Emerging risks at the vampire bat–prion interface: implications for wildlife, livestock, and public health

Abstract

The role of the Common Vampire Bat (Desmodus rotundus) as a vector for chronic wasting disease (CWD) remains uninvestigated, and the effects of prion exposure in vampire bats are unknown. Desmodus feeds on the blood of various animals including deer, livestock, and humans across its expansive distribution. Given the continued southward spread of CWD in North American cervid populations and potential for the disease to already be circulating in Mexico, where it may overlap with established Desmodus populations, it is critical to assess potential risks at the interface between vampire bats and prion-infected hosts. Desmodus is also predicted to expand its range northward, potentially establishing populations in CWD-endemic regions of the southern United States, further underscoring the need for proactive surveillance and research on the ecological and epidemiological implications of this emerging interface. We explore aspects of prion biology and the natural history of Desmodus, highlighting factors that may contribute to prion exposure events among vampire bats and sympatric mammals. In light of Desmodus feeding behaviors, vampire bats could experience elevated prion exposures over time if they encounter CWD-positive prey. We recommend risk assessments and surveillance to evaluate vampire bat–prion transmission pathways that could impact mammalian wildlife, livestock, and human health.

Chronic wasting disease (CWD), a fatal prion disease of cervids, is rapidly expanding across North America and may already be circulating in northern Mexico. Vampire bats are predicted to overlap with CWD-positive deer populations; thus, their feeding behavior raises the possibility of prion exposure and novel prion transmission pathways. This emerging interface underscores the need for targeted surveillance and risk assessment to evaluate potential impacts on wildlife, livestock, and public health.

Globally, there are only 3 species of obligate blood-feeding mammals: the White-winged Vampire Bat (Diaemus youngi), Hairy-legged Vampire Bat (Diphylla ecaudata), and Common Vampire Bat (Desmodus rotundus; Wilson and Reeder 2005). All are found in the Neotropics; however, of the 3 species, D. rotundus is the most widespread and regionally abundant. The Common Vampire Bat inhabits both arid and humid regions of the Neotropics, ranging from Mexico throughout Central and South America, including some islands of the southern Caribbean, and extending as far south as Argentina and Chile (Greenhall et al. 1983). Desmodus feeds on the blood of various prey species including wild animals (e.g., mammals, birds, reptiles, and amphibians), livestock, poultry, and humans (Brown and Escobar 2023) with a preference for large-bodied, easily accessible prey such as cattle. Desmodus is a well-known reservoir for pathogens of concern, particularly rabies, and several countries have implemented population control efforts (e.g., culling) with varying success to mitigate the risk of associated disease outbreaks in livestock and humans (Calisher et al. 2006; Streicker et al. 2012).

Currently, the northernmost distribution of Desmodus is in northern Mexico (Wilson and Mittermeier 2019), although several demographic models predict a climate-driven expansion of the species into the southern United States within the next 10 to 50 yr (Mistry and Moreno-Valdez 2009; Hayes and Piaggio 2018; Fig. 1). Numerous studies have examined the host and vector status of Desmodus for viral and bacterial pathogens, and preliminary efforts are underway to predict and plan for its potential emergence as a rabies vector in the United States (Constantine 1988; Bodenchuk and Bergman 2020). However, the potential for Desmodus populations to acquire or transmit infectious proteins (i.e., prions) remains unexplored. Given the ongoing spread of chronic wasting disease (CWD) in North America and the possibility that CWD-positive cervids have already been imported into Mexico, the presence of prions in blood raises ­important questions about previously unconsidered transmission routes via vampire bat feeding.

Prion transmission, strain adaptation, and cross-species dynamics

Prion diseases are invariably fatal neurodegenerative disorders of mammals caused by misfolded prion proteins (PrP^Sc). Unlike disease-causing bacteria or viruses, infectious prions lack genetic material and propagate by inducing normal prion proteins (PrP^C) in the host to misfold (Prusiner 1982). Importantly, all mammals express PrP^C and exhibit varying degrees of susceptibility to prion diseases (Eraña et al. 2024). The self-templating properties of PrP^Sc result in the formation of prion fibrils that spread through the host, colonizing nervous tissues including the brain, where they cause progressive vacuolar degeneration and amyloid plaque formation, ultimately leading to the death of the host. Prions can be transmitted to a susceptible individual directly through exposure to body fluids and tissues (e.g., brain, saliva, blood, urine, feces, etc.), and indirectly through the environment (e.g., soil, plants; Miller et al. 2004; Mathiason et al. 2006; Safar et al. 2008; Pritzkow et al. 2015). Regarding bodily fluids, PrP^Sc circulates in the blood of infected individuals (animal or human), as documented by a combination of blood transfusion-associated infections, bioassays, and protein-seeded amplification diagnostics (Castilla et al. 2005; Mathiason et al. 2010; Thomas et al. 2023). The blood of an infected individual can also harbor infectious prions not only once clinical signs appear but throughout the characteristically long incubation period of prion diseases, which can span years (Chen et al. 2010; Thomas et al. 2024).

Interspecies transmission of prion diseases has been documented both in nature and experimentally. For example, the bovine spongiform encephalopathy (BSE) outbreak during the 1980’s and 1990’s demonstrated interspecies transmission between cattle and a variety of other mammals including humans, leading to over 300 confirmed or probable human deaths (Wells et al. 1987; Leggett et al. 1990; Kirkwood and Cunningham 1994; Hill et al. 1997; Bons et al. 1999; Collee et al. 2006). From a broader perspective, interspecies PrP^Sc transmission events have been documented across multiple prion diseases including scrapie, transmissible mink encephalopathy, CWD, and others (Bartz et al. 2000; Sigurdson 2008; Bian et al. 2017). Despite these observations, significant species barriers exist across mammals, and these barriers (e.g., genotype, protein structure, cellular environment) can prevent the direct spread of prions (Wells 2003; Race et al. 2018; Perrin-Stowe et al. 2022; Groveman et al. 2024).

Similar to viral and bacterial infections, distinct prion strains influence key features of disease including incubation period, clinical signs, tissue tropism, and host range (Bartz 2016). Strain-specific conformations of PrP^Sc are hypothesized to underlie prion adaptation to new host species (Bessen and Marsh 1994). Just as multiple or dual viral strains can infect a single host, multiple prion strains can circulate within an infected individual, and these strains have the potential to differentially overcome species barriers, causing disease in some host species while remaining non-pathogenic in others (Steadman et al. 2024). Although a single individual can produce multiple strains, species-level differences in PrP^C conformation play a role in whether interspecies transmission is possible (Block and Bartz 2023). Recent data indicate that the passage of CWD prions through mammalian scavengers can alter prion pathogenesis and species barriers through the modification of prion protein structures (Bartz et al. 1998; Moore et al. 2017). Moreover, a growing body of evidence indicates that particular non-cervid mammalian lineages (e.g., rodents of the genera Castor, Peromyscus, and Microtus) are susceptible to CWD prions (Heisey et al. 2010; Herbst et al. 2022; Myskiw et al. 2025). Several distinct CWD PrP^Sc strains are known to circulate throughout North America; however, the potential for uncharacterized strains with unknown capacities to cross species barriers raises significant concerns (Raymond et al. 2007; Angers et al. 2010; Otero et al. 2023; Bartz et al. 2024).

CWD in North American cervids is notable for producing relatively high levels of PrP^Sc in peripheral tissues, excreta, and especially blood (Mathiason et al. 2006; Henderson et al. 2015). Species such as White-tailed Deer, Mule Deer, and Elk are highly susceptible to CWD. Experimental challenge studies, based on White-tailed Deer, have shown that as little as 100 to 300 nanograms of CWD-positive brain inoculum can transmit the disease (Denkers et al. 2020). Of note, CWD-positive individuals harbor infectious prion levels in their blood that are sufficient to transmit the disease to other cervids (Mathiason et al. 2010). Recent research has shown that Ixodes spp. ticks engorged on CWD-positive blood can harbor up to 42 infectious doses of CWD (Inzalaco et al. 2023), based on estimates from Denkers et al. (2020) for White-tailed Deer. Given these observations, an important question arises: What are the implications when an obligate blood-feeding mammal routinely feeds on CWD-positive cervids?

The vampire bat–prion interface

Over the past twenty years, CWD has spread across the United States and Canada, with a growing number of positive cervids documented in New Mexico and Texas (National Wildlife Health Center 2025). The ranges of CWD-susceptible cervids, including White-tailed Deer (Odocoileus virginianus) and Mule Deer (O. hemionus), extend southward into Mexico, where they overlap with the ranges of other potentially susceptible cervids. Notably, the range of O. virginianus extends throughout Central America and northern South America (Wilson and Mittermeier 2019). Because of this connectivity, it is likely that CWD will continue spreading southward, affecting deer populations throughout Mexico and eventually Central America and South America. Although CWD has not been detected in Mexico as of this writing, 2 key observations suggest that the disease has great potential to already be circulating in Mexican cervids. First, CWD is circulating in wild Mule Deer and White-tailed Deer populations in New Mexico and Texas counties along the Mexican border, with prevalence rates as high as 11% in Mule Deer herds within the Hueco Mountains (National Wildlife Health Center 2025). Second, Texas Parks and Wildlife Department records show that from 2021 to 2025, hundreds of live White-tailed Deer were shipped to Mexico from Texas ranches that were later confirmed to have CWD-positive deer on their property (Texas Parks and Wildlife Dept., H. Reed pers. comm., 5 May 2025). For these reasons, the geographic distribution of Desmodus in Mexico should be regarded as an area of heightened risk for ongoing interactions between vampire bats and CWD-positive cervids (Fig. 1).

Fig. 1.

Map of the southern United States and Mexico showing the approximate distribution of chronic wasting disease (CWD) in wild and captive cervids (circles) and the approximate distribution of the common vampire bat (Desmodus rotundus) in Mexico (shading), both as of 2025. Given recent shipments of live White-tailed Deer from Texas facilities that are now CWD positive to Mexico (Texas Parks and Wildlife), CWD is likely already circulating in Mexican cervids. For this reason, the entire distribution of Desmodus represents an area of enhanced risk (shading). Desmodus is predicted to colonize the southern United States in the coming decades, and CWD has steadily spread southward in the United States (gradient inlay). Thus, a contact zone between vampire bats and known CWD-positive cervid herds is predicted (line). Created with BioRender.com.

The northernmost range of Desmodus is just south of the Mexico–US border, and these bat populations are documented to feed on cervids (Sánchez-Cordero et al. 2011; Brown and Escobar 2023). The expansion of CWD across the southern United States toward northern Mexico is occurring concurrently with a northern expansion of Desmodus, and recent predictions indicate that Desmodus will extend its distribution into Texas, New Mexico, and Arizona over the coming decades (Van de Vuurst et al. 2024; Van de Vuurst et al. 2025). Because deer are a prey species of vampire bats throughout their Neotropical distribution, Desmodus will likely encounter CWD-positive cervids in both Mexico and, eventually, the southern United States (Fig. 1). Knowing this, several important questions arise when examining the vampire bat–prion interface. Are vampire bats susceptible to particular strains of CWD prions? Can Desmodus serve as a vector of infectious CWD prions to cervids or other susceptible prey species, such as cattle, sheep, and pigs (Hamir et al. 2006, 2007; Moore et al. 2017)? Are CWD prion strain characteristics altered after passage through vampire bats and, if so, what species are susceptible to vampire bat-passed prions?

Desmodus behavioral ecology and prion ­transmission risks

Understanding the natural history and key behaviors of D. rotundus, as well as the behavioral impacts of prion disease on CWD-infected prey is essential for assessing the potential risks associated with the vampire bat–prion interface. For example, individual vampire bats often select and repeatedly feed on specific prey individuals (Goodwin and Greenhall 1961; Gröger and Wiegrebe 2006). When the movement of these prey animals is restricted (i.e., being held in livestock pens), the likelihood increases that a particular bat from a nearby roost will return to the same prey individual night after night (Moya et al. 2015). Importantly, captive cervid herds used for hunting, venison production, or other byproducts (e.g., antler velvet) are relatively common in southern Texas and Mexico (Adams et al. 2016; Bringans 2022). Much like captive herds of cattle or pigs, farmed cervids provide the ideal prey situation for Desmodus because they often prefer to feed on ­populations that are easy to locate (Greenhall 1972).

The optimal foraging strategy of vampire bats increases the likelihood of encounters with CWD prions, as Desmodus would be expected to preferentially feed within herds of CWD-positive deer over time. Deer in the clinical stages of CWD exhibit cognitive impairment, abnormal behavior, and reduced mobility, potentially making them more accessible to vampire bats. In the absence of effective control measures over time, CWD prevalence can exceed 45% in wild deer herds and 80% in captive herds (reviewed in National Academies of Sciences, Engineering, and Medicine 2024). A single D. rotundus blood meal can contain approximately 20 ml blood and could harbor numerous infectious doses of CWD prions, as suggested by ID50 estimates from blood-engorged ticks (Inzalaco et al. 2023), based on White tailed Deer estimates from Denkers et al. (2020). These dynamics raise serious concerns about the potential role of vampire bats in prion transmission, particularly given their frequent feeding on livestock, which could act as intermediaries in the introduction of prions into both animal and human food systems. Addressing and mitigating these risks will be essential for protecting food security and preventing broader prion transmission scenarios (Fig. 2).

Fig. 2.

Schematic highlighting potential prion (PrP^Sc) transmission or exposure pathways associated with Desmodus rotundus feeding on Chronic Wasting Disease-positive cervids. Infectious prions are known to circulate within the blood of CWD-positive cervids; thus, vampire bats feeding on positive cervids would be exposed to prions. Risks associated Desmodus rotundus exposure to PrP^Sc are unknown and require additional research across multiple areas. Created with BioRender.com.

Following a feeding event, vampire bats typically return to a roost, which—depending on local ecological conditions—can house tens to thousands of densely clustered individuals (Greenhall et al. 1983). These densely organized roosts create the opportunity for another vampire bat behavior with significant implications for prion transmission networks: blood-meal sharing. Upon returning to the roost, a bat that has successfully acquired a blood meal may regurgitate and share it with a neighboring bat or offspring that did not acquire a blood meal (Wilkinson 1984). From a prion perspective, this behavior would effectively spread prion-infected blood meals to other bats, potentially amplifying CWD-prion exposure events across entire Desmodus colonies. Repeated nightly feeding on CWD-positive deer could therefore create an environment that sustains exposure to prions, both for individual vampire bats and entire colonies (Fig. 2). Although empirical data are lacking, the potential for vampire bats to act as prion vectors across a range of prey species, or to develop vampire bat-specific prion disease after repeated exposure events to CWD, represent critical and unexplored risk pathways.

Vampire bat roost ecology and the potential for environmental prion accumulation

Understanding how CWD prions might persist and spread through the environment following consumption by Desmodus is critical for assessing broader risks of environmental contamination. CWD prions are resistant to degradation in the environment and are documented to remain infectious within a given environment for years, with no defined upper limit (Miller et al. 2004; Saunders et al. 2008; David Walter et al. 2011; Li et al. 2025). Desmodus is known to occupy roosts in a wide variety of natural and anthropogenic structures, ranging from tree hollows and caves to abandoned buildings and water wells (Greenhall et al. 1983). Vampire bat guano often accumulates in thick layers or piles on roost floors. If prions pass into guano, then these fecal accumulations could serve as an indefinite source of prion exposure to animals and humans exposed to the roost environment. Moreover, bat guano is commonly used as a fertilizer in agriculture, and given that CWD prions can be absorbed by and remain infectious within plant tissues (Pritzkow et al. 2015), this raises concerns about multiple environmental exposure pathways (Fig. 2).

Several studies have shown that the passage of CWD prions through species such as raccoons, mice, and mountain lions can alter prion excretion loads and/or pathogenesis, either enhancing or diminishing risks to various hosts (Baune et al. 2021; Cassmann et al. 2022; Myskiw et al. 2025). It is plausible that the passage of CWD prions through Desmodus could lead to the emergence of prion strains with unknown species barriers and transmissibility. However, this possibility might require replication of infectious prions within vampire bats. Furthermore, the roosting sites of Desmodus colonies that feed on CWD-positive cervid populations may serve as reservoirs for prion accumulation over time (Fig. 2). If CWD prions remain intact and infectious after passing the gastrointestinal tract of Desmodus, then the concentration of prions in Desmodus guano deposits will present an unquantified risk for prion disease transmission to a variety of mammals. Alternatively, it is equally plausible that unique features of the Desmodus digestive system, shaped by the evolution of its sanguivorous diet such as its specialized protein-processing enzymes and gut microbiome (Zepeda Mendoza et al. 2018) may effectively diminish or neutralize the infectivity of ingested CWD prions.

Plausible scenario and risk assessment need

Based on the discussion above, a plausible scenario emerges in Mexico and the southern United States, where CWD-positive cervid herds, both wild and captive, are expected to overlap with D. rotundus (Fig. 1). In these areas, vampire bats may feed on CWD-positive deer herds. The late-stage neurological symptoms of individual infected deer make them more vulnerable to predation. Furthermore, the presence of captive deer breeding and hunting facilities across the southern United States and Mexico increases the likelihood of predation. The feeding behaviors of Desmodus, coupled with blood-meal sharing, could lead to elevated bat-to-bat prion exposure events and the concentration of prions with undetermined zoonotic transmission potential in guano deposits at roosting sites. Considering the wide range of species preyed upon by Desmodus and the variety of organisms that inhabit or interact with roosting sites (including at least 45 other bat species known to co-roost with Desmodus; Greenhall et al. 1983), the likelihood of both direct and indirect multi-species exposure to CWD prions passed through bats is significant. These dynamics raise the possibility that vampire bats could serve not only as passive carriers but also as active vectors, transmitting CWD prions between infected and naïve deer and potentially other susceptible species.

CWD has not been documented to pass from cervids to humans; however, the risk of transmission is non-zero (Osterholm et al. 2019; Hannaoui et al. 2022; Bartz et al. 2024). Increased human exposure to CWD prions provides an opportunity for strain adaptations that could cross the species barrier. With respect to livestock, CWD prions have been shown experimentally to cause prion disease in cattle, sheep, and pigs through both intracranial and oral-nasal routes of exposure; therefore, Desmodus-mediated transmission of CWD prions to these species is a food security concern (Hamir et al. 2007; Moore et al. 2017). We do not fully understand all the factors influencing species barriers for prion transmission, but given the 100% fatality rate of prion diseases and potential for multi-species prion transmission, investigating the vampire bat-prion-livestock network is justified. From an economic perspective, several studies have examined the negative economic impacts that vampire bats have on livestock and healthcare sectors across South and North America, losses estimated in the millions of US dollars (Meltzer and Rupprecht 1998; Anderson et al. 2014a, 2014b; Bodenchuk and Bergman 2020). These estimates, however, are based primarily on rabies outbreaks, a disease for which vaccines and management strategies exist. Should a Desmodus-mediated prion transmission pathway emerge—exposing wildlife, livestock, and potentially humans to prions—the economic repercussions would far exceed those linked to rabies. For instance, the US Food and Drug Administration has estimated that a BSE outbreak in the United States could result in at least $15 billion in lost sales revenue, with an additional $12 billion in carcass disposal costs (Pritchett et al. 2005). At minimum, Desmodus-related prion exposure events to sheep, goats, cattle, and humans would trigger costly and prolonged monitoring programs for scrapie, BSE, and variant Creutzfeldt-Jakob disease, alongside potential disruptions to domestic and international trade in meat, dairy, and animal by-products.

If prions were to persist within vampire bat populations, the likelihood of prion disease spillover to D. rotundus, other wild mammals, livestock, or humans through feeding events is increased. These observations, combined with environmental prion accumulation of strains with unknown species barriers in roost sites, amplify the urgency of addressing this risk. We strongly recommend risk assessments to evaluate the potential for vampire bats to serve as reservoirs and/or vectors of infectious prions. These assessments should include ecological studies, prion transmission experiments, and surveillance in regions where Desmodus and CWD-positive cervids are likely to overlap. Addressing this emerging issue proactively will be essential to mitigate future risks to wildlife and livestock health, related economies, and public health.

Author contributions

Lexi E. Frank (Visualization, Writing—original draft, Writing—review & editing), Jason C. Bartz (Conceptualization, Writing—original draft, Writing—review & editing), and Peter A. Larsen (Conceptualization, Funding acquisition, Writing—original draft, Writing—review & editing)

Funding

This research was funded in part by the Minnesota Environment and Natural Resource Trust Fund as recommended by the Legislative-Citizen Commission on Minnesota Resources.

Conflict of interest

Peter A. Larsen is a co-founder and stock owner of Priogen Corp, a diagnostic company specializing in the ultra-sensitive detection of pathogenic proteins associated with prion and protein-misfolding diseases. The University of Minnesota licensed patent applications to Priogen Corp. These interests have been reviewed and managed by the University of Minnesota in accordance with its conflict of interest policies.