Oral Rabies Vaccination Campaigns Research Articles

Retrospective analysis of sero-prevalence and bait uptake estimations in foxes after oral rabies vaccination programmes at European level: Lessons learned and paths forward

Rabies caused by the Classical Rabies Virus (Lyssavirus rabies abbreviated RABV) in the European Union has been close to elimination mainly thanks to Oral Rabies Vaccination (ORV) campaigns targeting wildlife (primarily red foxes). ORV programmes co-financed by the European Commission include a monitoring-component to assess the effectiveness of the ORV campaigns at national level. This assessment is performed by a random collection of red foxes in the vaccinated areas with control of antibodies presence by serological analysis and control of bait uptake by detection of biomarkers (tetracycline incorporated into the baits) in the bones and teeth. ORV programmes aim to a vaccine coverage high enough to immunize (ideally) 70 % of the reservoir population to control the spread of the disease. European Union (EU) programmes that led to almost elimination of rabies on the territory have been traditionally found to have a bait uptake average of 70 % (EU countries; 2010–2020 period) while the seroconversion data showed an average level of 40 % (EU countries; 2010–2020 period). To better understand variations of these indicators, a study was been set up to evaluate the impact of several variables (linked to the vaccination programme itself and linked to environmental conditions) on the bait uptake and the seroconversion rate. Thus, pooling data from several countries provides more powerful statistics and the highest probability of detecting trends. Results of this study advocate the use of a single serological test across the EU since data variation due to the type of test used was higher than variations due to field factors, making the interpretation of monitoring results at EU level challenging. In addition, the results indicates a negative correlation between bait uptake and maximum temperatures reached during ORV campaigns questioning the potential impact of climatic change and associated increase of temperatures on the ORV programmes efficiency. Several hypotheses requesting additional investigation are drawn and discussed in this paper.

Epidemiological Interface of Sylvatic and Dog Rabies in the North West Province of South Africa.

Rabies is a viral zoonosis that causes an estimated 59,000 preventable human fatalities every year. While more than 120 countries remain endemic for dog-mediated rabies, the burden is the highest in Africa and Asia where 99% of human rabies cases are caused by domestic dogs. One such rabies-endemic country is South Africa where an estimated 42 preventable human deaths occur every year. Although canine rabies had been well described for most of the provinces in South Africa, the epidemiology of rabies within the North West Province had not been well defined prior to this investigation. As such, the aim of this study was to use nucleotide sequence analyses to characterise the extant molecular epidemiology of rabies in the North West Province of South Africa—with specific focus on the interface between dogs and sylvatic species. To this end, Rabies lyssavirus isolates originating from the North West Province were subjected to molecular epidemiological analyses relying on the Bayesian Markov Chain Monte Carlo methodology on two distinct gene regions, viz. the G-L intergenic region and partial nucleoprotein gene. Our results provided strong evidence in support of an endemic cycle of canine rabies in the East of the province, and three independent endemic cycles of sylvatic rabies spread throughout the province. Furthermore, evidence of specific events of virus spill-over between co-habiting sylvatic species and domestic dogs was found. These results suggest that the elimination of canine-mediated rabies from the province will rely not only on eliminating the disease from the dog populations, but also from the co-habiting sylvatic populations using oral rabies vaccination campaigns.

The Successful Elimination of Sylvatic Rabies Using Oral Vaccination of Foxes in Slovenia.

Sylvatic rabies was present in Slovenia between 1973 and 2013, with the red fox as the main reservoir of the rabies virus. The first oral rabies vaccination (ORV) control program in foxes started in 1988, using the manual distribution of baits. Significant improvement of fox vaccination was achieved with the aerial distribution of baits, starting in 1995 and successfully finished with the final, fifty-ninth vaccination campaign in 2019. Between 1979 and 2019, a total of 86,471 samples were tested, and 10,975 (12.69%) rabies-positive animals were identified. Within the ORV, two different vaccines were used, containing modified live virus strain Street Alabama Dufferin (SAD) B19 and SAD Bern, while the last ORV campaigns were completed in 2019, with a vaccine containing a genetically modified strain of SPBN GASGAS. Molecular epidemiological studies of 95 rabies-positive samples, originating from red foxes, badgers, cattle, dogs, martens, cats, and horses, revealed a low genetic diversity of circulating strains and high similarity to strains from neighboring countries. During the elimination program, few vaccine-induced rabies cases were detected: three in red foxes and one case in a marten, with no epidemiological relevance. Slovenia has been officially declared a country free of rabies since 2016.

Local rabies transmission and regional spatial coupling in European foxes.

Infectious diseases are often transmitted through local interactions. Yet, both surveillance and control measures are implemented within administrative units. Capturing local transmission processes and spatial coupling between regions from aggregate level data is therefore a technical challenge that can shed light on both theoretical questions and practical decisions. Fox rabies has been eliminated from much of Europe through oral rabies vaccination (ORV) programmes. The European Union (EU) co-finances ORV to maintain rabies freedom in EU member and border states via a cordon sanitaire. Models to capture local transmission dynamics and spatial coupling have immediate application to the planning of these ORV campaigns and to other parts of the world considering oral vaccination. We fitted a hierarchical Bayesian state-space model to data on three decades of fox rabies cases and ORV campaigns from Eastern Germany. Specifically, we find that (i) combining regional spatial coupling and heterogeneous local transmission allows us to capture regional rabies dynamics; (ii) incursions from other regions account for less than 1% of cases, but allow for re-emergence of disease; (iii) herd immunity achieved through bi-annual vaccination campaigns is short-lived due to population turnover. Together, these findings highlight the need for regular and sustained vaccination efforts and our modelling approach can be used to provide strategic guidance for ORV delivery. Moreover, we show that biological understanding can be gained from inference from partially observed data on wildlife disease.

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

BackgroundIn 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.ResultsWhen 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%).ConclusionsThis 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.

An Analysis of Rabies Incidence and Its Geographic Spread in the Buffer Area Among Orally Vaccinated Wildlife in Ukraine From 2012 to 2016.

The statistics of rabies cases in Volyn, Lviv, and Zakarpattia oblasts of Ukraine from 2012 to 2016 were analyzed to establish spatial–temporal distribution of rabies endemic outbreaks and to identify causes of widespread infections among wild and domestic animals. The occurrence of rabies outbreaks in wild and domestic animals in Ukraine was also assessed to determine the effectiveness of oral rabies vaccination (ORV) efforts. According to our analysis, parenteral vaccination of domestic animals and ORV campaigns in foxes have proved unsuccessful in providing a sustainable, long-term reduction in endemic rabies outbreaks. ORV campaigns in foxes were deemed ineffective based on our studies of the endemic rabies outbreaks in Volyn, Lviv, and Zakarpattia oblasts in 2012–2016. The current rabies prevention system (parenteral vaccination) failed to offer protection to domestic animals based on our review of the occurrence of endemic rabies outbreaks in dogs and cats. ORV campaign shortcomings and their causes must be identified in order to provide maximum rabies vaccine coverage for dogs and cats. Altogether, the results presented here provide information that can assist public health agencies to devise more effective disease control plans to curtail the spread of rabies in domestic animals and wildlife in Ukraine.

Efficacy of oral rabies vaccination in individual age groups of juvenile red foxes

Although juvenile red foxes (Vulpes vulpes) are considered a single age group, essential for monitoring the effectiveness of the oral rabies vaccination (ORV), there appear to be significant differences among age subgroups. Herein, a subset of 335 foxes aged 0–1 year that had not consumed bait in previous campaign were collected for monitoring the effectiveness of the first seven ORV campaigns in Greece, carried out from 2013 to 2017. These juveniles were additionally assigned to three individual 4-month age groups, according to the exact date on which they were killed. The aim was to identify differences in seroconversion rate and bait uptake level and determine whether reconsideration is needed in the way that ORV monitoring is being implemented and evaluated. Statistically significant differences were observed following the analysis of mandible bone, teeth and blood samples obtained from 1–4 and 5–8-month old foxes as compared to the respective samples derived from 9–12-month old animals, whereas no differences were revealed in samples between foxes aged 1–4 and 5–8 months. Hunting juveniles during the whole period of spring ORV campaigns monitoring should be reevaluated and even discouraged. On the contrary, juvenile foxes hunted for the evaluation of autumn campaigns, aged > 8 months, had similar assessment rates to adult individuals and are equally helpful for assessing the efficacy of an ORV campaign. Taking the above into consideration and by distinguishing recent and old tetracycline uptake, ORV monitoring and evaluation could be performed in an alternative, more comprehensive way.

Rabies control in Europe: an overview of past, current and future strategies.

Europe's step-by-step approach to tackling canine and wildlife-mediated rabies has proven that the disease can be controlled and eliminated at the animal source. A decade of development work and support by the European Union has resulted in a successful oral rabies vaccination campaign for foxes and raccoon dogs, and provided the blueprint for eliminating wildlife-mediated rabies. In this paper, the authors examine the historical stages of animal rabies control and its eventual elimination in parts of Europe, particularly Western Europe. In addition, they consider current control measures and predict future challenges, many of which are faced by the vast and sparsely populated, rabies-endemic areas of Eastern Europe.

First four Oral Rabies Vaccination campaigns of the red foxes in Greece: Evaluating factors and assessment

Following the last animal rabies outbreak in Greece in 2012, Oral Rabies Vaccination (ORV) campaigns of red foxes (Vulpes vulpes) were conducted in order to halt the spread of the disease, as widely and effectively have also been implemented in other countries. The present study aims to report the main outcomes following the first Greek ORV campaigns during autumn 2013, 2014, 2015 and spring 2016, to assess their effectiveness and to investigate factors potentially related to their success. Blood samples, mandible bones and teeth, derived by 452 foxes, were tested for rabies antibody titration, animal age determination and tetracycline (TTC) detection. The laboratory results obtained were statistically analyzed. High seroprevalence and TTC detection rates were obtained following the autumn campaigns studied, while these rates were significantly reduced following the spring campaign. The year or the season of the vaccination campaign, the estimated age group of the animal and the geographical Regional Unit (RU), where the animal was hunted, were identified as important factors. On the contrary, no significance could be ascertained for TTC detection based on exclusively previous uptake, use of filter paper, blood sample type and quality, as well as sex of animal. Based on the monitoring results achieved, the first ORV campaigns conducted in the country can be generally considered to be satisfactory. No positives cases were detected since May 2014. Seasonal, geographical parameters and factors related to fox ecology may interfere with monitoring results and should be always considered when planning future ORV programs.

The economic implications of sylvatic rabies eradication in Italy.

After more than 10years of absence, sylvatic rabies re-appeared in Italy in 2008. To prevent disease spread, three oral rabies vaccination (ORV) campaigns targeting red foxes were performed through manual distribution of vaccine baits between January and September 2009. As these campaigns proved unsuccessful, at the end of December 2009, baits started being distributed using helicopters, allowing uniform coverage of larger areas in a shorter time period. From winter 2009 to autumn 2016, a total of 15 ORV campaigns (four emergency, four regular and seven preventive ORV) were implemented through aerial distribution of baits. In this study, we assessed the costs of the aerial ORV campaigns, which were aimed at eradicating the disease and reobtaining the rabies-free status. Cumulative costs per km2 were estimated at €59.45 during emergency campaigns and ranged between €51.94 and €65.67 in the regular vaccinations. The main portion of costs for ORV programmes were related to baits supply and distribution: €49.24 (82.83%) in emergency campaigns and from €40.33 to € 43.35 in regular ORVs (71.97% and 66.02%, respectively). At the end of each ORV campaign, the efficacy of vaccination activities was estimated by assessing the proportion of foxes testing positive for tetracycline biomarker in jawbone, indicating bait intake. Results revealed that the proportion of foxes that ingested baits varied between 70.97% and 95.51%. Statistical analysis indicated that reducing the density of dropped baits could potentially lead to a cost-saving of 22.81%, still maintaining a satisfactory level of bait intake by the fox population.

Preparing for and responding to recent incursions of raccoon rabies variant into Canada.

By the late 2000s, Canada had successfully eliminated the incursion of racoon rabies from the south and remained free of this rabies variant from approximately 2009 to 2014. However, new incursions of raccoon rabies variant have recently been detected in three Canadian provinces: Ontario, Quebec and New Brunswick. Actions to address previous and current incursions of this rabies variant include enhanced surveillance programs, a point infection control strategy to respond to cases, a trap-vaccine-release program and oral rabies vaccination campaigns in targeted areas to prevent further cases and spread. It is hard to predict when and where new incursions will appear because of the ecological adaptability of raccoons and the significant risk associated with inadvertent translocation events by vehicles, trains and ships and raccoon movements across bridges. To date, no cases of raccoon rabies variant have been detected in domestic animals in Canada. However, until racoon rabies can be pushed back from the Canadian border, it is important to remain prepared for the reappearance of this disease.

Rabies in the Baltic States: Decoding a Process of Control and Elimination.

Rabies is a fatal zoonosis that still causes nearly 70, 000 human deaths every year. In Europe, the oral rabies vaccination (ORV) of red foxes (Vulpes vulpes) was developed in the late 1970s and has demonstrated its effectiveness in the eradication of the disease in Western and some Central European countries. Following the accession of the three Baltic countries—Estonia, Latvia and Lithuania—to the European Union in 2004, subsequent financial support has allowed the implementation of regular ORV campaigns since 2005–2006. This paper reviews ten years of surveillance efforts and ORV campaigns in these countries resulting in the near eradication of the disease. The various factors that may have influenced the results of vaccination monitoring were assessed using generalized linear models (GLMs) on bait uptake and on herd immunity. As shown in previous studies, juveniles had lower bait uptake level than adults. For the first time, raccoon dogs (Nyctereutes procyonoides) were shown to have significantly lower bait uptake proportion compared with red foxes. This result suggests potentially altered ORV effectiveness in this invasive species compared to the red foxes. An extensive phylogenetic analysis demonstrated that the North-East European (NEE) rabies phylogroup is endemic in all three Baltic countries. Although successive oral vaccination campaigns have substantially reduced the number of detected rabies cases, sporadic detection of the C lineage (European part of Russian phylogroup) underlines the risk of reintroduction via westward spread from bordering countries. Vaccine induced cases were also reported for the first time in non-target species (Martes martes and Meles meles).

Evaluation of the first oral rabies vaccination campaign of the red foxes in Greece

Following the late 2012 recurrence of rabies in wild foxes (Vulpes vulpes) in central and north-western Greece, the first oral fox vaccination campaign co-financed by the European Union (EU) and the Greek state budget, was implemented. Initially, it involved 24 regional units of the Greek territory during the period October–December 2013. Vaccine-baits were aerially distributed by fixed-wing aircrafts. Vaccines were scattered along parallel flight paths 500m apart in order to optimize aerial missions and achieve homogeneous distribution. A geographical information system was used to objectively evaluate bait distribution. This system identified areas of inadequate bait density that would require additional flights. A total number of 1,504,821 baits were distributed covering an area of 54,584.29km2. To assess the effectiveness of oral vaccination campaign a monitoring program was introduced, which entailed examination of serum samples and canine teeth derived from red foxes collected in the field. The laboratory analysis revealed 60% seropositivity and detection of tetracycline biomarker in 70% of the foxes tested.

Implementation and monitoring of oral rabies vaccination of foxes in Kosovo between 2010 and 2013—An international and intersectorial effort

The European Union has used instrument for pre-accession (IPA) funds to provide technical assistance and supplies for the eradication, monitoring and control of rabies in several pre-accession countries. As a result, since 2010, multi-annual oral rabies vaccination (ORV) programmes for eliminating fox rabies have been launched in six Western Balkan countries.Here the implementation of the ORV programme in Kosovo, the smallest of the West Balkan countries, is described. Associated challenges under difficult political conditions, potential biases, and the results of rabies surveillance and monitoring of ORV campaigns (bait uptake and immunisation rates) since 2010 are reported.

Safety and immunogenicity of Ontario Rabies Vaccine Bait (ONRAB) in the first us field trial in raccoons (Procyon lotor).

In 2011, we conducted a field trial in rural West Virginia, USA to evaluate the safety and immunogenicity of a live, recombinant human adenovirus (AdRG1.3) rabies virus glycoprotein vaccine (Ontario Rabies Vaccine Bait; ONRAB) in wild raccoons (Procyon lotor) and striped skunks (Mephitis mephitis). We selected ONRAB for evaluation because of its effectiveness in raccoon rabies management in Ontario and Quebec, Canada, and significantly higher antibody prevalence rates in raccoons compared with a recombinant vaccinia-rabies glycoprotein (V-RG) vaccine, Raboral V-RG®, in US-Canada border studies. Raccoon rabies was enzootic and oral rabies vaccination (ORV) had never been used in the study area. We distributed 79,027 ONRAB baits at 75 baits/km(2) mostly by fixed-wing aircraft along parallel flight lines at 750-m intervals. Antibody prevalence was significantly higher at 49.2% (n=262) in raccoons after ONRAB was distributed than the 9.6% (n=395) before ORV. This was the highest antibody prevalence observed in raccoons by US Department of Agriculture Wildlife Services for areas with similar management histories evaluated before and after an initial ORV campaign at 75 baits/km(2) with Raboral V-RG. Tetracycline biomarker (TTCC) was significantly higher among antibody-positive raccoons after ONRAB baiting and was similar among raccoons before ORV had been conducted, an indication of vaccine-induced rabies virus-neutralizing antibody production following consumption of bait containing TTCC. Skunk sample size was inadequate to assess ONRAB effects. Safety and immunogenicity results supported replication of this field trial and led to a recommendation for expanded field trials in 2012 to evaluate safety and immunogenicity of ground-distributed ONRAB at 150 baits/km(2) in residential and commercial habitats in Ohio, USA and aerially distributed ONRAB at 75 baits/km(2) in rural habitats along US-Quebec border.

2008–2011 sylvatic rabies epidemic in Italy: challenges and experiences

After more than 10 years of absence, in 2008 rabies re-emerged and spread in wild foxes in north-eastern Italy. In order to control the infection and to minimize the risk of human exposure, three oral foxes vaccination campaigns were first carried out by manual distribution of baits between January and September 2009, followed by four emergency oral rabies vaccination (ORV) campaigns by aerial distribution in the affected regions starting in December 2009. Ordinary aerial ORV campaigns followed in spring and fall 2011 and 2012, although no cases were reported after February 2011. In our paper, we describe the main characteristics of the rabies epidemic that occurred in north-eastern Italy in 2008–2011, with particular focus on the innovative systems that were implemented to manage and evaluate the efficacy of the aerial ORV. The Italian experience in containing and eliminating rabies in less than 3 years may provide information and suggestions for countries affected by rabies, and sharing a similar geomorphological conformation as Italy.

The elimination of fox rabies from Europe: determinants of success and lessons for the future

Despite perceived challenges to controlling an infectious disease in wildlife, oral rabies vaccination (ORV) of foxes has proved a remarkably successful tool and a prime example of a sophisticated strategy to eliminate disease from wildlife reservoirs. During the past three decades, the implementation of ORV programmes in 24 countries has led to the elimination of fox-mediated rabies from vast areas of Western and Central Europe. In this study, we evaluated the efficiency of 22 European ORV programmes between 1978 and 2010. During this period an area of almost 1.9 million km² was targeted at least once with vaccine baits, with control taking between 5 and 26 years depending upon the country. We examined factors influencing effort required both to control and eliminate fox rabies as well as cost-related issues of these programmes. The proportion of land area ever affected by rabies and an index capturing the size and overlap of successive ORV campaigns were identified as factors having statistically significant effects on the number of campaigns required to both control and eliminate rabies. Repeat comprehensive campaigns that are wholly overlapping much more rapidly eliminate infection and are less costly in the long term. Disproportionally greater effort is required in the final phase of an ORV programme, with a median of 11 additional campaigns required to eliminate disease once incidence has been reduced by 90 per cent. If successive ORV campaigns span the entire affected area, rabies will be eliminated more rapidly than if campaigns are implemented in a less comprehensive manner, therefore reducing ORV expenditure in the longer term. These findings should help improve the planning and implementation of ORV programmes, and facilitate future decision-making by veterinary authorities and policy-makers.

ORAL RABIES VACCINATION OF RACCOONS AND STRIPED SKUNKS WITH ONRAB® BAITS: MULTIPLE FACTORS INFLUENCE FIELD IMMUNOGENICITY

Multiple control methods have been used in North America to manage the spread of rabies caused by the raccoon (Procyon lotor) rabies virus variant (RRVV). Recently, oral vaccination with ONRAB(®) vaccine baits, which contain an adenovirus rabies glycoprotein recombinant, has been made available as an additional tool for rabies control. Our objectives were to estimate rabies antibody prevalence in wild-caught raccoons and striped skunks (Mephitis mephitis), and identify factors influencing the probability of being antibody positive at the individual level in these species, following oral rabies vaccination (ORV) campaigns in which ONRAB was distributed aerially in 2007-2009 in southern Québec, Canada. Following the aerial distribution of 43-155 ONRAB baits/km(2), the annual percentages of antibody-positive raccoons and skunks varied between 35% and 56% and 11% and 17%, respectively. In raccoons, the probability of being antibody positive was positively associated with age and density of ONRAB distributed, and influenced by the number of previous ORV campaigns conducted. Conversely, this probability was negatively associated with estimated abundance of raccoons in the trapping cell and proportion of residential areas near the raccoon capture location. None of the variables examined explained variation in the probability of being antibody positive in skunks. Our results indicate that the ONRAB density applied during ORV campaigns should be adjusted to account for variations in raccoon population density and presence of residential areas to increase the likelihood of creating an effective immunological barrier against RRVV. The high percentage of juvenile raccoons (annual mean =45 ± 3 [SE]%) and skunks (66 ± 2%) captured during post-ORV monitoring suggests that ORV campaigns should be conducted at least annually to account for the recruitment of naïve individuals into the populations. In Québec, the increasing use of ONRAB coincided with the elimination of rabies caused by RRVV. Nonetheless, our results indicate that improvements to this vaccine bait and/or the distribution techniques are required to increase its efficacy, especially in striped skunks.

FIRST EUROPEAN INTERLABORATORY COMPARISON OF TETRACYCLINE AND AGE DETERMINATION WITH RED FOX TEETH FOLLOWING ORAL RABIES VACCINATION PROGRAMS

The first European interlaboratory comparison of tetracycline and age determination with red fox (Vulpes vulpes) tooth samples was organized by the European Union Reference Laboratory for rabies. Performance and procedures implemented by member states were compared. These techniques are widely used to monitor bait uptake in European oral rabies vaccination campaigns. A panel of five red fox half-mandibles comprising one weak positive juvenile sample, two positive adult samples, one negative juvenile sample, and one negative adult sample were sent, along with a technical questionnaire, to 12 laboratories participating on a voluntary basis. The results of only three laboratories (25%) were 100% correct. False-negative results were more frequently seen in weak positive juvenile samples (58%) but were infrequent in positive adult samples (4%), probably due to differences in the ease of reading the two groups of teeth. Four laboratories (44%) had correct results for age determination on all samples. Ages were incorrectly identified in both adult and juvenile samples, with 11 and 17% of discordant results, respectively. Analysis of the technical questionnaires in parallel with test results suggested that all laboratories cutting mandible sections between the canine and first premolar obtained false results. All the laboratories using longitudinal rather than transverse sections and those not using a mounting medium also produced false results. Section thickness appeared to affect the results; no mistakes were found in laboratories using sections <150 μm thick. Factors having a potential impact on the success of laboratories were discussed, and recommendations proposed. Such interlaboratory trials underline the importance of using standardized procedures for biomarker detection in oral rabies vaccination campaigns. Several changes can be made to improve analysis quality and increase the comparability of bait uptake frequencies among member states.

Serological methods used for rabies post vaccination surveys: An analysis

The assessment of fox immunity following oral rabies vaccination (ORV) is commonly applied to assess the efficacy of an ORV campaign in the field. Several ELISA kits have been developed and validated for their use for rabies serology in wildlife as an alternative to neutralizing techniques (NT), such as the fluorescent antibody virus neutralization test (FAVN) and the rapid fluorescent foci inhibition test (RFFIT). At a European level, NT and ELISA tests are used interchangeably and on different types of samples collected for vaccination follow-up. This has resulted in a difficulty in comparing the results generated with different diagnostic tools. We have evaluated (a) the effect of two different matrices commonly used for serology in red foxes on the results of the FAVN and (b) the performance of two commercially available ELISAs in comparison with the FAVN, as a gold standard, using a panel of over 700 field fox samples. Moderate agreement was observed when comparing results from different matrices. We found a very low level of agreement and low values of relative sensitivity and specificity of the ELISAs tested in comparison with the FAVN. Our findings confirm, using a vast collection of field samples obtained during post-vaccination surveillance campaigns in Italy, the need for improved reliability of certain serological tests.