From dogs to bats: Concerns regarding vampire bat-borne rabies in Brazil

Rabies transmitted from vampires to cattle: An overview

Rabies is a zoonotic infectious disease of global distribution that impacts human and animal health. In rural Latin America, rabies negatively impacts food security and the economy due to losses in livestock production. The common vampire bat, Desmodus rotundus, is the main reservoir and transmitter of rabies virus (RABV) to domestic animals in Latin America. Desmodus rotundus RABV is known to impact the cattle industry, from small farmers to large corporations. We assessed the main patterns of rabies in cattle attributed to D. rotundus RABV across Latin America. Epidemiological data on rabies from Latin America were collected from the Pan American Health Organization spanning the 1970-2023 period. Analyses revealed an average of 450 outbreaks annually for the countries where D. rotundus is distributed, with at least 6 animals dying in each outbreak. Brazil, Colombia, Peru, and Mexico were the Latin American countries with the highest number of rabies outbreaks during the study period and are the most affected countries in recent years. Findings suggest a re-emergence of bat-borne rabies in the region with more outbreaks reported in recent years, especially during the 2003-2020 period. Rabies outbreaks in cattle in the 2000-2020 period were significantly more frequent than in previous decades, with an increase in cross-species transmission after 2002. The size of outbreaks, however, was smaller in recent years, involving lower cattle mortality. Peru, El Salvador, and Brazil showed a strong association (R = 0.73, p = 0.01) between rabies incidence in D. rotundus (rates per million humans: 1.61, 0.94, and 1.09, respectively) and rabies outbreaks in cattle (rates per million cattle: 465.85, 351.01, and 48.22, respectively). A sustained, standardized, and widespread monitoring of D. rotundus demography and health could serve to inform an early warning system for the early detection of RABV and other bat-borne pathogens in Latin America. Current data can be used to forecast when, where, and in which intensity RABV outbreaks are more likely to occur in subtropical and tropical Latin America. A decrease in the size of outbreaks could suggest that strategies for epidemic management (e.g., education, early diagnosis, vaccination) have been effective. The increase in the number of outbreaks could suggest that the factors facilitating cross-species transmission could be on the rise.

Elfadl A, Kodama C, Zughaier SM, Farag E, Bansal D. Epidemiology, transmission dynamics, risk factors, and future directions of rabies in the Arabian Peninsula using one health approach: a review

Despite global initiatives to eliminate dog-mediated human rabies by 2030, the Arabian Peninsula faces challenges due to insufficient data. This review addresses the current rabies situation and knowledge gaps in the region and proposes One Health interventions. Employing a mixed-method approach combining scoping and systematic review, the study commenced with a Delphi discussion to identify knowledge gaps and set objectives. The literature search encompassed published articles and grey literature. The spatial and temporal distribution of rabies was analysed, alongside quantitative meta-analyses to assess prevalence. Rabies virus gene sequences from the NCBI database were examined for reservoir hosts and evolutionary patterns. The final Delphi discussion with experts focused on addressing knowledge gaps and formulating One Health interventions. The first reported human rabies case in this region occurred in Saudi Arabia in 1980. Yemen reported the highest number of cases (439), followed by Iraq (249), Saudi Arabia (91), Jordan (14), and Oman (9). Fox bites accounted for the most cases (47.4%), followed by dog (36.8%) and wild animal (15.8%) bites. The virus was detected in at least 21 animal species. Phylogenetic analysis detected a single strain with two clades, with foxes being the primary virus reservoir. However, the experts expressed scepticism about the accuracy of rabies reports in scientific literature. To achieve the 2030 goal of eliminating dog-mediated human rabies, a stepwise approach towards rabies elimination assessment is crucial in the region. Enhanced surveillance, awareness campaigns, and access to post exposure prophylaxis are essential to address the disease burden.

The Silent Threat: Unraveling the Impact of Rabies in Herbivores in Brazil

Rabies, a zoonotic viral disease, poses a significant threat due to its adaptability to diverse environments. Herbivore rabies, predominantly affecting cattle, horses, and goats in Brazil, remains a concern, results in substantial losses in the livestock industry, and poses risks to public health. Rabies virus transmission, primarily through hematophagous bats in Latin America, underscores the need for effective strategies, and vaccination plays a crucial role in controlling herbivorous rabies, with systematic vaccination beingly the primary method. Efforts to control rabies in herbivores include vaccination campaigns, public awareness programs, and the enhancement of surveillance systems. Despite these initiatives, rabies persists and imposes an economic burden and a significant health risk. Economic impacts include losses in the livestock industry, trade restrictions on livestock products, and financial burdens on governments and farmers owing to control measures. Despite the considerable costs of campaigns, surveillance, and control, investing in rabies vaccination and control not only safeguards livestock, but also preserves public health, reduces human cases, and strengthens the sustainability of the livestock industry. Mitigating the impact of herbivorous rabies in Brazil requires integrated approaches and continuous investments in vaccination, surveillance, and control measures to protect public health and ensure the sustainability of the livestock industry, thus contributing to food and economic security.

Spatial clusters, temporal behavior, and risk factors analysis of rabies in livestock in Ecuador

Rabies, a globally distributed and highly lethal zoonotic neglected tropical disease, has a significant impact in South America. In Ecuador, animal rabies cases are primarily linked to livestock, and hematophagous bats play a crucial role in disease transmission. This study aims to identify temporal trends, spatial patterns, and risk factors for animal rabies in Ecuador between 2014 and 2019. Epidemiological survey reports from the official Animal Rabies Surveillance Program of the Phyto and Zoosanitary Regulation and Control Agency of Ecuador (AGROCALIDAD) were used. The Animal Rabies Surveillance Program from AGROCALIDAD consists of an official passive surveillance program that receives reports from farmers or individuals (both trained or untrained) who have observed animals with neurological clinical signs and lesions compatible with bat bites, or who have seen or captured bats on their farms or houses. Once this report is made, AGROCALIDAD personnel is sent for field inspection, having to confirm the suspicion of rabies based on farm conditions and compatibility of signs. AGROCALIDAD personnel collect samples from all suspicious animals, which are further processed and analyzed using the Direct Fluorescent Antibody (DFA) test for rabies confirmatory diagnosis. In this case, study data comprised 846 bovine farms (with intra-farm sample sizes ranging from 1 to 16 samples) located in different ecoregions of Ecuador; out of these, 397 (46.93%) farms tested positive for animal rabies, revealing six statistically significant spatial clusters. Among these clusters, three high-risk areas were identified in the southeast of Ecuador. Seasonality was confirmed by the Ljung-Box test for both the number of cases (p < 0.001) and the positivity rate (p < 0.001). The Pacific Coastal lowlands and Sierra regions showed a lower risk of positivity compared to Amazonia (OR = 0.529; 95% CI = 0.318 - 0.883; p = 0.015 and OR = 0.633; 95% CI = 0.410 - 0.977; p = 0.039, respectively). The breeding of non-bovine animal species demonstrated a lower risk of positivity to animal rabies when compared to bovine (OR = 0.145; 95% CI = 0.062 - 0.339; p < 0.001). Similarly, older animals exhibited a lower risk (OR = 0.974; 95% CI = 0.967 - 0.981; p < 0.001). Rainfall during the rainy season was also found to decrease the risk of positivity to animal rabies (OR = 0.996; 95% CI = 0.995 - 0.998; p < 0.001). This study underscores the significance of strengthening the national surveillance program for the prevention and control of animal rabies in Ecuador and other countries facing similar epidemiological, social, and geographical circumstances.

Rabies Virus-Neutralizing Antibodies in Free-Ranging Invasive Wild Boars (Sus scrofa) from Brazil

Rabies, one of the most lethal global zoonoses, affects all mammals. It remains circulating worldwide in sylvatic cycles through terrestrial and airborne reservoirs, and in Brazil, bats are currently the main reservoirs and source of transmission. Wild boars, an important invasive alien species in Brazil, are a proven food source for hematophagous bats and may participate in the Brazilian sylvatic cycle of rabies. We evaluated the presence of this pathogen in hunted wild boars from the São Paulo state using histopathology, the direct fluorescent antibody test (DFA), viral isolation in cell culture (VICC), the rapid fluorescent focus inhibition test (RFFIT), and quantitative reverse transcription polymerase chain reaction (RT-qPCR). The results of histopathological, DFA, VICC, and RT-qPCR analysis were negative for all samples; seven serum samples tested positive in the RFFIT, and titers ranged from 0.13 IU/mL to 0.5 IU/mL. The presence of rabies virus-neutralizing antibodies in the studied wild boars suggests the circulation of the virus in these animals. Educative actions directed at hunters should include information on the prevention of this important zoonosis.

Gut microbial shifts in vampire bats linked to immunity due to changed diet in human disturbed landscapes

Anthropogenic land-use change alters wildlife habitats and modifies species composition, diversity, and contacts among wildlife, livestock, and humans. Such human-modified ecosystems have been associated with emerging infectious diseases, threatening human and animal health. However, human disturbance also creates new resources that some species can exploit. Common vampire bats (Desmodus rotundus) in Latin America constitute an important example, as their adaptation to human-modified habitats and livestock blood-feeding has implications for e.g., rabies transmission. Despite the well-known links between habitat degradation and disease emergence, few studies have explored how human-induced disturbance influences wildlife behavioural ecology and health, which can alter disease dynamics. To evaluate links among habitat disturbance, diet shifts, gut microbiota, and immunity, we quantified disturbance around roosting caves of common vampire bats in Costa Rica, measured their long-term diet preferences (livestock or wildlife blood) using stable isotopes of carbon and nitrogen, evaluated innate and adaptive immune markers, and characterized their gut microbiota. We observed that bats from roosting caves with more cattle farming nearby fed more on cattle blood. Moreover, gut microbial richness and the abundance of specific gut microbes differed according to feeding preferences. Interestingly, bats feeding primarily on wildlife blood harboured a higher abundance of the bacteria Edwardsiella sp., which tended to be associated with higher immunoglobulin G levels. Our results highlight how human land-use change may indirectly affect wildlife health and emerging infectious diseases through diet-induced shifts in microbiota, with implications for host immunity and potential consequences for susceptibility to pathogens.

The impact of anthropogenic climate change on pediatric viral diseases

The adverse effects of climate change on human health are unfolding in real time. Environmental fragmentation is amplifying spillover of viruses from wildlife to humans. Increasing temperatures are expanding mosquito and tick habitats, introducing vector-borne viruses into immunologically susceptible populations. More frequent flooding is spreading water-borne viral pathogens, while prolonged droughts reduce regional capacity to prevent and respond to disease outbreaks with adequate water, sanitation, and hygiene resources. Worsening air quality and altered transmission seasons due to an increasingly volatile climate may exacerbate the impacts of respiratory viruses. Furthermore, both extreme weather events and long-term climate variation are causing the destruction of health systems and large-scale migrations, reshaping health care delivery in the face of an evolving global burden of viral disease. Because of their immunological immaturity, differences in physiology (e.g., size), dependence on caregivers, and behavioral traits, children are particularly vulnerable to climate change. This investigation into the unique pediatric viral threats posed by an increasingly inhospitable world elucidates potential avenues of targeted programming and uncovers future research questions to effect equitable, actionable change. IMPACT: A review of the effects of climate change on viral threats to pediatric health, including zoonotic, vector-borne, water-borne, and respiratory viruses, as well as distal threats related to climate-induced migration and health systems. A unique focus on viruses offers a more in-depth look at the effect of climate change on vector competence, viral particle survival, co-morbidities, and host behavior. An examination of children as a particularly vulnerable population provokes programming tailored to their unique set of vulnerabilities and encourages reflection on equitable climate adaptation frameworks.

Epidemiology and Control of Rabies in Cattle and Equines in Rondônia State, a Brazilian's Legal Amazon Area

Rabies is a fatal neglected tropical zoonosis, and its significance for domestic herbivores in the rural cycle is probably associated with rainforest deforestation, livestock, and agricultural expansion. This epidemiological survey aimed to study the occurrence of rabies in bovines and equines in the state of Rondônia, located in the Brazilian's Legal Amazon, between the years 2002 and 2021, correlating these findings with the prophylactic strategies adopted by the local sanitary agency for rabies control. During this period, 201 cases were observed in bovines and 23 in equines. A downward trend in rabies incidence was observed for both domestic herbivores. Rabies did not show a higher occurrence in any specific time of the year, and epidemic periods varied during some years for bovines and equines. Using the Generalized estimating equations (GEE) method, a multiple model approach was obtained with the explanatory variables significantly associated with the decrease in rabies incidence in cattle and horses during the study period: the ratio of treated bats and ratio of vaccine doses sold. Furthermore, the ratio of printed educative material was positively associated with rabies incidence. Despite a decreasing trend in rabies occurrences in this Amazon rainforest area, likely due to the actions taken by the animal sanitary agency, rabies remains endemic and requires monitoring, as well as prophylactic strategies to control this disease.

Rabies virus variants from bats closely related to variants found in marmosets (Callithrix jacchus), a neglected source of human rabies infection in Brazil

Rabies is a fatal viral zoonosis caused by rabies virus (RABV). RABV infects the central nervous system and triggers acute encephalomyelitis in both humans and animals. Endemic in the Brazilian Northeast region, RABV emergence in distinct wildlife species has been identified as a source of human rabies infection and as such, constitutes a public health concern. Here, we performed post-mortem RABV analyses of 144 encephalic tissues from bats sampled from January to July 2022, belonging to 15 different species. We identified phylogenetically distinct RABV from Phyllostomidae and Molossidae bats circulating in Northeastern Brazil. Phylogenetic clustering revealed the close evolutionary relationship between RABV viruses circulating in bats and variants hosted in white-tufted marmosets, commonly captured to be kept as pets and linked to human rabies cases and deaths in Brazil. Our findings underline the urgent need to implement a phylogenetic-scale epidemiological surveillance platform to track multiple RABV variants which may pose a threat to both humans and animals.

A review of the diet of the common vampire bat (Desmodus rotundus) in the context of anthropogenic change

The common vampire bat (Desmodus rotundus) maintains a diverse, sanguivorous diet, utilizing a broad range of prey taxa. As anthropogenic change alters the distribution of this species, shifts in predator-prey interactions are expected. Understanding prey richness and patterns of prey selection is, thus, increasingly informative from ecological, epidemiological, and economic perspectives. We reviewed D. rotundus diet and assessed the geographical, taxonomical, and behavioral features to find 63 vertebrate species within 21 orders and 45 families constitute prey, including suitable host species in regions of invasion outside D. rotundus' range. Rodentia contained the largest number of species utilized by D. rotundus, though cattle were the most commonly reported prey source, likely linked to the high availability of livestock and visibility of bite wounds compared to wildlife. Additionally, there was tendency to predate upon species with diurnal activity and social behavior, potentially facilitating convenient and nocturnal predation. Our review highlights the dietary heterogeneity of D. rotundus across its distribution. We define D. rotundus as a generalist predator, or parasite, depending on the ecological definition of its symbiont roles in an ecosystem (i.e., lethal vs. non-lethal blood consumption). In view of the eminent role of D. rotundus in rabies virus transmission and its range expansion, an understanding of its ecology would benefit public health, wildlife management, and agriculture.

Supplementary Information

The online version contains supplementary material available at 10.1007/s42991-023-00358-3.

The Virome of Bats Inhabiting Brazilian Biomes: Knowledge Gaps and Biases towards Zoonotic Viruses

Bats host a large variety of viruses, including some that may infect other vertebrates and humans. Research on bat-borne viruses attracted significant attention in recent years mainly due to epizootics caused by viruses having bats as hosts. The characterization of the viral communities of bats was then prioritized, but despite increasing efforts, there are large disparities in the geographical ranges covered and the methodologies employed around the world. As a result, large gaps remain in our current understanding of bat viromes and their role in disease emergence. This is particularly true for megadiverse regions in Latin America. This review aims to summarize the current understanding about bat viruses that inhabit Brazilian biomes, one of the most bat species-rich and diverse regions of the globe. Taking into account all known bat-associated viral families studied in Brazilian biomes, we found that almost half of all bat species (86/181 species) were not investigated for viruses at all. Moreover, only a small fraction of viral lineages or families have been studied more in depth, usually employing targeted methods with limited power to characterize a broad virus diversity. Additionally, these studies relied on limited spatiotemporal sampling and small sample sizes. Therefore, our current understanding of bat viral communities in the Brazilian biomes is limited and biased at different levels, limiting zoonotic risk assessments of bat-borne viruses. Considering these limitations, we propose strategies to bridge the existing gaps in the near future. IMPORTANCE Bat-borne viruses have attracted much attention due to zoonotic outbreaks with large consequences to humans. Because of that, virus characterization in bats has been prioritized in tropical regions of the globe. However, bat-virus research in Latin America and particularly in Brazil, which are among the most bat species-rich regions of the world, are highly biased toward zoonotic viruses and known bat reservoir species. These results have direct implication for virus studies in general but also for new zoonotic virus and spillover events characterization. The limited knowledge we currently have about the virome of Brazilian bats drastically limits any broad assessment of zoonotic viruses they carry and calls for coordinated and large-scale studies to fill this crucial knowledge gap.