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

Assessing Red Fox (Vulpes vulpes) Demographics to Monitor Wildlife Diseases: A Spotlight on Echinococcus multilocularis

The assessment of red fox population density is considered relevant to the surveillance of zoonotic agents vectored by this species. However, density is difficult to estimate reliably, since the ecological plasticity and elusive behavior of this carnivore hinder classic methods of inference. In this study, red fox population density was estimated using a non-invasive molecular spatial capture-recapture (SCR) approach in two study areas: one in a known hotspot of the zoonotic cestode Echinococcus multilocularis, and another naïve to the parasite. Parasitological investigations on collected samples confirmed the presence of the parasite exclusively in the former area; the SCR results indicated a higher fox population density in the control area than in the hotspot, suggesting either that the relationship between fox density and parasite prevalence is not linear and/or the existence of other latent factors supporting the parasitic cycle in the known focus. In addition, fox spotlight count data for the two study areas were used to estimate the index of kilometric abundance (IKA). Although this method is cheaper and less time-consuming than SCR, IKA values were the highest in the areas with the lower molecular SCR density estimates, confirming that IKA should be regarded as a relative index only.

Wolf Dispersal Patterns in the Italian Alps and Implications for Wildlife Diseases Spreading

Simple Summary

Wildlife dispersal directly influences population expansion patterns, and may have indirect effects on the spread of wildlife diseases. For many species, little is known about dispersal, despite its importance to conservation. We documented the natural dispersal processes of an expanding wolf (Canis lupus) population in the Italian Alps to understand the dynamics of the recolonization pattern and identify diseases that might be connected with the process through the use of non-invasive genetic sampling over a 20-year period. By documenting 55 dispersal events, with an average minimum straight dispersal distance of 65.8 km (±67.7 km), from 7.7 km to 517.2 km, we discussed the potential implications for maintaining genetic diversity of the population and for wildlife diseases spreading.

Abstract

Wildlife dispersal directly influences population expansion patterns, and may have indirect effects on the spread of wildlife diseases. Despite its importance to conservation, little is known about dispersal for several species. Dispersal processes in expanding wolf (Canis lupus) populations in Europe is not well documented. Documenting the natural dispersal pattern of the expanding wolf population in the Alps might help understanding the overall population dynamics and identifying diseases that might be connected with the process. We documented 55 natural dispersal events of the expanding Italian wolf alpine population over a 20-year period through the use of non-invasive genetic sampling. We examined a 16-locus microsatellite DNA dataset of 2857 wolf samples mainly collected in the Western Alps. From this, we identified 915 individuals, recaptured 387 (42.3%) of individuals, documenting 55 dispersal events. On average, the minimum straight dispersal distance was 65.8 km (±67.7 km), from 7.7 km to 517.2 km. We discussed the potential implications for maintaining genetic diversity of the population and for wildlife diseases spreading.

Rabies in Europe: An epidemiological and clinical update

Rabies is a vaccine preventable zoonotic disease with a significant mortality burden worldwide. Several years of vaccination campaigns in wildlife animals have now achieved the control of rabies in Western Europe through a vaccination belt in front of endemic Eastern European countries. Nevertheless, rabies could be imported both by travellers from areas without an active public control of the disease or by animals coming from areas where the virus circulates in wildlife fauna. The knowledge of the current world epidemiology combined with a high index of clinical suspicion are needed to reach a diagnosis of rabies, especially in case of atypical presentation or without a history of animal exposure. The pre-travel counselling to people visiting highly endemic areas is essential to give information on how to reduce exposure to potential sources of infection and to select those subjects who could benefit from pre-travel vaccination. Rabies is almost invariably fatal, but the prompt administration of a vaccine course combined with anti-rabies immunoglobulins significantly reduces the probability to develop life-threatening consequences. In this review, we give a brief epidemiological and clinical update about rabies in Europe.

Analysis of seroprevalence in target wildlife during the oral rabies vaccination programme in Lithuania

BACKGROUND

Rabies vaccination of wildlife carnivores is a powerful tool to prevent, control and eliminate rabies. The presence of neutralizing rabies antibodies in blood is considered a reliable indicator of adequate vaccination. The main purpose of the present study was to analyze the seroprevalence of specific antibodies in target populations of Lithuanian red fox (RF) and raccoon dog (RD) during the oral rabies vaccination (ORV) campaigns during the 2010-2019 period.

RESULTS

Over the ten-year period, 7,261 RF and 2,146 RD sera samples were collected post-mortem in field conditions and tested using a commercial standardized enzyme-linked immunosorbent assay (ELISA) kit in Lithuania. In the ORV spring and autumn vaccination periods, 31.8% (20.3-43.4 95% CI - 95% confidence interval) and 31.7% (21.2-42.1 95% CI) of RF, and 34.1% (22.5-45.7 95% CI) and 34.7% (22.7-46.7 95% CI) of RD sera samples, respectively, were identified as ELISA-positive (seroconversion ≥ 0.5 EU/mL-Equivalent Units per Millilitre). The seroprevalence analysis in adult/ juvenile animal subpopulations indicated that 34.9% (27.2-42.5 95% CI) and 29.2% (20.3-37.9 95% CI) of RF, and 35.6% (25.2-46.0 95% CI) and 30.6% (20.2-40.9 95% CI) of RD sera samples, respectively, were identified as ELISA-positive (seroconversion ≥ 0.5 EU/mL). Statistically strong determinate correlations (r) between the serological results (pos.%) in RF adult/juvenile animal subpopulations (r = 0.937) and between RF and RD positive seroconvert (pos.%) sera samples during the spring vaccinations (r = 0.864) were demonstrated. In different ORV periods, 14-29% of RF and 7-25% of RD sera samples were identified as ELISA-negative (seroconversion < 0.5 EU/mL), but with low (0.125 < 0.49 EU/mL) antibody (Abs) titres.

CONCLUSIONS

The 2010-2019 ORV programme has been an effective tool in both RF and RD populations in Lithuania. The rabies-free status of Lithuania was self-declared in 2015 with only three rabies cases identified in buffer zones since then. The percentage of ELISA-positive serum samples (seroconversion ≥ 0.5 EU/mL) during the different periods of vaccination was similar in RF and RD populations-32% and 34% respectively. The identified seroconversion average of 21.5% in RF and 16% in RD sera samples were officially identified as ELISA-negative (seronversion < 0.5 EU/mL), but with low 0.125 < 0.49 EU/mL Abs titres. That low, but positive seroconversion participated in the formation of populations overall immune status and can influence the interpretation of oral vaccination efficacy.

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.

Echinococcus multilocularis and other cestodes in red foxes (Vulpes vulpes) of northeast Italy, 2012-2018

Background

Echinococcus multilocularis is a small tapeworm affecting wild and domestic carnivores and voles in a typical prey-predator life cycle. In Italy, there has been a focus of E. multilocularis since 1997 in the northern Italian Alps, later confirmed in red foxes collected from 2001 to 2005. In this study, we report the results of seven years of monitoring on E. multilocularis and other cestodes in foxes and describe the changes that occurred over time and among areas (eco-regions) showing different environmental and ecological features on a large scale.

Methods

Eggs of cestodes were isolated from feces of 2872 foxes with a sedimentation/filtration technique. The cestode species was determined through multiplex PCR, targeting and sequencing ND1 and 12S genes. Analyses were aimed to highlight variations among different eco-regions and trends in prevalence across the study years.

Results

Out of 2872 foxes, 217 (7.55%) samples resulted positive for cestode eggs at coproscopy, with differences of prevalence according to year, sampling area and age class. Eight species of cestodes were identified, with Taenia crassiceps (2.65%), Taenia polyacantha (1.98%) and E. multilocularis (1.04%) as the most represented. The other species, Mesocestoides litteratus, Taenia krabbei, T. serialis, T. taeniaeformis and Dipylidium caninum, accounted for < 1% altogether. Echinococcus multilocularis was identified in foxes from two out of six eco-regions, in 30 fecal samples, accounting for 1.04% within the cestode positives at coproscopy. All E. multilocularis isolates came from Bolzano province. Prevalence of cestodes, both collectively and for each of the three most represented species (T. crassiceps, T. polyacantha and E. multilocularis), varied based on the sampling year, and for E. multilocularis an apparent increasing trend across the last few years was evidenced.

Conclusions

Our study confirms the presence of a focus of E. multilocularis in red foxes of northeast Italy. Although this focus seems still spatially limited, given its persistence and apparent increasing prevalence through the years, we recommend research to be conducted in the future on the ecological factors that, on a smaller scale, allow this zoonotic species to persist. On the same scale, we recommend a health education campaign to inform on the measures to prevent this zoonosis, targeted at people living in the area, especially hunters, dog owners, forestry workers and other potentially exposed categories.

Spatiotemporal spread of sarcoptic mange in the red fox (Vulpes vulpes) in Switzerland over more than 60 years: lessons learnt from comparative analysis of multiple surveillance tools

BACKGROUND

Sarcoptic mange is a contagious skin disease of wild and domestic mammals caused by the mite Sarcoptes scabiei. Reports of sarcoptic mange in wildlife increased worldwide in the second half of the 20th century, especially since the 1990s. The aim of this study was to provide new insights into the epidemiology of mange by (i) documenting the emergence of sarcoptic mange in the red fox (Vulpes vulpes) in the last decades in Switzerland; and (ii) describing its spatiotemporal spread combining data obtained through different surveillance methods.

METHODS

Retrospective analysis of archived material together with prospective data collection delivered a large dataset from the 19th century to 2018. Methods included: (i) a review of historical literature; (ii) screening of necropsy reports from general health surveillance (1958-2018); (iii) screening of data on mange (1968-1992) collected during the sylvatic rabies eradication campaign; (iv) a questionnaire survey (<1980-2017) and (v) evaluation of camera-trap bycatch data (2005-2018).

RESULTS

Sarcoptic mange in red foxes was reported as early as 1835 in Switzerland. The first case diagnosed in the framework of the general health surveillance was in 1959. Prior to 1980, sarcoptic mange occurred in non-adjacent surveillance districts scattered all over the country. During the period of the rabies epidemic (1970s-early 1990s), the percentage of foxes tested for rabies with sarcoptic mange significantly decreased in subregions with rabies, whereas it remained high in the few rabies-free subregions. Sarcoptic mange re-emerged in the mid-1990s and continuously spread during the 2000-2010s, to finally extend to the whole country in 2017. The yearly prevalence of mange in foxes estimated by camera-trapping ranged from 0.1-12%.

CONCLUSIONS

Sarcoptic mange has likely been endemic in Switzerland as well as in other European countries at least since the mid-19th century. The rabies epidemics seem to have influenced the pattern of spread of mange in several locations, revealing an interesting example of disease interaction in free-ranging wildlife populations. The combination of multiple surveillance tools to study the long-term dynamics of sarcoptic mange in red foxes in Switzerland proved to be a successful strategy, which underlined the usefulness of questionnaire surveys.

Zero Endemic Cases of Wildlife Rabies (Classical Rabies Virus, RABV) in the European Union by 2020: An Achievable Goal

The elimination of rabies transmitted by Classical Rabies Virus (RABV) in the European Union (EU) is now in sight. Scientific advances have made it possible to develop oral vaccination for wildlife by incorporating rabies vaccines in baits for foxes. At the start of the 1980s, aerial distribution of vaccine baits was tested and found to be a promising tool. The EU identified rabies elimination as a priority, and provided considerable financial and technical resources to the infected EU Member States, allowing regular and large-scale rabies eradication programs based on aerial vaccination. The EU also provides support to non-EU countries in its eastern and south eastern borders. The key elements of the rabies eradication programs are oral rabies vaccination (ORV), quality control of vaccines and control of their distribution, rabies surveillance and monitoring of the vaccination effectiveness. EU Member States and non-EU countries with EU funded eradication programs counted on the technical support of the rabies subgroup of the Task Force for monitoring disease eradication and of the EU Reference Laboratory (EURL) for rabies. In 2018, eight rabies cases induced by classical rabies virus RABV (six in wild animals and two in domestic animals) were detected in three EU Member States, representing a sharp decrease compared to the situation in 2010, where there were more than 1500 cases in nine EU Member States. The goal is to reach zero cases in wildlife and domestic animals in the EU by 2020, a target that now seems achievable.

Resurgence of rabies in Hungary during 2013-2014: An attempt to track the origin of identified strains

In 2013-2014, accumulation of rabies episodes raised concerns regarding ongoing elimination programme in Hungary. Nearly four dozen cases were identified over a 13-month period in the central region of the country far behind the immunization zones. Although the outbreak was successfully controlled, the origin of disease remained unknown. In this study, we sequenced the partial N and G genes from 47 Hungarian rabies virus (RV) strains isolated from the 2013-2014 outbreak. Sequencing and phylogenetic analysis of the N and G genes showed that the Hungarian RV isolates share high nucleotide similarity among each other (up to 100%). When analysing the N gene, comparable sequence similarity was seen between the outbreak strains and some historic Romanian RV strains. Unfortunately, in the lack of available sequence data from the Romanian RV strains, the genetic relationship within the G gene could not be determined. Phylogenetic analysis of Hungarian RV isolates detected in the past revealed that multiple independent RV lineages circulated in our country over the past 25 years. The parental strain of the 2013-2014 outbreak may have been imported independently perhaps from east through transborder movement of a reservoir animal. Next to the introduction, this imported RV strain seems to have spread clonally in the affected area. Our findings indicate that despite effective control measures that, overall, minimized the incidence of rabies over the past decade, field and laboratory monitoring needs to be continued to make rabies elimination programme in Hungary successful.

Jet set pets: examining the zoonosis risk in animal import and travel across the European Union

Ownership of companion animals or pets is popular throughout the world. Unfortunately, such animals are susceptible to and potential reservoirs of zoonotic pathogens. Close proximity to and contact with pets can lead to human infections. The distribution of zoonotic diseases associated with companion animals such as dogs and cats is not uniform around the world, and moving animals between regions, countries, and continents carries with it the risk of relocating the pathogens they might harbor. Critical among these zoonotic diseases are rabies, echinococcosis, and leishmania. In addition, the protozoan parasites, Toxoplasma gondii and Giardia duodenalis, are also significant agents for human disease of pet origin. Considerable effort is applied to controlling movements of companion animals, particularly dogs, into the European Union. However, free movement of people and their pets within the European Union is a risk factor for the translocation of diseases and their vectors. This review considers the current distribution of some of these diseases, the risks associated with pet travel, and the controls implemented within Europe to prevent the free movement of zoonotic pathogens.