3Rs implementation in veterinary vaccine batch-release testing: Current state-of-the-art and future opportunities. A webinar and workshop report.

Regulatory authorities require veterinary batch-release testing to confirm vaccine potency and safety, but these tests have traditionally relied on large numbers of laboratory animals. Advances in vaccine research and development offer increasing opportunities to replace in vivo testing, and some stakeholders have made significant progress in incorporating 3Rs elements in quality control strategies. A three-part event series entitled "3Rs Implementation in Veterinary Vaccine Batch-Release Testing: Current state-of-the-art and future opportunities" was jointly organized by the Animal-Free Safety Assessment Collaboration, HealthforAnimals, and the International Alliance of Biological Standardization. Two webinars and a workshop aimed to outline the state-of-the-art non-animal approaches for veterinary batch-release testing. The events included information on the state of the deletion of obsolete safety testing and the current initiatives implemented by European, North American, and Asian-Pacific stakeholders on 3Rs implementation and regulatory acceptance. The events contributed to a better understanding of the barriers to 3Rs implementation. Participants highlighted the need for open communication, continued collaboration between stakeholders, and international harmonization of regulatory requirements to help accelerate acceptance. Despite the challenges, the countries represented at this three-part event have shared their commitments to advancing the acceptance of alternative methods.

Quantitative risk assessment of rabies being introduced into mainland France through worldwide noncommercial dog and cat movements.

France has been rabies-free among nonflying mammals since 2001. Despite this status, the rabies virus has been introduced several times through noncommercial pet movements, posing a threat of infection by this 100%-lethal zoonosis among local animal and human populations. To quantify the risk of rabies being introduced through worldwide noncommercial dog and cat movements, we performed a quantitative risk assessment using stochastic scenario tree modeling. The mean annual probability of at least one rabies introduction incident was 0.35 (median: 0.24, 90% prediction interval (PI) [0.04; 0.98]) and the mean annual number of rabies-infected pets introduced through pet movements was 0.96 (median: 0.27, 90% PI [0.04; 3.88]). These results highlight a nonnegligible, even high risk due to the associated consequences of such events. In alternative scenario testing, preventive anti-rabies vaccination proved to be an effective measure since removing the vaccination requirement led to a > 15-fold increase in risk. The serological testing requirement had less of an effect (approximately two-fold increase when removed) and the posttest waiting period to ensure that antibodies were not linked to an infection had a negligible effect. Any change in pet owner compliance, especially regarding vaccination, could have a major impact on the risk. This study also shows that reinforced border control staff training could be more effective in reducing risk than more frequent checks. These results provide quantitative data for assessing the probability of the rabies virus entering France, and could help policymakers decrease this risk in rabies-free areas.

Comparison of intra- and inter-host genetic diversity in rabies virus during experimental cross-species transmission.

The development of high-throughput genome sequencing enables accurate measurements of levels of sub-consensus intra-host virus genetic diversity and analysis of the role played by natural selection during cross-species transmission. We analysed the natural and experimental evolution of rabies virus (RABV), an important example of a virus that is able to make multiple host jumps. In particular, we (i) analyzed RABV evolution during experimental host switching with the goal of identifying possible genetic markers of host adaptation, (ii) compared the mutational changes observed during passage with those observed in natura, and (iii) determined whether the colonization of new hosts or tissues requires adaptive evolution in the virus. To address these aims, animal infection models (dog and fox) and primary cell culture models (embryo brain cells of dog and fox) were developed and viral variation was studied in detail through deep genome sequencing. Our analysis revealed a strong unidirectional host evolutionary effect, as dog-adapted rabies virus was able to replicate in fox and fox cells relatively easily, while dogs or neuronal dog cells were not easily susceptible to fox adapted-RABV. This suggests that dog RABV may be able to adapt to some hosts more easily than other host variants, or that when RABV switched from dogs to red foxes it lost its ability to adapt easily to other species. Although no difference in patterns of mutation variation between different host organs was observed, mutations were common following both in vitro and in vivo passage. However, only a small number of these mutations also appeared in natura, suggesting that adaptation during successful cross-species virus transmission is a complex, multifactorial evolutionary process.

Role of Oral Rabies Vaccines in the Elimination of Dog-Mediated Human Rabies Deaths.

Domestic dogs are responsible for nearly all the ¼59,000 global human rabies deaths that occur annually. Numerous control measures have been successful at eliminating dog-mediated human rabies deaths in upper-income countries, including dog population management, parenteral dog vaccination programs, access to human rabies vaccines, and education programs for bite prevention and wound treatment. Implementing these techniques in resource-poor settings can be challenging; perhaps the greatest challenge is maintaining adequate herd immunity in free-roaming dog populations. Oral rabies vaccines have been a cornerstone in rabies virus elimination from wildlife populations; however, oral vaccines have never been effectively used to control dog-mediated rabies. Here, we convey the perspectives of the World Organisation for Animal Health Rabies Reference Laboratory Directors, the World Organisation for Animal Health expert committee on dog rabies control, and World Health Organization regarding the role of oral vaccines for dogs. We also issue recommendations for overcoming hesitations to expedited field use of appropriate oral vaccines.

Detection of rabies antibodies in wild boars in north-east Romania by a rabies ELISA test.

BACKGROUND: In the last few decades, Romania has been considered one of the European countries most affected by animal rabies, but a combination of oral rabies vaccination (ORV) campaigns in foxes alongside mandatory vaccination of pets has substantially decreased the number of rabies cases in recent years. The objective of this study was to detect rabies antibodies in wild boar serum and thoracic fluid samples collected during the hunting season after ORV campaigns in north-eastern Romania in order to identify if wild boars are substantial competitors to foxes for ORV baits. RESULTS: When the 312 wild boar samples were tested by ELISA (BioPro ELISA, Czech Republic), 42.31% (132/312) demonstrated rabies antibodies. In order to compare these wild boar results in terms of the percentage of immunisation, fox samples were also included in the study, and in this case only 28.40% (98/345) demonstrated rabies antibodies by ELISA. To check the diagnostic sensitivity and specificity of this ELISA, those samples with a sufficient volume from both species that had tested either negative or positive with an initial ELISA were then tested with the Fluorescent Antibody Virus Neutralisation (FAVN) assay. The overall concordance between the BioPro ELISA and FAVN test was 74.26% (75/101) in wild boar samples and 65.66% (65/99) in fox samples, 140 out of 200 samples being correlated with the two methods, although no significant statistical difference (p = 0.218) between the two species was registered. We found a good agreement by both tests for the ELISA-positive samples (91.30%), however the situation was different for the ELISA-negative samples, where a low agreement was demonstrated (41.18%). CONCLUSIONS: This study reports for the first time the presence of rabies antibodies in wild boar samples collected during the hunting season in Romania after ORV campaigns in rabies endemic areas. It is also the first study to demonstrate that ELISA BioPro can be used on wild boar samples with satisfactory results compared to the FAVN test for this species.

Oral vaccination of dogs: a well-studied and undervalued tool for achieving human and dog rabies elimination.

The mass vaccination of dogs is a proven tool for rabies prevention. Besides parenteral delivery of inactivated vaccines, over the past several decades, several self-replicating biologics, including modified-live, attenuated and recombinant viruses, have been evaluated for the oral vaccination of dogs against rabies. Vaccines are included within an attractive bait for oral consumption by free-ranging dogs. Due to the high affinity between dogs and humans, such biologics intended for oral vaccination of dogs (OVD) need to be efficacious as well as safe. Baits should be preferentially attractive to dogs and not to non-target species. Although many different types have been evaluated successfully, no universal bait has been identified to date. Moreover, high bait acceptance does not necessarily mean that vaccine efficacy and programmatic success is predictable. The use of OVD in the laboratory and field has demonstrated the safety and utility of this technology. Within a One Health context, OVD should be considered as part of a holistic plan for the global elimination of canine rabies.

Correction to: Oral vaccination of dogs: a well-studied and undervalued tool for achieving human and dog rabies elimination.

The original article [1] contained an error in the Author details paragraph. "5Neglected Zoonotic Diseases, World Health Organization, Geneva, Switzerland" should be replaced by "5Le Grand-Saconnex, Switzerland".

Molecular and serological survey of lyssaviruses in Croatian bat populations.

BACKGROUND: Rabies is the only known zoonotic disease of bat origin in Europe. The disease is caused by species belonging to the genus Lyssavirus. Five Lyssavirus species, i.e., European bat lyssavirus (EBLV)-1, EBLV-2, Bokeloh bat lyssavirus, Lleida bat lyssavirus, and West Caucasian bat virus, have been identified in European bats. More recently, a proposed sixth species, Kotalahti bat lyssavirus, was detected. Thus, in this study, active surveillance was initiated in order to obtain insights into the prevalence of lyssaviruses in Croatian bat populations and to improve our understanding of the public health threat of infected bats. RESULTS: In total, 455 bats were caught throughout Continental and Mediterranean Croatia. Antibodies were found in 20 of 350 bats (5.71%, 95% confidence interval 3.73-8.66). The majority of seropositive bats were found in Trbusnjak cave (Continental Croatia, Eastern part), and most seropositive bats belonged to Myotis myotis (13/20). All oropharyngeal swabs were negative for the presence of Lyssavirus. CONCLUSIONS: The presence of lyssaviruses in bat populations was confirmed for the first time in Croatia and Southeastern Europe. The results of this study suggest the need for further comprehensive analyses of lyssaviruses in bats in this part of Europe.

Potentially Zoonotic Bartonella in Bats from France and Spain.

We detected Bartonella in 11 of 109 insectivorous bats from France and 1 of 26 bats from Spain. These genetic variants are closely related to bat-associated Bartonella described in Finland and the United Kingdom and to B. mayotimonensis, the agent of a human endocarditis case in the United States.

Oral vaccination of wildlife using a vaccinia-rabies-glycoprotein recombinant virus vaccine (RABORAL V-RG®): a global review.

RABORAL V-RG® is an oral rabies vaccine bait that contains an attenuated ("modified-live") recombinant vaccinia virus vector vaccine expressing the rabies virus glycoprotein gene (V-RG). Approximately 250 million doses have been distributed globally since 1987 without any reports of adverse reactions in wildlife or domestic animals since the first licensed recombinant oral rabies vaccine (ORV) was released into the environment to immunize wildlife populations against rabies. V-RG is genetically stable, is not detected in the oral cavity beyond 48 h after ingestion, is not shed by vaccinates into the environment, and has been tested for thermostability under a range of laboratory and field conditions. Safety of V-RG has been evaluated in over 50 vertebrate species, including non-human primates, with no adverse effects observed regardless of route or dose. Immunogenicity and efficacy have been demonstrated under laboratory and field conditions in multiple target species (including fox, raccoon, coyote, skunk, raccoon dog, and jackal). The liquid vaccine is packaged inside edible baits (i.e., RABORAL V-RG, the vaccine-bait product) which are distributed into wildlife habitats for consumption by target species. Field application of RABORAL V-RG has contributed to the elimination of wildlife rabies from three European countries (Belgium, France and Luxembourg) and of the dog/coyote rabies virus variant from the United States of America (USA). An oral rabies vaccination program in west-central Texas has essentially eliminated the gray fox rabies virus variant from Texas with the last case reported in a cow during 2009. A long-term ORV barrier program in the USA using RABORAL V-RG is preventing substantial geographic expansion of the raccoon rabies virus variant. RABORAL V-RG has also been used to control wildlife rabies in Israel for more than a decade. This paper: (1) reviews the development and historical use of RABORAL V-RG; (2) highlights wildlife rabies control programs using the vaccine in multiple species and countries; and (3) discusses current and future challenges faced by programs seeking to control or eliminate wildlife rabies.

Bat rabies surveillance in France: first report of unusual mortality among serotine bats.

BACKGROUND: Rabies is a fatal viral encephalitic disease that is caused by lyssaviruses which can affect all mammals, including human and bats. In Europe, bat rabies cases are attributed to five different lyssavirus species, the majority of rabid bats being attributed to European bat 1 lyssavirus (EBLV-1), circulating mainly in serotine bats (Eptesicus serotinus). In France, rabies in bats is under surveillance since 1989, with 77 positive cases reported between 1989 and 2016. CASE PRESENTATION: In the frame of the bat rabies surveillance, an unusual mortality of serotine bats was reported in 2009 in a village in North-East France. Six juvenile bats from an E. serotinus maternity colony counting ~200 individuals were found to be infected with EBLV-1. The active surveillance of the colony by capture sessions of bats from July to September 2009 showed a high detection rate of neutralising EBLV-1 antibodies (≈ 50%) in the colony. Moreover, one out of 111 animals tested was found to shed viable virus in saliva, while lyssavirus RNA was detected by RT-PCR for five individuals. CONCLUSION: This study demonstrated that the lyssavirus infection in the serotine maternity colony was followed by a high rate of bat rabies immunity after circulation of the virus in the colony. The ratio of seropositive bats is probably indicative of an efficient virus transmission coupled to a rapid circulation of EBLV-1 in the colony.

First detection of European bat lyssavirus type 2 (EBLV-2) in Norway.

BACKGROUND: In Europe, bat rabies is primarily attributed to European bat lyssavirus type 1 (EBLV-1) and European bat lyssavirus type 2 (EBLV-2) which are both strongly host-specific. Approximately thirty cases of infection with EBLV-2 in Daubenton's bats (Myotis daubentonii) and pond bats (M. dasycneme) have been reported. Two human cases of rabies caused by EBLV-2 have also been confirmed during the last thirty years, while natural spill-over to other non-flying mammals has never been reported. Rabies has never been diagnosed in mainland Norway previously. CASE PRESENTATION: In late September 2015, a subadult male Daubenton's bat was found in a poor condition 800 m above sea level in the southern part of Norway. The bat was brought to the national Bat Care Centre where it eventually displayed signs of neurological disease and died after two days. EBLV-2 was detected in brain tissues by polymerase chain reaction (PCR) followed by sequencing of a part of the nucleoprotein gene, and lyssavirus was isolated in neuroblastoma cells. CONCLUSIONS: The detection of EBLV-2 in a bat in Norway broadens the knowledge on the occurrence of this zoonotic agent. Since Norway is considered free of rabies, adequate information to the general public regarding the possibility of human cases of bat-associated rabies should be given. No extensive surveillance of lyssavirus infections in bats has been conducted in the country, and a passive surveillance network to assess rabies prevalence and bat epidemiology is highly desired.

Travel-Associated Rabies in Pets and Residual Rabies Risk, Western Europe.

In 2015, countries in western Europe were declared free of rabies in nonflying mammals. Surveillance data for 2001-2013 indicate that risk for residual rabies is not 0 because of pet importation from countries with enzootic rabies. However, the risk is so low (7.52 × 10(-10)) that it probably can be considered negligible.

Molecular Characterization of Canine Rabies Virus, Mali, 2006-2013.

We genetically characterized 32 canine rabies viruses isolated in Mali during 2006-2013 and identified 3 subgroups that belonged to the Africa 2 lineage. We also detected subgroup F rabies virus. This information should be useful for development of mass vaccination campaigns for dogs and eventual large-scale control programs in this country.

A step forward in the quality control testing of inactivated rabies vaccines - extensive evaluation of European vaccines by using alternative methods to the in vivo potency tests.

The mouse challenge test still remains the reference method for the potency determination of human and animal inactivated rabies vaccines, and it is still widely used throughout the world. This test suffers from many disadvantages - it is expensive and time consuming, uses a large number of mice, causes significant animal distress, and suffers from high variability. Recently, the European Pharmacopoeia has recognised the use of a serological potency assay (SPA) as an alternative method to the challenge test. This new test is based on the determination of rabies neutralising antibody titres in vaccinated mice, by using the modified Rapid Fluorescent Focus Inhibition Test (mRFFIT). With the objective of adopting this new method for the batch release of inactivated rabies vaccines, we evaluated its performance on a large collection of rabies vaccines currently assessed in our laboratory. The Fluorescent Antibody Virus Neutralisation test (FAVNt) was used in parallel with the mRFFIT, and the results were compared to the mouse challenge test. Our results demonstrate that the SPA is capable of estimating the potency of vaccines formulated with a potency margin well above the minimum of 1IU/dose. For low potency vaccines, this new method demonstrated some limitations, due to the recurrent invalidation of the assay. We have also demonstrated the superior sensitivity of the FAVNt when compared to the mRFFIT, and the importance of minimising the risk of detecting non-responders in vaccinated mice.

Twenty year experience of the oral rabies vaccine SAG2 in wildlife: a global review.

The SAG2 vaccine (RABIGEN® SAG2) is a modified live attenuated rabies virus vaccine, selected from the SAD Bern strain in a two-step process of amino acid mutation using neutralizing monoclonal antibodies. The strain is genetically stable and does not spread in vivo or induce a persistent infection. Its absence of residual pathogenicity was extensively demonstrated in multiple target and non target species (such as wild carnivores and rodent species), including non-human primates. The efficacy of SAG2 baits was demonstrated according to the EU requirements for the red fox and raccoon dog. The use of safe and potent rabies vaccines such as SAG2 largely contributed to the elimination of rabies in Estonia, France, Italy and Switzerland. Importantly, these countries were declared free of rabies after few years of oral vaccination campaigns with SAG2 baits distributed with an appropriate strategy. The excellent tolerance of the SAG2 vaccine has been confirmed in the field since its first use in 1993. No safety issues have been reported, and in particular no vaccine-induced rabies cases were diagnosed, after the distribution of more than 20 million SAG2 baits in Europe.

What would be the impact on the rabies risk of reducing the waiting period before dogs are imported? A modelling study based on the European Union legislation.

AIMS: Lyssavirus rabies (RABV) is responsible for a major zoonotic infection that is almost always lethal once clinical signs appear. Rabies can be (re)introduced into rabies-free areas through transboundary dog movements, thus compromising animal and human health. A number of measures have been implemented to prevent this happening, one of which is the waiting period (WP) after anti-rabies vaccination and serological testing. This WP ensures that antibodies assessed through the serological test are due to the vaccine, not to infection. Indeed, if antibodies are due to RABV infection, the dog should display clinical signs within this WP and would not therefore be imported. METHODS AND RESULTS: Within a framework of quantitative risk assessment, we used modelling approaches to evaluate the impact of this WP and its duration on the risk of introducing rabies via the importation of dogs into the European Union. Two types of models were used, a classical stochastic scenario tree model and an individual-based model, both parameterised using scientific literature or data specifically applicable to the EU. Results showed that, assuming perfect compliance, the current 3-month waiting period was associated with a median annual number of 0.04 infected dogs imported into the EU. When the WP was reduced, the risk increased. For example, for a 1-month WP, the median annual number of infected dogs imported was 0.17 or 0.15 depending on the model, which corresponds to a four-fold increase. CONCLUSION: This in silico study, particularly suitable for evaluating rare events such as rabies infections in rabies-free areas, provided results that can directly inform policymakers in order to adapt regulations linked to rabies and animal movements.

A Global Perspective on Oral Vaccination of Wildlife against Rabies.

The long-term mitigation of human-domestic animal-wildlife conflicts is complex and difficult. Over the last 50 yr, the primary biomedical concepts and actualized collaborative global field applications of oral rabies vaccination to wildlife serve as one dramatic example that revolutionized the field of infectious disease management of free-ranging animals. Oral vaccination of wildlife occurred in diverse locales within Africa, Eurasia, the Middle East, and North America. Although rabies is not a candidate for eradication, over a billion doses of vaccine-laden baits distributed strategically by hand, at baiting stations, or via aircraft, resulted in widespread disease prevention, control, or local disease elimination among mesocarnivores. Pure, potent, safe, and efficacious vaccines consisted of either modified-live, highly attenuated, or recombinant viruses contained within attractive, edible baits. Since the late 1970s, major free-ranging target species have included coyotes (Canis latrans), foxes (Urocyon cinereoargenteus; Vulpes vulpes), jackals (Canis aureus; Lupulella mesomelas), raccoons (Procyon lotor), raccoon dogs (Nyctereutes procyonoides), and skunks (Mephitis mephitis). Operational progress has occurred in all but the latter species. Programmatic evaluations of oral rabies vaccination success have included: demonstration of biomarkers incorporated within vaccine-laden baits in target species as representative of bait contact; serological measurement of the induction of specific rabies virus neutralizing antibodies, indicative of an immune response to vaccine; and most importantly, the decreasing detection of rabies virus antigens in the brains of collected animals via enhanced laboratory-based surveillance, as evidence of management impact. Although often conceived mistakenly as a panacea, such cost-effective technology applied to free-ranging wildlife represents a real-world, One Health application benefiting agriculture, conservation biology, and public health. Based upon lessons learned with oral rabies vaccination of mesocarnivores, opportunities for future extension to other taxa and additional diseases will have far-reaching, transdisciplinary benefits.

Evaluation of Bait Acceptance and Immune Response in Local Dogs during an Oral Rabies Vaccination Field Study in Morocco.

The objective of this study was to evaluate the bait preference of three selected bait types by local dogs and the induced immunogenicity of the oral rabies vaccine strain SPBN GASGAS in Morocco. The vaccine strain, combined with different bait types, has been tested in many different settings, but not yet in northern Africa. Overall, bait consumption and preference were similar in other studies using the same materials (bait type and sachet). The intestine bait had the highest acceptance rate (97.6%, 95%CI: 87.4-99.9), followed by the egg bait (83.0%, 95%CI: 69.2-92.4). Only 52% (95%CI: 37.4-66.3) of the dogs showed an interest in the fish meal bait. However, considering the successful release of the contents of the sachet (blue-dyed water) into the oral cavity, the egg bait (65.7%, 95%CI: 47.8-80.9) scored better than the intestine bait (51.7%, 95%CI: 32.5-70.6). The dogs selected for the immunogenicity study were offered the egg bait containing a sachet filled with SPBN GASGAS (3.0 mL, 107.5 FFU/mL) or were given the same dose by direct oral administration (d.o.a.). In addition, several dogs were vaccinated by the parenteral route (s.c.) using a commercially available inactivated rabies vaccine. Unfortunately, due to the COVID-19 pandemic and subsequent travel restrictions, it was not possible to collect blood samples directly after vaccination. The blood samples were collected pre-vaccination and on five occasions between 450 and 1088 days post vaccination. The seroconversion rate, as determined for rabies-virus-neutralizing antibodies by the FAVN test, was significantly lower than that found for binding antibodies, as determined by ELISA, for all blood samples collected post vaccination. No treatment effect (bait, d.o.a., s.c.) could be seen in the seroconversion rate. At 15 months post vaccination, 84.2% of the dogs offered vaccine bait still tested sero-positive in ELISA. Only after 3 years was a clear drop in the seroconversion rate observed in all three treatment groups. This study confirms the long-term immunogenicity of the oral rabies vaccine SPBN GASGAS in dogs under field conditions.

Isolation of Bokeloh bat lyssavirus in Myotis nattereri in France.

Bokeloh bat lyssavirus (BBLV) was found in Myotis nattereri for the first time in northeastern France in July 2012. The complete genome sequence of the virus from the infected Natterer's bat was determined by whole-genome sequencing and compared to that of the first BBLV strain isolated in 2010 in Germany and with those of all currently identified lyssaviruses. The French isolate [KC169985] showed 98.7 % nucleotide sequence identity to the German BBLV strain [JF311903]. Several organs of the infected French bat were examined by classical rabies diagnostic methods: fluorescent antibody test, cell culture inoculation test and RT-qPCR. Antigen, infectious virus and high viral RNA levels were found in both the brain and salivary glands. Traces of genomic RNA were detected in the bladder, kidney and lung tissue. The results of an investigation of the distribution of lyssaviruses with the detection of infectious virus in the salivary glands suggest a possible mode of transmission of the virus.