A One Medicine Mission for an Effective Rabies Therapy.

Despite the disease's long history, little progress has been made toward a treatment for rabies. The prognosis for patient recovery remains dire. For any prospect of survival, patients require aggressive critical care, which physicians in rabies endemic areas may be reluctant or unable to provide given the cost, clinical expertise required, and uncertain outcome. Systematic clinical research into combination therapies is further hampered by sporadic occurrence of cases. In this Perspective, we examine the case for a One Medicine approach to accelerate development of an effective therapy for rabies through the veterinary care and investigational treatment of naturally infected dogs in appropriate circumstances. We review the pathogenesis of rabies virus in humans and dogs, including recent advances in our understanding of the molecular basis for the severe neurological dysfunction. We propose that four categories of disease process need to be managed in patients: viral propagation, neuronal degeneration, inflammation and systemic compromise. Compassionate critical care and investigational treatment of naturally infected dogs receiving supportive therapy that mimics the human clinical scenario could increase opportunities to study combination therapies that address these processes, and to identify biomarkers for prognosis and therapeutic response. We discuss the safety and ethics of this approach, and introduce the Canine Rabies Treatment Initiative, a non-profit organization with the mission to apply a One Medicine approach to the investigation of diagnostic, prognostic, and therapeutic options for rabies in naturally infected dogs, to accelerate transformation of rabies into a treatable disease for all patients.

Rabies in Costa Rica - Next Steps Towards Controlling Bat-Borne Rabies After its Elimination in Dogs.

Rabies is an acute, progressive encephalitis caused by a lyssavirus, with the highest case fatality of any conventional infectious disease. More than 17 different lyssaviruses have been described, but rabies virus is the most widely distributed and important member of the genus. Globally, tens of thousands of human fatalities still occur each year. Although all mammals are susceptible, most human fatalities are caused by the bites of rabid dogs, within lesser developed countries. A global plan envisions the elimination of human rabies cases caused via dogs by the year 2030. The combination of prophylaxis of exposed humans and mass vaccination of dogs is an essential strategy for such success. Regionally, the Americas are well on the way to meet this goal. As one example of achievement, Costa Rica, a small country within Central America, reported the last autochthonous case of human rabies transmitted by a dog at the end of the 1970s. Today, rabies virus transmitted by the common vampire bat, Desmodus rotundus, as well as other wildlife, remains a major concern for humans, livestock, and other animals throughout the region. This review summarizes the historical occurrence of dog rabies and its elimination in Costa Rica, describes the current occurrence of the disease with a particular focus upon affected livestock, discusses the ecology of the vampire bat as the primary reservoir relevant to management, details the clinical characteristics of recent human rabies cases, and provides suggestions for resolution of global challenges posed by this zoonosis within a One Health context.

Towards Development of an Anti-Vampire Bat Vaccine for Rabies Management: Inoculation of Vampire Bat Saliva Induces Immune-Mediated Resistance.

The common vampire bat (Desmodus rotundus) is a hematophagous species responsible for paralytic rabies and bite damage that affects livestock, humans and wildlife from Mexico to Argentina. Current measures to control vampires, based upon coumarin-derived poisons, are not used extensively due in part to the high cost of application, risks for bats that share roosts with vampires and residual environmental contamination. Observations that vampire bat bites may induce resistance in livestock against vampire bat salivary anticoagulants encourage research into novel vaccine-based alternatives particularly focused upon increasing livestock resistance to vampire salivary components. We evaluated the action of vampire bat saliva-Freund's incomplete adjuvant administered to sheep with anticoagulant responses induced by repeated vampire bites in a control group and examined characteristics of vampire bat salivary secretion. We observed that injections induced a response against vampire bat salivary anticoagulants stronger than by repeated vampire bat bites. Based upon these preliminary findings, we hypothesize the utility of developing a control technique based on induction of an immunologically mediated resistance against vampire bat anticoagulants and rabies virus via dual delivery of appropriate host and pathogen antigens. Fundamental characteristics of host biology favor alternative strategies than simple culling by poisons for practical, economical, and ecologically relevant management of vampire populations within a One Health context.

Non-human primates as a reservoir for rabies virus in Brazil.

Rabies virus (RABV) does not persist in the environment as it is a very fragile agent. The primary hosts are mammalian species in the orders Carnivora and Chiroptera. Since the late 1980s, RABV has been isolated from non-human primates, Callithrix jacchus (the white-tufted marmoset), in four coastal states (Rio Grande do Norte, Ceará, Piauí and Pernambuco) in north-eastern Brazil, where this species is indigenous. The original habitat of C. jacchus consisted of two Brazilian biomes, the Atlantic Forest and the Caatinga. However, these marmosets have since adapted to other ecosystems as a result of human activities. Between 1988 and 1989, RABV isolates were obtained from white-tufted marmosets in the state of Rio Grande do Norte, but antigenic and genetic identification studies were not conducted at that time. In the following years, three additional states reported cases (Ceará, Piauí and Pernambuco). In two of these states (Ceará and Piauí), human cases of rabies transmitted by marmosets were reported. According to Brazilian Health Ministry data, at least 19 human cases in which this species was the source of infection were registered in between 1990 and 2016. Recent findings in laboratory tests of 12 rabid samples from humans and marmosets and the regional transmission among these animals for over 20 years, together with the gradual increase in the affected geographic area, support the concept of the emergence of a new RABV reservoir. Regional tourism, the wild animal trade and the cultural practice of maintaining these animals as pets, particularly in coastal regions, appear to be major risk factors for the increase in human cases. Additional epidemiological and ecological studies are required to better understand local disease dynamics and to identify ideal opportunities for prevention and control of this fatal infection.

Of bats and livestock: The epidemiology of rabies in Trinidad, West Indies.

Vampire bat-transmitted human rabies was first recognized in Trinidad during a major outbreak during the first half of the 20th century. To date, Trinidad is the only Caribbean island with vampire bat-transmitted rabies. Herein, we summarized the epidemiological situation of rabies in Trinidad during the period 1971-2015 through the analysis of field and laboratory records. During the study period, 259 domestic and wild animal rabies cases were laboratory confirmed with an annual median of 2 animal rabies cases. Over the 45 years, five significant epizootic events occurred (in 1974, 1997-1998, 2000, 2010 and 2012-2013) over which there was a significant increasing trend for the occurrence of rabies cases. The highest number of cases (87 cases) occurred during the 1997-1998 event, and the rabies positive proportion, was highest (0.7, 95% CI 0.52-0.84) for the year 2000. Rabies risk was highest for cattle (negative binomial parameter estimate 4.84, 95% CI 3.45-6.76), although numerous rabies cases were seen in the caprine population during the study period. In light of this finding, consideration should be given to including the small ruminant population in the national rabies vaccination program. Outbreaks affected mainly the counties of St. Patrick and St. George East, with epidemic progression outwards, and these areas should be prioritized for prevention and control efforts.

Non-human primates as a reservoir for rabies virus in Brazil

Rabies virus (RABV) does not persist in the environment as it is a very fragile agent. The primary hosts are mammalian species in the orders Carnivora and Chiroptera. Since the late 1980s, RABV has been isolated from non-human primates, Callithrix jacchus (the white-tufted marmoset), in four coastal states (Rio Grande do Norte, Ceará, Piauí and Pernambuco) in north-eastern Brazil, where this species is indigenous. The original habitat of C. jacchus consisted of two Brazilian biomes, the Atlantic Forest and the Caatinga. However, these marmosets have since adapted to other ecosystems as a result of human activities. Between 1988 and 1989, RABV isolates were obtained from white-tufted marmosets in the state of Rio Grande do Norte, but antigenic and genetic identification studies were not conducted at that time. In the following years, three additional states reported cases (Ceará, Piauí and Pernambuco). In two of these states (Ceará and Piauí), human cases of rabies transmitted by marmosets were reported. According to Brazilian Health Ministry data, at least 19 human cases in which this species was the source of infection were registered in between 1990 and 2016. Recent findings in laboratory tests of 12 rabid samples from humans and marmosets and the regional transmission among these animals for over 20 years, together with the gradual increase in the affected geographic area, support the concept of the emergence of a new RABV reservoir. Regional tourism, the wild animal trade and the cultural practice of maintaining these animals as pets, particularly in coastal regions, appear to be major risk factors for the increase in human cases. Additional epidemiological and ecological studies are required to better understand local disease dynamics and to identify ideal opportunities for prevention and control of this fatal infection.

Rabies in the Caribbean: A Situational Analysis and Historic Review.

Rabies virus is the only Lyssavirus species found in the Americas. In discussions about rabies, Latin America and the Caribbean are often grouped together. Our study aimed to independently analyse the rabies situation in the Caribbean and examine changes in rabies spatiotemporal epidemiology. A questionnaire was administered to the 33 member countries and territories of the Caribbean Animal Health Network (CaribVET) to collect current data, which was collated with a literature review. Rabies was endemic in ten Caribbean localities, with the dog, mongoose, and vampire bat identified as enzootic reservoirs. The majority of animal cases occurred in Puerto Rico, the Dominican Republic, and Haiti, while human cases only consistently occurred in the latter two areas. Rabies vaccination was conducted for high-risk animal populations with variable coverage, and rabies diagnostic capacities varied widely throughout the region. Illegal importation and natural migration of animals may facilitate the introduction of rabies virus variants into virus-naïve areas. Passive surveillance, together with enhanced methods and serological screening techniques, can therefore be of value. The insularity of the Caribbean makes it ideal for conducting pilot studies on reservoir host population management. Best practice guidelines developed for these reservoir hosts can be individually modified to the epidemiological status and available resources within each locality.

Non-human primates as a reservoir for rabies virus in Brazil

Rabies virus (RABV) does not persist in the environment as it is a very fragile agent. The primary hosts are mammalian species in the orders Carnivora and Chiroptera. Since the late 1980s, RABV has been isolated from non­human primates, Callithrix jacchus (the white­tufted marmoset), in four coastal states (Rio Grande do Norte, Ceará, Piauí and Pernambuco) in north­eastern Brazil, where this species is indigenous. The original habitat of C. jacchus consisted of two Brazilian biomes, the Atlantic Forest and the Caatinga. However, these marmosets have since adapted to other ecosystems as a result of human activities. Between 1988 and 1989, RABV isolates were obtained from white­tufted marmosets in the state of Rio Grande do Norte, but antigenic and genetic identification studies were not conducted at that time. In the following years, three additional states reported cases (Ceará, Piauí and Pernambuco). In two of these states (Ceará and Piauí), human cases of rabies transmitted by marmosets were reported. According to Brazilian Health Ministry data, at least 19 human cases in which this species was the source of infection were registered in between 1990 and 2016. Recent findings in laboratory tests of 12 rabid samples from humans and marmosets and the regional transmission among these animals for over 20 years, together with the gradual increase in the affected geographic area, support the concept of the emergence of a new RABV reservoir. Regional tourism, the wild animal trade and the cultural practice of maintaining these animals as pets, particularly in coastal regions, appear to be major risk factors for the increase in human cases. Additional epidemiological and ecological studies are required to better understand local disease dynamics and to identify ideal opportunities for prevention and control of this fatal infection. (AU)

Development and characterization of novel chimeric monoclonal antibodies for broad spectrum neutralization of rabies virus.

Current post-exposure prophylaxis for rabies virus infection has several limitations in terms of supply, cost, safety, and efficacy. Attempts to replace human or equine rabies immune globulins (HRIG or ERIG) have been made by several companies and institutes. We developed potent monoclonal antibodies to neutralize a broad spectrum of rabies viruses by screening hybridomas received from the U.S. Centers for Disease Control and Prevention (CDC). Two kinds of chimeric human antibodies (chimeric #7 and #17) were constructed by cloning the variable regions from selected hybridomas and the constant region of a human antibody. Two antibodies were bound to antigenic site III and I/IV, respectively, and were able to neutralize 51 field isolates of rabies virus that were isolated at different times and places such as Asia, Africa, North America, South America, and Australia. These two antibodies neutralize rabies viruses with high efficacy in an in vivo test using Syrian hamster and mouse models and show low risk for adverse immunogenicity.

The History of Rabies in Trinidad: Epidemiology and Control Measures.

Vampire bat-transmitted rabies was first recognized in Trinidad during a major outbreak reported in 1925. Trinidad is the only Caribbean island with vampire bat-transmitted rabies. We conducted a literature review to describe the changing epidemiology of rabies in Trinidad and give a historical perspective to rabies prevention and control measures on the island. The last human case of rabies occurred in 1937 and although no case of canine-transmitted rabies was reported since 1914, sporadic outbreaks of bat-transmitted rabies still occur in livestock to date. Over the last century, seven notable epidemics were recorded in Trinidad with the loss of over 3000 animals. During the 1950s, several measures were effectively adopted for the prevention and control of the disease which led to a significant reduction in the number of cases. These measures include: vampire bat population control, livestock vaccination, and animal surveillance. However, due to lapses in these measures over the years (e.g., periods of limited vampire control and incomplete herd vaccination), epidemics have occurred. In light of the significant negative impact of rabies on animal production and human health, rabies surveillance in Trinidad should be enhanced and cases evaluated towards the design and implementation of more evidence-based prevention and control programs.

Bat rabies in Guatemala.

Rabies in bats is considered enzootic throughout the New World, but few comparative data are available for most countries in the region. As part of a larger pathogen detection program, enhanced bat rabies surveillance was conducted in Guatemala, between 2009 and 2011. A total of 672 bats of 31 species were sampled and tested for rabies. The prevalence of rabies virus (RABV) detection among all collected bats was low (0.3%). Viral antigens were detected and infectious virus was isolated from the brains of two common vampire bats (Desmodus rotundus). RABV was also isolated from oral swabs, lungs and kidneys of both bats, whereas viral RNA was detected in all of the tissues examined by hemi-nested RT-PCR except for the liver of one bat. Sequencing of the nucleoprotein gene showed that both viruses were 100% identical, whereas sequencing of the glycoprotein gene revealed one non-synonymous substitution (302T,S). The two vampire bat RABV isolates in this study were phylogenetically related to viruses associated with vampire bats in the eastern states of Mexico and El Salvador. Additionally, 7% of sera collected from 398 bats demonstrated RABV neutralizing antibody. The proportion of seropositive bats varied significantly across trophic guilds, suggestive of complex intraspecific compartmentalization of RABV perpetuation.

Phylogenetic and epidemiologic evidence of multiyear incubation in human rabies.

Eight years after emigrating from Brazil, an otherwise healthy man developed rabies. An exposure prior to immigration was reported. Genetic analysis revealed a canine rabies virus variant found only in the patient's home country, and the patient had not traveled internationally since immigrating to the United States. We describe how epidemiological, phylogenetic, and viral sequencing data provided confirmation that rabies encephalomyelitis may present after a long, multiyear incubation period, a consideration that previously has been hypothesized without the ability to exclude a more recent exposure. Accordingly, rabies should be considered in the diagnosis of any acute encephalitis, myelitis, or encephalomyelitis.

New world bats harbor diverse influenza A viruses.

Aquatic birds harbor diverse influenza A viruses and are a major viral reservoir in nature. The recent discovery of influenza viruses of a new H17N10 subtype in Central American fruit bats suggests that other New World species may similarly carry divergent influenza viruses. Using consensus degenerate RT-PCR, we identified a novel influenza A virus, designated as H18N11, in a flat-faced fruit bat (Artibeus planirostris) from Peru. Serologic studies with the recombinant H18 protein indicated that several Peruvian bat species were infected by this virus. Phylogenetic analyses demonstrate that, in some gene segments, New World bats harbor more influenza virus genetic diversity than all other mammalian and avian species combined, indicative of a long-standing host-virus association. Structural and functional analyses of the hemagglutinin and neuraminidase indicate that sialic acid is not a ligand for virus attachment nor a substrate for release, suggesting a unique mode of influenza A virus attachment and activation of membrane fusion for entry into host cells. Taken together, these findings indicate that bats constitute a potentially important and likely ancient reservoir for a diverse pool of influenza viruses.

Concomitant administration of GonaCon™ and rabies vaccine in female dogs (Canis familiaris) in Mexico.

Mexico serves as a global model for advances in rabies prevention and control in dogs. The Mexican Ministry of Health (MMH) annual application of approximately 16 million doses of parenteral rabies vaccine has resulted in significant reductions in canine rabies during the past 20 years. One collateral parameter of rabies programs is dog population management. Enhanced public awareness is critical to reinforce responsible pet ownership. Surgical spaying and neutering remain important to prevent reproduction, but are impractical for achieving dog population management goals. GonaCon™, an anti-gonadotropin releasing hormone (GnRH) vaccine, was initially tested in captive female dogs on the Navajo Nation, 2008. The MMH led this international collaborative study on an improved formulation of GonaCon™ in captive dogs with local representatives in Hidalgo, Mexico in 2011. This study contained 20 bitches assigned to Group A (6 control), Group B (7 GonaCon™), and Group C (7 GonaCon™ and rabies vaccine). Vaccines were delivered IM. Animals were placed under observation and evaluated during the 61-day trial. Clinically, all dogs behaved normally. No limping or prostration was observed, in spite of minor muscle atrophy post-mortem in the left hind leg of dogs that received GonaCon™. Two dogs that began the study pregnant give birth to healthy pups. Dogs that received a GonaCon™ injection had macro and microscopic lesions consistent with prior findings, but the adverse injection effects were less frequent and lower in intensity. Both vaccines were immunogenic based on significant increases in rabies virus neutralizing antibodies and anti-GnRH antibodies in treatment Groups B and C. Simultaneous administration of GonaCon™ and rabies vaccine in Group C did not affect immunogenicity. Progesterone was suppressed significantly in comparison to controls. Future studies that monitor fertility through multiple breeding cycles represent a research need to determine the value of integrating this vaccine into dog rabies management.

Prevalence of neutralizing antibodies to rabies virus in serum of seven species of insectivorous bats from Colorado and New Mexico, United States.

We determined the presence of rabies-virus-neutralizing antibodies (RVNA) in serum of 721 insectivorous bats of seven species captured, sampled, and released in Colorado and New Mexico, United States in 2003-2005. A subsample of 160 bats was tested for rabies-virus RNA in saliva. We sampled little brown bats (Myotis lucifugus) at two maternity roosts in Larimer County, Colorado; big brown bats (Eptesicus fuscus) at three maternity roosts in Morgan County, Colorado; and big brown bats at five maternity roosts in Larimer County. We also sampled hoary bats (Lasiurus cinereus) and silver-haired bats (Lasionycteris noctivagans) captured while drinking or foraging over water in Bernalillo County, New Mexico and at various locations in Larimer County. Big brown bats, little brown bats, long-legged myotis (Myotis volans), long-eared myotis (Myotis evotis), and fringed myotis (Myotis thysanodes) were also sampled over water in Larimer County. All species except long-eared myotis included individuals with RVNA, with prevalences ranging from 7% in adult female silver-haired bats to 32% in adult female hoary bats. None of the bats had detectable rabies-virus RNA in oropharyngeal swabs, including 51 bats of 5 species that had RVNA in serum. Antibody-positive bats were present in nine of the 10 maternity colonies sampled. These data suggest that wild bats are commonly exposed to rabies virus and develop a humoral immune response suggesting some degree of viral replication, but many infections fail to progress to clinical disease.

Discovery of diverse polyomaviruses in bats and the evolutionary history of the Polyomaviridae.

Polyomaviruses (PyVs) have been identified in a wide range of avian and mammalian species. However, little is known about their occurrence, genetic diversity and evolutionary history in bats, even though bats are important reservoirs for many emerging viral pathogens. This study screened 380 specimens from 35 bat species from Kenya and Guatemala for the presence of PyVs by semi-nested pan-PyV PCR assays. PyV DNA was detected in 24 of the 380 bat specimens. Phylogenetic analysis revealed that the bat PyV sequences formed 12 distinct lineages. Full-genome sequences were obtained for seven representative lineages and possessed similar genomic features to known PyVs. Strikingly, this evolutionary analysis revealed that the bat PyVs were paraphyletic, suggestive of multiple species jumps between bats and other mammalian species, such that the theory of virus-host co-divergence for mammalian PyVs as a whole could be rejected. In addition, evidence was found for strong heterogeneity in evolutionary rate and potential recombination in a number of PyV complete genomes, which complicates both phylogenetic analysis and virus classification. In summary, this study revealed that bats are important reservoirs of PyVs and that these viruses have a complex evolutionary history.

Rabies surveillance in the United States during 2011.

During 2011, 49 states and Puerto Rico reported 6,031 rabid animals and 6 human rabies cases to the CDC, representing a 1.9% decrease from the 6,153 rabid animals and 2 human cases reported in 2010. Approximately 92% of reported rabid animals were wildlife. Relative contributions by the major animal groups were as follows: 1,981 raccoons (32.8%), 1,627 skunks (27.0%), 1,380 bats (22.9%), 427 foxes (7.1%), 303 cats (5.0%), 65 cattle (1.1%), and 70 dogs (1.2%). Compared with 2010, there was a substantial increase in the number of rabid skunks reported. Six cases of rabies involving humans were reported from California, Massachusetts, New Jersey, New York, and South Carolina. Three cases reported from Massachusetts, New Jersey, and New York were determined to be a result of canine rabies virus variants acquired outside the United States.

Ecological and anthropogenic drivers of rabies exposure in vampire bats: implications for transmission and control.

Despite extensive culling of common vampire bats in Latin America, lethal human rabies outbreaks transmitted by this species are increasingly recognized, and livestock rabies occurs with striking frequency. To identify the individual and population-level factors driving rabies virus (RV) transmission in vampire bats, we conducted a longitudinal capture-recapture study in 20 vampire bat colonies spanning four regions of Peru. Serology demonstrated the circulation of RV in vampire bats from all regions in all years. Seroprevalence ranged from 3 to 28 per cent and was highest in juvenile and sub-adult bats. RV exposure was independent of bat colony size, consistent with an absence of population density thresholds for viral invasion and extinction. Culling campaigns implemented during our study failed to reduce seroprevalence and were perhaps counterproductive for disease control owing to the targeted removal of adults, but potentially greater importance of juvenile and sub-adult bats for transmission. These findings provide new insights into the mechanisms of RV maintenance in vampire bats and highlight the need for ecologically informed approaches to rabies prevention in Latin America.

A distinct lineage of influenza A virus from bats.

Influenza A virus reservoirs in animals have provided novel genetic elements leading to the emergence of global pandemics in humans. Most influenza A viruses circulate in waterfowl, but those that infect mammalian hosts are thought to pose the greatest risk for zoonotic spread to humans and the generation of pandemic or panzootic viruses. We have identified an influenza A virus from little yellow-shouldered bats captured at two locations in Guatemala. It is significantly divergent from known influenza A viruses. The HA of the bat virus was estimated to have diverged at roughly the same time as the known subtypes of HA and was designated as H17. The neuraminidase (NA) gene is highly divergent from all known influenza NAs, and the internal genes from the bat virus diverged from those of known influenza A viruses before the estimated divergence of the known influenza A internal gene lineages. Attempts to propagate this virus in cell cultures and chicken embryos were unsuccessful, suggesting distinct requirements compared with known influenza viruses. Despite its divergence from known influenza A viruses, the bat virus is compatible for genetic exchange with human influenza viruses in human cells, suggesting the potential capability for reassortment and contributions to new pandemic or panzootic influenza A viruses.

Rabies surveillance in the United States during 2010.

During 2010, 48 states and Puerto Rico reported 6,154 rabid animals and 2 human rabies cases to the CDC, representing an 8% decrease from the 6,690 rabid animals and 4 human cases reported in 2009. Hawaii and Mississippi did not report any laboratory-confirmed rabid animals during 2010. Approximately 92% of reported rabid animals were wildlife. Relative contributions by the major animal groups were as follows: 2,246 raccoons (36.5%), 1,448 skunks (23.5%), 1,430 bats (23.2%), 429 foxes (6.9%), 303 cats (4.9%), 71 cattle (1.1 %), and 69 dogs (1.1 %). Compared with 2009, number of reported rabid animals decreased across all animal types with the exception of a 1 % increase in the number of reported rabid cats. Two cases of rabies involving humans were reported from Louisiana and Wisconsin in 2010. Louisiana reported an imported human rabies case involving a 19-year-old male migrant farm worker who had a history of a vampire bat (Desmodus rotundus) bite received while in Mexico. This represents the first human rabies case reported in the United States confirmed to have been caused by a vampire bat rabies virus variant. Wisconsin reported a human rabies case involving a 70-year-old male that was confirmed to have been caused by a rabies virus variant associated with tri-colored bats (Perimyotis subflavus).