampire bats produce contact calls that attract highly associated groupmates. Here, we test the effect of an immune challenge on contact calling rates of individually isolated vampire bats. Sickness behaviour did not appear to change call structure, but it decreased the number of contact calls produced. This effect could decrease contact with groupmates and augment other established mechanisms by which sickness reduces social encounters (e.g. mortality, lethargy and social withdrawal or disinterest).

Isolation and genetic properties of Bartonella in eastern bent-wing bats (Miniopterus fuliginosus) in Japan

The prevalence and genetic characteristics of Bartonella species in eastern bent-wing bats (Miniopterus fuliginosus) from Japan were investigated. Bartonella bacteria were isolated from 12/50 (24%) of bats examined. Analyses of sequence similarities of the citrate synthase gene (gltA) and RNA polymerase beta-subunit-encoding (rpoB) gene indicated that the isolates from M. fuliginosus were distinct from those present in known Bartonella species as the levels of similarity for both of the genes were lower than the cut-off values for species identification in Bartonella. A phylogenetic analysis of the gltA sequences revealed that the Miniopterus bat-associated strains fell into five genotypes (I to V). Though genotypes I to IV formed a clade with Bartonella from Miniopterus bats from Taiwan, genotype V made a monophyletic clade separate from other bat isolates. In a phylogenetic analysis with the concatenated sequences of the 16S rRNA, gltA, rpoB, cell division protein (ftsZ) gene, and riboflavin synthase gene (ribC), isolates belonging to genotypes I to IV clustered with Bartonella strains from Taiwanese Miniopterus bats, similar to the outcome of the phylogenetic analysis with gltA, whereas genotype V also made a monophyletic clade separate from other bat-associated Bartonella strains. The present study showed that M. fuliginosus in Japan harbor both genus Miniopterus-specific Bartonella suggesting to be specific to the bats in Japan.

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The prevalence of Bartonella in Miniopterus fuliginosus was 24%(12/50).

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M. fuliginosus in Japan harbored two novel Bartonella species in their blood.

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One Bartonella species was the genus Miniopterus-specific Bartonella.

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The other was distinct from other known bat-associated Bartonella.

Ecological and evolutionary drivers of haemoplasma infection and bacterial genotype sharing in a Neotropical bat community

Most emerging pathogens can infect multiple species, underlining the importance of understanding the ecological and evolutionary factors that allow some hosts to harbour greater infection prevalence and share pathogens with other species. However, our understanding of pathogen jumps is based primarily around viruses, despite bacteria accounting for the greatest proportion of zoonoses. Because bacterial pathogens in bats (order Chiroptera) can have conservation and human health consequences, studies that examine the ecological and evolutionary drivers of bacterial prevalence and barriers to pathogen sharing are crucially needed. Here were studied haemotropic Mycoplasma spp. (i.e., haemoplasmas) across a species-rich bat community in Belize over two years. Across 469 bats spanning 33 species, half of individuals and two-thirds of species were haemoplasma positive. Infection prevalence was higher for males and for species with larger body mass and colony sizes. Haemoplasmas displayed high genetic diversity (21 novel genotypes) and strong host specificity. Evolutionary patterns supported codivergence of bats and bacterial genotypes alongside phylogenetically constrained host shifts. Bat species centrality to the network of shared haemoplasma genotypes was phylogenetically clustered and unrelated to prevalence, further suggesting rare-but detectable-bacterial sharing between species. Our study highlights the importance of using fine phylogenetic scales when assessing host specificity and suggests phylogenetic similarity may play a key role in host shifts not only for viruses but also for bacteria. Such work more broadly contributes to increasing efforts to understand cross-species transmission and the epidemiological consequences of bacterial pathogens.

Leukocyte Profiles Reflect Geographic Range Limits in a Widespread Neotropical Bat

Quantifying how the environment shapes host immune defense is important for understanding which wild populations may be more susceptible or resistant to pathogens. Spatial variation in parasite risk, food and predator abundance, and abiotic conditions can each affect immunity, and these factors can also manifest at both local and biogeographic scales. Yet identifying predictors and the spatial scale of their effects is limited by the rarity of studies that measure immunity across many populations of broadly distributed species. We analyzed leukocyte profiles from 39 wild populations of the common vampire bat (Desmodus rotundus) across its wide geographic range throughout the Neotropics. White blood cell differentials varied spatially, with proportions of neutrophils and lymphocytes varying up to six-fold across sites. Leukocyte profiles were spatially autocorrelated at small and very large distances, suggesting that local environment and large-scale biogeographic factors influence cellular immunity. Generalized additive models showed that bat populations closer to the northern and southern limits of the species range had more neutrophils, monocytes, and basophils, but fewer lymphocytes and eosinophils, than bats sampled at the core of their distribution. Habitats with access to more livestock also showed similar patterns in leukocyte profiles, but large-scale patterns were partly confounded by time between capture and sampling across sites. Our findings suggest that populations at the edge of their range experience physiologically limiting conditions that predict higher chronic stress and greater investment in cellular innate immunity. High food abundance in livestock-dense habitats may exacerbate such conditions by increasing bat density or diet homogenization, although future spatially and temporally coordinated field studies with common protocols are needed to limit sampling artifacts. Systematically assessing immune function and response over space will elucidate how environmental conditions influence traits relevant to epidemiology and help predict disease risks with anthropogenic disturbance, land conversion, and climate change.

Percolation models of pathogen spillover

Predicting pathogen spillover requires counting spillover events and aligning such counts with process-related covariates for each spillover event. How can we connect our analysis of spillover counts to simple, mechanistic models of pathogens jumping from reservoir hosts to recipient hosts? We illustrate how the pathways to pathogen spillover can be represented as a directed graph connecting reservoir hosts and recipient hosts and the number of spillover events modelled as a percolation of infectious units along that graph. Percolation models of pathogen spillover formalize popular intuition and management concepts for pathogen spillover, such as the inextricably multilevel nature of cross-species transmission, the impact of covariance between processes such as pathogen shedding and human susceptibility on spillover risk, and the assumptions under which the effect of a management intervention targeting one process, such as persistence of vectors, will translate to an equal effect on the overall spillover risk. Percolation models also link statistical analysis of spillover event datasets with a mechanistic model of spillover. Linear models, one might construct for process-specific parameters, such as the log-rate of shedding from one of several alternative reservoirs, yield a nonlinear model of the log-rate of spillover. The resulting nonlinearity is approximately piecewise linear with major impacts on statistical inferences of the importance of process-specific covariates such as vector density. We recommend that statistical analysis of spillover datasets use piecewise linear models, such as generalized additive models, regression clustering or ensembles of linear models, to capture the piecewise linearity expected from percolation models. We discuss the implications of our findings for predictions of spillover risk beyond the range of observed covariates, a major challenge of forecasting spillover risk in the Anthropocene. This article is part of the theme issue 'Dynamic and integrative approaches to understanding pathogen spillover'.

Genetic diversity of Bartonella spp. in vampire bats from Brazil

Recently, an increasing number of Bartonella species have been emerged to cause human diseases. Among animal reservoirs for Bartonella spp., bats stand out due to their high mobility, wide distribution, social behaviour and long-life span. Although studies on the role of vampire bats in the epidemiology of rabies have been extensively investigated in Latin America, information on the circulation and genetic diversity of Bartonella species in these bat species is scarce. In the present work, 208 vampire bats, namely Desmodus rotundus (the common vampire bat; n = 167), Diphylla ecaudata (the hairy-legged vampire bat; n = 32) and Diaemus youngii (the white-winged vampire bat; n = 9) from 15 different states in Brazil were sampled. DNA was extracted from liver tissue samples and submitted to real-time PCR (qPCR) and conventional PCR (cPCR) assays for Bartonella spp. targeting five genetic loci, followed by phylogenetic and genotype network analyses. Fifty-one out of 208 liver samples (24.51%) were positive for Bartonella DNA in the ITS real-time PCR assay [40 (78.43%) of them were from D. rotundus from 11 states, and 11 (21.57%) samples from D. ecaudata from three states. Eleven genotypes were found for each gltA and rpoB genes. Several ITS sequences detected in the present study clustered within the lineage that includes B. bacilliformis and B. ancachensis. The Bayesian phylogenetic inference based on the gltA gene positioned the obtained sequences in six different clades, closely related to Bartonella genotypes previously detected in D. rotundus and associated ectoparasites sampled in Latin America. On the other hand, the Bartonella rpoB genotypes clustered together with the ruminant species, B. schoenbuchensis and B. chomelii. The present study describes for the first time the molecular detection of Bartonella spp. in D. ecaudata bats. It also indicates that Bartonella spp. of vampire bats are genetically diverse and geographically widespread in Brazil.

Habitat fragmentation is associated with dietary shifts and microbiota variability in common vampire bats

Host ecological factors and external environmental factors are known to influence the structure of gut microbial communities, but few studies have examined the impacts of environmental changes on microbiotas in free-ranging animals. Rapid land-use change has the potential to shift gut microbial communities in wildlife through exposure to novel bacteria and/or by changing the availability or quality of local food resources. The consequences of such changes to host health and fitness remain unknown and may have important implications for pathogen spillover between humans and wildlife. To better understand the consequences of land-use change on wildlife microbiotas, we analyzed long-term dietary trends, gut microbiota composition, and innate immune function in common vampire bats (Desmodus rotundus) in two nearby sites in Belize that vary in landscape structure. We found that vampire bats living in a small forest fragment had more homogenous diets indicative of feeding on livestock and shifts in microbiota heterogeneity, but not overall composition, compared to those living in an intact forest reserve. We also found that irrespective of sampling site, vampire bats which consumed relatively more livestock showed shifts in some core bacteria compared with vampire bats which consumed relatively less livestock. The relative abundance of some core microbiota members was associated with innate immune function, suggesting that future research should consider the role of the host microbiota in immune defense and its relationship to zoonotic infection dynamics. We suggest that subsequent homogenization of diet and habitat loss through livestock rearing in the Neotropics may lead to disruption to the microbiota that could have downstream impacts on host immunity and cross-species pathogen transmission.

Handling Stress and Sample Storage Are Associated with Weaker Complement-Mediated Bactericidal Ability in Birds but Not Bats

Variation in immune defense influences infectious disease dynamics within and among species. Understanding how variation in immunity drives pathogen transmission among species is especially important for animals that are reservoir hosts for zoonotic pathogens. Bats, in particular, have a propensity to host serious viral zoonoses without developing clinical disease themselves. The immunological adaptations that allow bats to host viruses without disease may be related to their adaptations for flight (e.g., in metabolism and mediation of oxidative stress). A number of analyses report greater richness of zoonotic pathogens in bats than in other taxa, such as birds (i.e., mostly volant vertebrates) and rodents (i.e., nonvolant small mammals), but immunological comparisons between bats and these other taxa are rare. To examine interspecific differences in bacterial killing ability (BKA), a functional measure of overall constitutive innate immunity, we use a phylogenetic meta-analysis to compare how BKA responds to the acute stress of capture and to storage time of frozen samples across the orders Aves and Chiroptera. After adjusting for host phylogeny, sample size, and total microbe colony-forming units, we find preliminary evidence that the constitutive innate immune defense of bats may be more resilient to handling stress and storage time than that of birds. This pattern was also similar when we analyzed the proportion of nonnegative and positive effect sizes per species, using phylogenetic comparative methods. We discuss potential physiological and evolutionary mechanisms by which complement proteins may differ between species orders and suggest future avenues for comparative field studies of immunity between sympatric bats, birds, and rodents in particular.