Biology subjects

Dyer, K. E.

Publications and source records attributed to Dyer, K. E..

6 recordsLinked to original sources

bioRxiv2026

Validating wing biopsies for blood-borne pathogen characterization in bats

Wildlife surveillance is critical for tracking disease emergence, characterizing pathogen diversity, and assessing spillover risks. Blood-borne pathogens are of particular interest for such efforts due to their global distribution, broad host taxa, and zoonotic potential. Despite the need to monitor blood-borne pathogens, blood collection efforts are costly for both biologists and the wildlife being sampled (i.e., time-consuming and stressful), hindering our ability to expand and enhance surveillance efforts. There is thus a pressing need for reliable methods for detecting blood-borne pathogens that minimize sampling efforts and wildlife stress. Vascular tissues can contain enough blood to detect infections while minimizing sampling effort and stress on wildlife, but it is unclear how pathogen detection and characterization from these tissues compared to blood. To evaluate the reliability of using vascular tissues for detecting blood-borne pathogens in wildlife, we collected paired samples of blood and wing biopsies from individual common vampire bats (Desmodus rotundus) and molecularly screened them for bartonellae, hemotropic mycoplasmas (hemoplasmas), and trypanosomes. The probability of detection was consistently lower in wing tissues than in blood for all pathogens, possibly due to blood vessel avoidance when collecting the former. However, we detected infection in wing tissues of at least two individual bats for each blood-borne pathogen. Paired-positive individuals mostly showed high sequence concordance between tissues, indicating frequent detection of the same infections. Estimated sample sizes needed to detect a single infection and the reported prevalences were similar (i.e., n = 10-39). Due to the lower probability of infection in wing tissues compared to blood, we suggest that using these samples to estimate infection prevalence of blood-borne pathogens is not ideal. However, our results demonstrate that vascular tissues are viable for initial pathogen assessment and discovery to help target surveillance efforts in the future.

ecology↗

bioRxiv2025

Vampire bats in Belize harbor multiple Trypanosoma cruzi genotypes: implications for parasite transmission at the wildlife-domestic-human interface

BackgroundChagas disease, caused by Trypanosoma cruzi, is a neglected tropical disease with complex sylvatic and domestic transmission cycles involving vectors, mammalian hosts, and humans. The common vampire bat (Desmodus rotundus) is an obligate blood-feeding species that frequently interacts with livestock and humans, yet their role in parasite maintenance in Central America remains poorly characterized. Methodology/Principal FindingsWe analyzed 205 blood samples from vampire bats collected at two sites in northern Belize over three years (2019, 2021, 2022). PCR screening revealed an overall T. cruzi prevalence of 41.5% and increasing infection risks over time. The amplicon-based next-generation sequencing of the parasite mini-exon locus identified 36 unique haplotypes belonging to five DTUs: TcI, TcIV, TcV, TcVI, and TcBat. TcBat was present in half of the samples sequenced. TcBat and TcVI, were detected in Belize for the first time. Belizean TcBat haplotypes clustered closely with Colombian reference sequences, and a subset formed a Belize-specific clade, indicating previously unrecognized TcBat diversity in the region; in contrast, Brazilian TcBat sequences were more distantly related. Conclusions/SignificanceVampire bats in Belize harbor diverse T. cruzi genotypes, including DTUs with established roles in human disease. Given their obligate blood diet, frequent feeding on livestock, and occasional biting of humans, vampire bats may serve as bridge hosts linking sylvatic, domestic, and human transmission cycles. Together with a recent report of an acute human Chagas disease case in northern Belize, these results underscore the need for integrated One Health surveillance of bats, vectors, livestock, and humans to better evaluate and mitigate the risk of Chagas disease in Central America. Author SummaryChagas disease, caused by the parasite Trypanosoma cruzi, is a major public health concern in the Americas but remains neglected in many regions, including Central America. The parasite is typically transmitted by kissing bugs, but wild mammals also serve as important hosts. Vampire bats (Desmodus rotundus) are unique because they feed exclusively blood and frequently bite livestock, and occasionally humans, creating opportunities for parasite transmission across different environments. In this study, we screened 205 vampire bats from northern Belize and found that over 40% were infected with T. cruzi. By sequencing parasite DNA, we discovered a surprising diversity of DTUs, including TcI, TcIV, TcV, TcVI, and TcBat. The detection of TcVI is particularly important, because this DTU, associated with human infections in South America, had not been previously reported in Belize. TcBat haplotypes were highly prevalent and genetically diverse. Our results show that vampire bats are important hosts of diverse T. cruzi genotypes in Belize and may act as bridge hosts between wildlife, livestock, human transmission cycles. Enhanced One Health surveillance across vectors, bats, domestic animals, and humans will be critical for understanding and preventing Chagas disease emergence in Central America.

molecular biology↗

bioRxiv2025

Neotropical bats as bioindicators for emerging zoonoses in Central America: A case study identifying Trypanosoma cruzi in bats from Belize using metagenomic next-generation sequencing

Emerging zoonoses remain a global public health concern. Surveillance of infectious and vector-borne diseases is vital for predicting and mitigating detrimental effects of zoonotic spillover events. Beyond assessing what microorganisms are circulating in specific environments, it is important to understand how potential reservoir hosts, especially animals such as bats, participate in pathogen transmission. Bats can host and potentially spread infections caused by bacteria, viruses, fungi, and protozoa. However, bats can also act as bioindicators that test positive for pathogenic microorganisms without necessarily contributing to the pathogen replication cycle. Metagenomic next-generation sequencing (mNGS) provides an efficient means to broadly screen for pathogens, although microorganism selectivity can sometimes be lower than targeted approaches. Pairing mNGS results with higher-sensitivity tests such as quantitative PCR (qPCR) can validate results and together these tools provide a relatively fast and reliable method for conducting surveillance. To test this approach, we surveyed the types of microorganisms circulating in Belize by collecting 263 blood samples from 20 different bat species captured in the Orange Walk District in 2019, 2022, and 2023. We used mNGS to initially characterize the microbial communities and qPCR to confirm presence and intensity of human pathogens of interest. We detected 1,430 different microorganisms with some relevance to human or animal health, including the protozoan Trypanosoma cruzi which was detected in the phyllostomid bats Desmodus rotundus and Artibeus jamaicensis. qPCR confirmed the presence and intensity of Trypanosoma cruzi in mNGS-positive bat samples. We documented the types of pathogenic microorganisms circulating throughout the bat community in northern Belize to demonstrate the capacity for bats to serve as bioindicators. Author SummaryTracking the spread of new and emerging zoonotic diseases is a major component of global health research. Pathogen surveillance is a vital part of predicting and reducing the consequences of disease outbreaks. Bats are a diverse group of mammals that can host and potentially transmit many pathogens that pose potential risks to human and environmental health. Our study surveyed blood samples (n=263) from 20 bat species collected from the Orange Walk District of Belize in 2019, 2022, and 2023. Metagenomic next-generation sequencing identified 1,430 different microorganisms that are considered potentially relevant to human or animal health. Among the microorganisms detected was Trypanosoma cruzi (T. cruzi), the protozoan causative agent of Chagas disease. T. cruzi was of particular interest due to its presence throughout the Americas and relevance to public health. We surveyed the types of microorganisms circulating throughout bat populations in northern Belize to demonstrate the ability of bats to act as bioindicators.

microbiology↗

bioRxiv2025

Longitudinal impacts of habitat fragmentation on Bartonella and hemotropic Mycoplasma dynamics in vampire bats

Habitat fragmentation can have negative impacts on wildlife including increased risk of infectious disease. To assess spatiotemporal changes in pathogen dynamics in vampire bats (Desmodus rotundus) in response to habitat fragmentation, we used general linear mixed models to investigate the influence of site, year, and tree cover on the prevalence of Bartonella and hemotropic Mycoplasma (hemoplasma) in bats in one large and one small forest fragment in northern Belize across seven years. Bartonella was marginally more prevalent in later years, while year and site differences in hemoplasma infections were driven by a peak in prevalence in the third year of the study in the small fragment. Bartonella prevalence increased with forest loss, but only in the large fragment, whereas hemoplasma prevalence showed a marginal negative response to forest loss. The effects of site, year, and forest loss on infection likelihood varied by pathogen genotype. Neither site nor year affected Bartonella genotypes, but one genotype was positively associated with tree cover. Two hemoplasma genotypes were influenced by year, but with differing trends. One genotype increased with tree cover regardless of site while another increased with forest loss at the small fragment only. Our work demonstrates that the effects of habitat fragmentation on infection prevalence depended on both the pathogen and specific genotype. Our findings complicate expectations of how habitat fragmentation affects infectious disease dynamics in bats. As such, management practices aimed at mitigating the impacts of infectious diseases in fragmented systems should be tailored to specific pathogens of concern.

ecology↗

bioRxiv2024

A paired analysis of mercury among non-invasive tissues to inform bat conservation monitoring

Contaminant exposure can harm wildlife. However, measuring contaminant exposure in wildlife can be challenging due to accessibility of species and/or sampling tissue matrices needed to answer research questions regarding exposure. For example, in bats and other taxa that roost, it may be best to collect pooled feces from colonies for minimal disturbance to species of conservation concern, but fecal contaminant concentrations do not provide contaminant bioaccumulation estimates. Thus, there is a need for quantifying relationships between sample matrices for measuring contaminant exposure to answer research questions pertaining to wildlife health and addressing conservation needs. Our goal was to determine relationships between fecal and fur total mercury (THg). To do so, we collected paired feces and fur from Mexican free-tailed bats (Tadarida brasiliensis) in summer 2023 in western Oklahoma at a maternity roost with no known Hg point source. We analyzed THg in each sample matrix for each individual (n = 48). We found no relationship between individual fecal and fur THg. However, when averaged, fur THg was 6.11 times greater than fecal THg. This factor can be used as a screening-level risk assessment of under-roost feces, which could then be followed by direct assessments of fur THg concentrations and health impacts. We encourage the use of this conversion factor across other insectivorous bat species and sites for estimating initial risks of contaminant exposure with minimal disturbance to species of conservation concern, when timely research for conservation actions are needed, and when a contaminant point source is not yet known. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=103 SRC="FIGDIR/small/587502v1_ufig1.gif" ALT="Figure 1"> View larger version (24K): org.highwire.dtl.DTLVardef@4bac41org.highwire.dtl.DTLVardef@1a13deorg.highwire.dtl.DTLVardef@e8e58org.highwire.dtl.DTLVardef@1a33a9d_HPS_FORMAT_FIGEXP M_FIG C_FIG Graphical abstract created in BioRender under a free subscription. Cave icon created by artist Freepik at https://www.flaticon.com/free-icons/cave. HighlightsO_LIUnder-roost sampling for contaminant exposure minimizes species disturbance C_LIO_LIContaminant exposure relationships in tissues can aide in measuring wildlife health C_LIO_LIWe sampled Tadarida brasilliensis for paired fecal and fur total Hg (THg) C_LIO_LITHg in fur averaged 6.11 times greater than feces C_LIO_LIThis factor can be used as an initial risk assessment for under-roost fecal sampling C_LIO_LIMore invasive follow-up sampling (bat fur) can be justified following risk assessment C_LI

ecology↗

bioRxiv2023

Bat cellular immunity varies by year and dietary habit in an increasingly fragmented landscape

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 animals physiological state, possibly resulting in immunosuppression and increased morbidity or mortality. We sought to determine how fragmentation 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 sanguinivory, frugivory, and insectivory respectively, in northern Belize. We compared estimated total white blood cell counts, leukocyte differentials, and infection status with two blood-borne bacterial pathogens (Bartonella spp. and hemoplasmas) of 118 bats captured in a broadleaf, secondary forest over a three-year period (2017-2019) of increasing habitat fragmentation. We found evidence for bat species-specific responses of cellular immunity between years, with neutrophil counts increasing in D. rotundus, but decreasing in S. parvidens and P. mesoamericanus from 2018 to 2019. However, the odds of infection with Bartonella spp. and hemoplasma spp. between 2017 and 2019 did not differ between bat species, contrary to our prediction that pathogen prevalence may increase with increased fragmentation. We conclude that each bat species invested differently in cellular immunity in ways that changed over years of increasing fragmentation. We recommend further research on the interactions between habitat fragmentation, cellular immunity, and infection across dietary habits of Neotropical bats for informed management and conservation.

ecology↗