Chagasian shortfall: a new concept on biodiversity and zoonoses knowledge gap

Chagasian shortfall: a new concept on biodiversity and zoonoses knowledge gap | Authorea try { document.documentElement.classList.add('js'); } catch (e) { } var _gaq = _gaq || []; _gaq.push(['_setAccount', 'G-8VDV14Y67G']); _gaq.push(['_trackPageview']); (function() { var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true; ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s); })(); Skip to main content Preprints Collections Wiley Open Research IET Open Research Ecological Society of Japan All Collections About About Authorea FAQs Contact Us Quick Search anywhere Search for preprint articles, keywords, etc. Search Search ADVANCED SEARCH SCROLL This is a preprint and has not been peer reviewed. Data may be preliminary. 21 January 2026 V1 Latest version Share on Chagasian shortfall: a new concept on biodiversity and zoonoses knowledge gap Authors : Roberto Leonan Novaes 0000-0003-1657-2807 [email protected] , Natasha Bertocchi , Carlos Grelle 0000-0002-8586-8655 , and Ricardo Moratelli Authors Info & Affiliations https://doi.org/10.22541/au.176900615.55250797/v1 204 views 76 downloads Contents Abstract Information & Authors Metrics & Citations View Options References Figures Tables Media Share Abstract The lack of knowledge of fundamental aspects of biodiversity is called shortfall, which has direct implications for scientific research, resource management, species conservation, and zoonotic disease surveillance. Seven proposed shortfalls pinpoint knowledge gaps for taxonomic diversity, geographic distribution, population dynamics, evolutionary relationships, abiotic tolerances, biotic interactions, and biological traits of species. However, there is a knowledge gap that has not been addressed among these shortfalls, which represents one of the most important pieces of biodiversity with implications for human well-being and species conservation: the zoonoses. We introduce here the concept of the Chagasian shortfall, which means that we do not know enough about pathogens, sylvatic reservoirs or hosts, vectors, and mainly epidemiological cycles, which makes it hard to understand how zoonotic diseases spread. This shortfall concept represents a new vision and the first step towards exploring knowledge limits of biodiversity, which is directly related to the One Health approach. Chagasian shortfall: a new concept on biodiversity and zoonoses knowledge gap Abstract The lack of knowledge of fundamental aspects of biodiversity is called shortfall, which has direct implications for scientific research, resource management, species conservation, and zoonotic disease surveillance. Seven proposed shortfalls pinpoint knowledge gaps for taxonomic diversity, geographic distribution, population dynamics, evolutionary relationships, abiotic tolerances, biotic interactions, and biological traits of species. However, there is a knowledge gap that has not been addressed among these shortfalls, which represents one of the most important pieces of biodiversity with implications for human well-being and species conservation: the zoonoses. We introduce here the concept of the Chagasian shortfall, which means that we do not know enough about pathogens, sylvatic reservoirs or hosts, vectors, and mainly epidemiological cycles, which makes it hard to understand how zoonotic diseases spread. This shortfall concept represents a new vision and the first step towards exploring knowledge limits of biodiversity, which is directly related to the One Health approach. Keywords Disease ecology, one health, pathogen-host association, zoonotic diseases. 1. The trouble of biodiversity knowledge lacks The lack of knowledge on fundamental aspects of the biology of species, including interactions among them, is called a shortfall, which has direct implications for scientific research, resource management, and biodiversity conservation (Baranzelli et al. 2023, Diniz-Filho et al. 2023). The shortfalls in biological knowledge need to be carefully identified and quantified, since biased and unrepresentative knowledge compromises the capacity to recognize and describe taxa, and their involvement in the ecological and evolutionary processes, preventing accurate predictions about how they might change in the future (Hortal et al. 2015). Thus, the existence of these shortfalls is a consequence of the gaps between realized and complete knowledge within a biological domain at the current time (Hortal et al. 2015). Seven proposed shortfalls pinpoint knowledge gaps for taxonomic diversity (Linnean), geographic distribution (Wallacean), abundance and populational dynamics (Prestonian), evolutionary relationships of taxa and their traits (Darwinian), abiotic tolerances (Hutchinsonian/Grinnellian), biotic interactions and functional diversity (Eltonian), and limited knowledge of species traits (Raunkiaeran) (Hortal et al. 2015, Rosado et al. 2016). However, there is a gap in knowledge that has not been addressed among these shortfalls, which represents one of the most important pieces of biological knowledge with implications for human well-being that is the epidemiological cycles that connect pathogens, reservoirs, hosts, and vectors in zoonotic diseases. Therefore, this is a shortfall that consider humans and, consequently, has a socio-ecological perspective. Consequently, human dimension needs to be into account as part of biological complexity in this new shortfall. 2. The pathogen-host conundrum Zoonoses are infectious diseases caused by pathogenic microorganisms (e.g. viruses) that have jumped from a non-human animal to humans, a phenomenon called spillover and it is a concern issue in public health (Ribeiro et al. 2021). From 60 to 75% of human emerging diseases are zoonoses, and approximately 220 viruses pathogenic to humans have been described (Anthony et al. 2013, Ellwanger and Chies 2021). However, there are estimates of over 320,000 viruses harboured by wild mammals throughout the world (Anthony et al. 2013). In other words, our current knowledge about the diversity of viruses — and consequently for reservoirs, hosts, and their zoonotic potential — is still crawling (Carlson et al. 2021, Lawrence et al. 2023). Furthermore, there is also a great diversity of bacteria, fungi, and protozoa potentially pathogenic to humans and other animals that remain completely unknown. The emergence of a zoonotic disease is due to a myriad of evolutionary, ecological, and social interspecific interactions, and their relationships with the environment (including humans and other animals) are quite complex (Ellwanger and Chies 2021, Stephens et al. 2021). For example, a single reservoir may harbor many pathogens that can be spilled over directly or indirectly to incidental new host species. Likewise, a single pathogen can have one or multiple reservoirs, hosts, and vectors. In fact, the relationship between pathogens, reservoirs/hosts, vectors, and habitats is not well known for most species and zoonotic diseases (Prince 1980, Ellwanger and Chies 2021, Guégan et al. 2024). For example, we can expect a spatial dynamic of diseases and we need into account the potential effect of vegetation cover on occurrence of a zoonosis (García-Peña et al. 2021, Roque et al. 2023, Mello et al. 2024). Many zoonoses do not have thei r epidemiological cycles described, and their natural reservoirs/hosts and vectors are unknown. In addition, knowledge about potentially new zoonotic microorganisms harboured by animals is also insufficient, although there are estimates for some taxa. A recent example illustrates the difficulty of understanding the epidemiology of infectious diseases emerged from the COVID-19 pandemic. The disease is caused by the betacoronavirus SARS-CoV-2 ( Betacoronavirus pandemicum ), first identified in humans (Zhou et al. 2020). Due to prior knowledge about other SARS-like viruses, it was speculated that bats could be their natural hosts (Zhou et al. 2020). Some hypotheses have been proposed connecting bats and pangolins based on coronaviruses phylogenetically close to SARS-CoV-2 (Lytras et al. 2021, Wacharapluesadee et al. 2021). However, even after a massive investigation, the origin of the virus and the disease are still unknown and epidemiological evolution of COVID-19 and the natural (or ancestral) host is uncertain (Lytras et al. 2021, Pekar et al. 2025). The truth is that even zoonoses discovered many decades ago, such as haemorrhagic fevers caused by the filoviruses, still do not have their epidemiological cycle completely known, and the natural hosts of Ebola, for example, have never been identified despite huge effort (Weber et al. 2023). On the other hand, some important zoonoses have been deeply investigated, and their wild circulation and transmission cycles are fully understood, such as Chagas and Nipah diseases (Singh et al. 2019, Lidani et al. 2019). However, even for zoonoses with well-established epidemiological cycles, the identification of novel hosts, reservoirs, and vectors remains a (virtual) possibility. Understanding the epidemiological cycle, including the identification of sylvatic reservoirs, intermediate hosts, vectors, and causes of spillover events, is a fundamental step towards establishing public policies to combat, mitigate, and mainly prevent outbreaks and epidemics of zoonotic diseases (Bell et al. 2025). The causes of spillover are hard to unravel, but searching for the influence of reservoir/host and vector abundance in synergy with habitat degradation can be an avenue for elucidating the epidemiological cycles (García-Peña et al. 2021, Roque et al. 2023, Mello et al. 2024). However, refined information on the geographic distribution, ecology, and natural history of animal reservoirs and hosts, in addition to data on the microorganisms hosted, is often required (Ellwanger and Chies 2021, Guégan et al. 2024, Bell et al. 2025). Therefore, the absence of this basic knowledge of biodiversity creates obstacles for scientific advances and, consequently, public health management. Therefore, clearly all these gaps — uncovered by Linnean, Wallacean, Eltonian, or other shortfalls — need a new concept that can summarize the knowledge bottlenecks, impacts on society, and ways to overcome them. 3. A new shortfall for biodiversity knowledge Here we introduce the concept of the Chagasian shortfall, which means that we do not know enough about pathogens, sylvatic reservoirs or hosts, vectors, and mainly epidemiological cycles, which makes it hard to understand how zoonotic diseases spread (Figure 1). The name was chosen honouring Carlos Chagas (1878–1934), a notable Brazilian scientist who dedicated his life to studying emerging infectious diseases. Carlos Chagas was the first and unique scientist in history to describe completely an infectious disease, including the pathogen ( Trypanosoma cruzi ), sylvatic reservoirs/hosts (opossums, armadillos, and other wild mammals), vectors (triatomine kissing bugs), clinical manifestations, and epidemiology, fulfilling Koch’s four postulates (Lidani et al. 2019). Therefore, the American trypanosomiasis, one of the zoonoses with the greatest impact on global public health, is popularly called Chagas disease. The emergence of a zoonotic disease often prompts critical questions aimed at understanding its epidemiological cycle (Figure 1), such as: (i) What (species) is the pathogen? (ii) What (species) is the sylvatic reservoir? (iii) Is transmission direct or are intermediate host (species) necessary to complete the cycle? (iv) What (species) is the vector? (v) Is there a possibility of human-to-human transmission? (vi) Are there adaptive mutations that could favour this type of transmission? Despite this, the truth is that most of these questions remain unanswered for the vast majority of zoonoses, even decades after their discovery. We know more about the few diseases that already have their hosts and vectors determined than we know about the hosts and vectors of most zoonotic diseases. Therefore, we define here the Chagasian shortfall as the lack of knowledge about the pathogens, sylvatic reservoir/hosts and vectors that make up the epidemiological cycle of zoonosis. Although the elements that compose the Chagasian shortfall are all recognized as aspects of biodiversity and its evolutionary and ecological interactions, they are frequently ignored by the scientific community comprised of systematists, evolutionary biologists, and ecologists. Showing the connection between the Chagasian shortfall and other biological knowledge gaps is important for creating a panoramic view that aims to integrate the different disciplines. Chagasian shortfall join elements of Linnean shortfall since the species must first be identified and named; Wallacean shortfall because the knowledge of geographic distribution of pathogens and hosts is needed; Eltonian shortfall because the species interactions are proxy for spillover; Prestonian shortfall since it is important know the species abundance and population fluctuation; and Darwinian shortfall because we need know the evolutionary (and co-evolutionary) relationships between taxa. All this knowledge is a tool for understanding the epidemiological cycle of zoonotic diseases, and the Chagasian shortfall has a purpose to unravel more complex interactions among species and achieve to identify epidemiological cycles — that is the true goal! On the other hand, the Chagasian shortfall differs from all other shortfalls in its conceptual attributes, although it may have common elements (Table 1). The Eltonian shortfall, for example, is related to scarcity of knowledge about intra- and interspecific interactions between pairs of species in a community and ecosystem ecology context (Hortal et al. 2015, Rosado et al. 2016), while the Chagasian shortfall refers to scarcity of knowledge about the obligatory or facultative interactions of species that compose an epidemiological cycle of a zoonotic disease, which encompasses intrinsic and extrinsic factors of these interactions. In the specific case of spillover of zoonotic pathogens, these interspecific interactions may not be natural or occur spontaneously in the habitats, but rather result from disruptive human actions, such as hunting and live animal trade (Magouras et al. 2020, Galindo-González 2022, Guégan et al. 2024). In this sense, these interactions are at many levels, including cellular and molecular, where the associations are mainly due to microbiological parasitic relationships. In other words, while the Eltonian shortfall focuses on interactions between pairs of organisms, the Chagasian shortfall aims to understand the consequences of these interactions from a more restrictive and disease-centered perspective with consequence to human health. Although some Eltonian interactions involve microorganisms and their hosts, not all such interactions lead to disease. Disease arises from physiological interactions between organisms, which depend on the immunological conditions under which these processes unfold. In this sense, the Chagasian shortfall is not concerned with interaction pairs per se, but rather with the ensemble of organisms, ecological and evolutionary processes, and immunological outcomes that collectively shape the conditions necessary for the emergence of zoonoses. Thus, the rational comprehension of phenomena and the study tools and methodologies are quite different among Chagasian, Eltonian and all other shortfalls, and we need new concepts to understand nature at different scales and contexts. The scarcity knowledge about the taxonomic identity, distribution, ecological interactions, population dynamics, and evolutionary relationships of organisms can make comprehension of the zoonoses epidemiology difficult. Thus, overcoming the Linnean, Wallacean, Eltonian, Prestonian, and Wallacean shortfalls can help reduce the Chagasian shortfall. 4. Next steps toward unfolding the epidemiological cycles of zoonoses Microorganisms that eventually cause disease in animals and humans are parts of biodiversity, but it has not been seen or studied in this way. With the low-cost development of Next-Generation Sequencing (NGS), we have begun to generate large volumes of data about pathogens present in the most varied species (e.g. whole viromes), but we still have limitations in extracting, processing, and understanding the biological implications available from the data (Mrozek et al. 2021). There is a lack of studies that seek to link pathogen discoveries at the molecular level with macroecological aspects of their reservoir/host animals, for example (Carlson et al. 2021). Furthermore, the interaction between pathogens and hosts is continuously under the influence of different evolutionary processes, such as mutation-selection-adaptation, as observed in “real-time” with the SARS-CoV-2 pandemic (Huang et al. 2021, Markov et al. 2023). This scenario requires an integrated vision of epidemiology with other branches of biological sciences (Guégan et al. 2024), which is in accordance with the One Health approach (Rabinowitz and Conti 2013). Therefore, the Chagasian shortfall sheds light on important aspects that must be addressed to generate the knowledge necessary to expand our capacity to understand the ecology of zoonoses and mitigate their impact. The proposal for this new shortfall concept also underscores the need to establish multidisciplinary research networks that integrate epidemiologists, microbiologists, ecologists, evolutionary biologists, and taxonomists, with the goal of combining complementary datasets to more effectively elucidate the epidemiological cycles of zoonoses. This approach will generate knowledge about the diversity, distribution, and interactions of taxa, thereby helping to reduce the Linnean, Wallacean, Darwinian, Eltonian, and all other shortfalls. It is possible that part of the data needed to fill the gaps hindering the understanding of the epidemiological cycles of some zoonoses is already available in taxonomic, ecological, and evolutionary studies, especially for diseases whose pathogens are associated with mammals and birds. However, there is a need to coordinate the integration of researchers with different expertise to direct analyses toward investigating the relationship between pathogen presence and patterns of ecological interaction, diversity, and distribution of hosts. Integrating these layers of information may help elucidate epidemiological cycles, thereby contributing significantly to public health policies. 5. Concluding remarks Considering the different microorganisms (many potentially pathogenic) ubiquitously present in the taxa, the Chagasian shortfall concept proposed here represents a new vision and the first step towards our knowledge of biodiversity and health relatedness. Furthermore, as previously described, interactions among humans, wild animals (reservoirs, host, and vectors), their pathogens and environments are a matter of public health policies of global interest. Moreover, we are continuously altering which potential pathogens, hosts, and vectors interact with one another as a result of our current lifestyle patterns, such as intra- and intercontinental human migrations, transport of animals and plants for food production, exotic species introduction, and habitat conversion by agrobusiness. So, the Chagasian shortfall is directly related to the One Health approach, and with potential to prevent the zoonotic outbreaks expected by climate and land use changes (Ribeiro et al. 2021, Guégan et al. 2024). 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Linnean Most of taxa have not been discovered or described Taxonomic diversity Wallacean Limits of geographic distribution knowledge of most taxa is scarce Geographic distribution Prestonian Populational data on taxa along space and time is incipient Populational dynamics Darwinian Lack of knowledge about the evolutionary relationships between taxa Taxa evolution Raunkiaeran Ecological function and functional traits of taxa are unknown Ecological function and functional traits Hutchinsonian Lack of knowledge about the responses and tolerances of taxa to abiotic conditions Abiotic tolerance Eltonian Lack of knowledge on interaction between taxa and their effects on individual survival and fitness Ecological interactions Chagasian Lack of knowledge about pathogens and their sylvatic reservoirs, hosts, and vectors Zoonosis epidemiological cycles Figure 1. Hypothetical epidemiological cycle for an emerging zoonotic disease, which may include sylvatic reservoirs (e.g., mammals or birds), intermediate hosts and/or vectors (e.g., arthropods) that can play a role in the spreading and interspecific transmission of pathogens, and humans (fundamental host for the definition of zoonosis). Although most human infectious diseases originate in wild animals, knowledge about the components that make up the epidemiological cycles of these zoonoses remains quite limited and many questions remain unanswered. The knowledge gap of the species involved in any of these stages of the epidemiological cycle characterizes the Chagasian shortfall. Information & Authors Information Version history V1 Version 1 21 January 2026 Copyright This work is licensed under a Non Exclusive No Reuse License. Keywords disease ecology one health pathogen-host association zoonotic diseases Authors Affiliations Roberto Leonan Novaes 0000-0003-1657-2807 [email protected] Fundação Oswaldo Cruz View all articles by this author Natasha Bertocchi Fundação Oswaldo Cruz View all articles by this author Carlos Grelle 0000-0002-8586-8655 Universidade Federal do Rio de Janeiro View all articles by this author Ricardo Moratelli Fundação Oswaldo Cruz View all articles by this author Metrics & Citations Metrics Article Usage 204 views 76 downloads .FvxKWukQNSOunydq8rnd { width: 100px; } Citations Download citation Roberto Leonan Novaes, Natasha Bertocchi, Carlos Grelle, et al. Chagasian shortfall: a new concept on biodiversity and zoonoses knowledge gap. Authorea . 21 January 2026. DOI: https://doi.org/10.22541/au.176900615.55250797/v1 If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. 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