Divergent Rabies Virus Variant of Probable Bat Origin in 2 Gray Foxes,New Mexico,USA

In the Western Hemisphere, bat-associated rabies viruses (RABVs) have established independent transmission cycles in multiple mammal hosts, forming genetically distinct lineages. In New Mexico, USA, skunks, bats, and gray foxes are rabies reservoir hosts and represent a public health risk because of encounters with humans. During 2015 and 2019, two previously undescribed RABVs were detected in 2 gray foxes (Urocyon cinereoargenteus) in Lincoln County, New Mexico. Phylogenetic analysis of the nucleoprotein gene indicated that the isolates are a novel RABV variant. These 2 cases probably represent repeated spillover events from an unknown bat reservoir to gray foxes. Molecular analysis of rabies cases across New Mexico identified that other cross-species transmission events were the result of viral variants previously known to be enzootic to New Mexico. Despite a robust rabies public health surveillance system in the United States, advances in testing and surveillance techniques continue to identify previously unrecognized zoonotic pathogens.     

Elimination of arctic variant rabies in red foxes, metropolitan Toronto

To control the Arctic variant of rabies virus in red foxes, 332,257 bait doses containing live, attenuated Evelyn-Rokitnicki-Abelseth rabies vaccine were distributed in greater metropolitan Toronto during 1989-1999. Human and pet contact with bait was minimal, and no adverse reactions to the vaccine were noted. Significantly fewer rabid foxes were found during the 17 years after fox baiting (5 cases during 1990-2006) than in the 17 years before (96 cases during 1973-1989). The last report of a rabid fox in metropolitan Toronto was in 1996 (reporting period through September 2006), which confirms that distributing oral rabies vaccine bait is a feasible tactic for the control of rabies in foxes in urban environments.     

Oral rabies vaccination of arctic foxes (Alopex lagopus) with an attenuated vaccine.

Arctic foxes were immunized with the SAG1 oral rabies vaccine. The effectiveness was determined by the serological response and by the survival to a challenge dose of rabies virus from an Alaskan fox. Vaccine virus was isolated from saliva 1 h after the liquid vaccine was placed directly into the mouth but not subsequently (tested up to 1 week postvaccination). Two weeks after vaccination, protective antibody levels were present in all foxes and all vaccinated foxes survived challenge at 9 weeks postvaccination. At 26 weeks postvaccination (17 weeks postchallenge) all but one fox had detectable antibody levels. Neural tissue harvested from surviving foxes was negative for rabies virus by direct immunofluorescent testing. One of the foxes vaccinated with SAG1 seroconverted and survived challenge even though the titre of the vaccine used was almost 4 logs less than that used to vaccinate the other foxes. These results suggest that the avirulent SAG1 oral rabies vaccine is very effective in protecting arctic foxes.     

Molecular epidemiology of rabies in northern Colombia 1994-2003. Evidence for human and fox rabies associated with dogs

During the period 2000-2003, wild grey foxes (Urocyon cinereoargenteus) in northern Colombia became infected with rabies. In order to derive phylogenetic relationships between rabies viruses isolated in foxes, dogs and humans in this region, 902 nt cDNA fragments containing the G-L intergenic region and encoding the cytoplasmic domain of protein G and a fragment of protein L were obtained by RT-PCR, sequenced and compared. Phylogenetic analysis showed that rabies viruses isolated in foxes, dogs and humans belonged to a single genetic variant. Speculative analysis together with epidemiological data indicated that rabies in foxes may have been due to contact with rabid dogs. Rabies transmission between dogs, wild foxes and humans may happen in natural conditions in northern Colombia. This finding is the first to suggest dog-to-fox rabies transmission in South America, and provides another example of dog rabies variants being able to successfully colonize wildlife hosts.     

Oral vaccination and protection of red foxes (Vulpes vulpes) against rabies using ONRAB,an adenovirus-rabies recombinant vaccine

Twenty-seven red foxes (Vulpes vulpes) were each offered a bait containing ONRAB^®, a recombinant oral rabies vaccine that uses a human adenovirus vector to express the immunogenic rabies virus glycoprotein; 10 controls received no vaccine baits. Serum samples collected from all foxes before treatment, and each week post-treatment for 16 weeks, were tested for the presence of rabies virus neutralizing antibody (RVNA). In the bait group, a fox was considered a responder to vaccination if serum samples from 3 or more consecutive weeks had RVNA ≥0.5 IU/ml. Using this criterion, 79% of adult foxes (11/14) and 46% of juveniles (6/13) responded to vaccination with ONRAB^®. Serum RVNA of adults first tested positive (≥0.5 IU/ml) between weeks 1 and 3, about 4 weeks earlier than in juveniles. Adults also responded with higher levels of RVNA and these levels were maintained longer. Serum samples from juveniles tested positive for 1–4 consecutive weeks; in adults the range was 2–15 weeks, with almost half of adults maintaining titres above 0.5 IU/ml for 9 or more consecutive weeks. Based on the kinetics of the antibody response to ONRAB^®, the best time to sample sera of wild adult foxes for evidence of vaccination is 7–11 weeks following bait distribution. Thirty-four foxes (25 ONRAB^®, 9 controls) were challenged with vulpine street virus 547 days post-vaccination. All controls developed rabies whereas eight of 13 adult vaccinates (62%) and four of 12 juvenile vaccinates (33%) survived. All foxes classed as non-responders to vaccination developed rabies. Of foxes considered responders to vaccination, 80% of adults (8/10) and 67% of juveniles (4/6) survived challenge. The duration of immunity conferred to foxes would appear adequate for bi-annual and annual bait distribution schedules as vaccinates were challenged 1.5 years post-vaccination.     

Rabies in Canada,with special reference to wildlife reservoirs

The course of known outbreaks of rabies in Canada in the 20th century is sketched, and the present extensive enzootic described. Its spread throughout the North West Territories, and in the Provinces of Alberta, British Columbia, Manitoba, Quebec, and Saskatchewan, is attributed to the vast potential reservoirs of infection offered by the density of fauna in these areas—in particular, of foxes and wolves. Control and eradication is being attempted—with some success—chiefly by reducing the wildlife population and restricting the movement of dogs.     

Emergence of dog rabies in the northern region of Israel

Between 1979 and 2000, foxes constituted the main reservoir of rabies in the Northern regions of Israel. Following the implementation of the fox-targeted oral vaccination programme (ORV) in 1998, rabies was eradicated from this area. Subsequently during 2004-2007, the biological and molecular characterization of the rabies isolates showed that stray dogs emerged as the main animal reservoir in Northern Israel while lower numbers of cases were reported in domestic animals. The virus isolates from foxes and dogs differed, in their molecular characterization, suggesting two distinct separate lineages. The transition from fox-mediated rabies to dog-mediated rabies is of great concern to public health because of the close contact between dogs and the human population.     

Update: raccoon rabies epizootic--United States and Canada, 1999

In 1977, an outbreak of raccoon rabies was detected in an area on the West Virginia-Virginia border. Since then, the area affected by this distinct variant of rabies virus associated with raccoons has spread to Ohio in the west and New York, Pennsylvania, Vermont, New Hampshire, and Maine in the north. In addition, the once separate epizootics of rabies among raccoons in the southeastern and mid-Atlantic states converged in North Carolina. In July 1999, the raccoon rabies virus variant was reported from Ontario, Canada, on the New York border. This report describes the spread of this epizootic of raccoon rabies through mid-Atlantic and northeastern states and into Canada.     

Vaccine-induced rabies case in a cow (Bos taurus): Molecular characterisation of vaccine strain in brain tissue

Rabies is a fatal neuropathogenic zoonosis caused by the rabies virus of the Lyssavirus genus, Rhabdoviridae family. The oral vaccination of foxes — the main reservoir of rabies in Europe — using a live attenuated rabies virus vaccine was successfully conducted in many Western European countries. In July 2015, a rabies vaccine strain was isolated from the brain tissues of a clinically suspect cow (Bos taurus) in Romania. The nucleotide analysis of both N and G gene sequences showed 100% identity between the rabid animal, the GenBank reference SAD B19 strain and five rabies vaccine batches used for the national oral vaccination campaign targeting foxes.     

Survey of fox trappers in northern Alaska for rabies antibody.

The purpose of this research was to determine whether trappers in northern Alaska acquired immunity to rabies virus from non-bite exposures while trapping and skinning arctic foxes (Alopex lagopus). In coastal Alaska recurring epizootics presumably provide trappers ample opportunity for contact with rabid animals. Serum neutralization analyses of blood samples collected from 26 individuals were conducted. All but three had negative rabies neutralizing antibody levels (< 0.05 I.U./ml). Two of these had previously received rabies vaccine but one individual who had trapped for about 47 years with an estimated harvest of over 3000 foxes and who had never received pre- or post-exposure rabies vaccination had a rabies serum neutralizing antibody concentration of 2.30 I.U./ml. This represents the first report of an unvaccinated person acquiring rabies virus antibody with a titre above the 0.5 I.U./ml level considered acceptable by the World Health Organization.     

Rabies-free status of the Czech Republic after 15 years of oral vaccination

Rabies in foxes was widespread in the Czech Republic after World War II, reaching its highest incidence in the 1980s. Applied control measures had only a limited effect and rabies incidence in wildlife continuously endangered both domestic animals and human beings. A significant improvement was noticed after the introduction of oral vaccination of foxes in 1989. The original manual distribution of vaccine baits has been replaced by aerial distribution, leading to the total elimination of rabies throughout the country. The last case of rabies was diagnosed in a fox in the district of Trutnov in April 2002. Since that time no case of rabies has been registered in the Czech Republic, and it therefore fulfils the requirements for the status of a 'rabies-free country'. Effective epidemiological surveillance and preventive oral vaccination of foxes will be necessary to maintain this status, especially in the endangered border regions.     

Serological data on rabies in foxes studied in Iran]

During the epidemiological research of zoonoses, the authors have studied the rabies of wild animals: fox. For the serological tests, the blood was taken by heart puncture of foxes. 193 specimens were tested and 26 (13.5%) of the foxes had neutralizing antibody in their blood. This study confirms that during the rabies epizooty, the Vulpin population, may contract a non-fatal disease and produce the neutralizing antibody. Thus, the fox has a real place in the epidemiology of rabies in Iran.     

Enzootic Rabies Elimination from Dogs and Reemergence in Wild Terrestrial Carnivores, United States

To provide molecular and virologic evidence that domestic dog rabies is no longer enzootic to the United States and to identify putative relatives of dog-related rabies viruses (RVs) circulating in other carnivores, we studied RVs associated with recent and historic dog rabies enzootics worldwide. Molecular, phylogenetic, and epizootiologic evidence shows that domestic dog rabies is no longer enzootic to the United States. Nonetheless, our data suggest that independent rabies enzootics are now established in wild terrestrial carnivores (skunks in California and north-central United States, gray foxes in Texas and Arizona, and mongooses in Puerto Rico), as a consequence of different spillover events from long-term rabies enzootics associated with dogs. These preliminary results highlight the key role of dog RVs and human–dog demographics as operative factors for host shifts and disease reemergence into other important carnivore populations and highlight the need for the elimination of dog-related RVs worldwide.     

The ascension of wildlife rabies: a cause for public health concern or intervention?

The epidemiology of rabies in the United States has changed substantially during the last half century, as the source of the disease has changed from domesticated animals to wildlife, principally raccoons, skunks, foxes, and bats. Moreover, the changes observed among affected wildlife populations have not occurred without human influence. Rather, human attraction to the recreational and economic resources provided by wildlife has contributed to the reemergence of rabies as a major zoonosis. Although human deaths caused by rabies have declined recently to an average of one or two per year, the estimated costs associated with the decrease in deaths amount to hundreds of millions of dollars annually. In future efforts to control rabies harbored by free-ranging animal reservoirs, public health professionals will have to apply imaginative, safe, and cost-effective solutions to this age-old malady in addition to using traditional measures.     

The development and use of a vaccinia-rabies recombinant oral vaccine for the control of wildlife rabies; a link between Jenner and Pasteur.

To improve both safety and stability of the oral vaccines used in the field to vaccinate foxes against rabies, a recombinant vaccinia virus, which expresses the immunizing G protein of rabies virus has been developed by inserting the cDNA which codes for the immunogenic glycoprotein of rabies virus into the thymidine kinase (TK) gene of the Copenhagen strain of vaccinia virus. The efficacy of this vaccine was tested by the oral route, primarily in foxes. The immunity conferred, a minimum of 12 months in cubs and 18 months in adult animals, corresponds to the duration of the protection required for vaccination of foxes in the field. Innocuity was tested in foxes, domestic animals, and in numerous European wild animal species that could compete with the red fox for the vaccine bait. No clinical signs or lesions were observed in any of the vaccinated animals during a minimum of 28 days post vaccination. Moreover, no transmission of immunizing doses of the recombinant occurred between foxes or other species tested. To study the stability of the vaccine strain, baits containing the vaccine were placed in the field. Despite considerable variations of environmental temperatures, the vaccine remained stable for at least one month. Because bait is taken within one month, it can be assumed that most animals taking the baits are effectively vaccinated. To test the field efficacy of the recombinant vaccine, large-scale campaigns of fox vaccination were set up in a 2200 km2 region of southern Belgium, were rabies was prevalent. A dramatic decrease in the incidence of rabies was noted after the campaigns. The recombinant is presently used to control wildlife rabies in the field both in several European countries and in the United States.     

ELISA test for rabies antibody titration in orally vaccinated foxes sampled in the fields

The assessment of the efficacy of rabies oral vaccination campaigns requires the titration of specific antibodies in the target species. Unfortunately, in Continental Europe, most fox serum samples are in fact “body fluids” taken from cadavers and the lack of a validated titration method for these poor quality sera made it impossible to survey and compare the efficacy of various oral vaccination protocols used by the different European teams. By using ready to use microplates sensitised with rabies virus glycoprotein purchased from a manufacturer and applying a simple and rapid ELISA technique on field fox sera, we obtained antibody quantitation highly correlated with seroneutralising antibody titres measured with a seroneutralisation test on cell culture. We obtained, with fox sera sampled in the same area, the same distribution of high, medium and low titres within all categories of serum quality (from high to very poor quality) and therefore conclude that this ELISA test allows a reliable titration even with highly contaminated body fluids. This test was shown to be equally capable of detecting rabies antibodies in serum samples taken from foxes vaccinated with an highly attenuated rabies virus (the SAG2 double mutant of the Street Alabama Dufferin strain) or with the VRG, the Vaccinia recombinant glycoprotein. Additionally, a strong correlation was demonstrated between titres given by this ELISA (or by the seroneutralisation test) and protection against challenge of foxes orally vaccinated with SAG2 vaccine baits. In view of this validation, this simple and reliable test is proposed for sero-surveying foxes following rabies oral vaccination campaigns.     

Sarcoptic mange in Swedish wildlife.

Mange caused by Sarcoptes scabiei var. vulpes appeared among red foxes (Vulpes vulpes) in Scandinavia (south-west Finland) for the first time in this century in 1967. The disease was most probably introduced by foxes crossing the Gulf of Finland from Estonia. The mange epizootic spread northwards through Finland and reached Sweden in late 1975, when mangy foxes appeared in the northern part of the country. In 1984, mange was observed in most parts of Sweden. The disease was observed to spread rapidly in boreal areas, whereas it spread more slowly in agricultural areas. Mortality due to mange was very high. The duration of the disease before death due to emaciation has been shown experimentally to be over 90 days. An outbreak of fox mange among Arctic foxes (Alopex lagopus) occurred in 1986. The local population of Arctic foxes was caught and successfully treated. The following year, treated foxes were caught again and no signs of disease were found. Sporadic cases of fox mange have also been diagnosed in lynx (Lynx lynx), pine marten (Martes martes) and domestic dogs. Single cases have been observed in other species: wolf (Canis lupus), mountain hare (Lepus timidus), domestic cat and horse. No cases of sarcoptic mange have been recorded in the badger (Meles meles). At present, although fox mange occurs as an epizootic in local populations, the number of foxes has increased again in many parts of Sweden.     

Rabies immunization of red foxes (Vulpes fulva) with vaccine in sausage baits.

Foxes were orally vaccinated against rabies with two modified live vaccine viruses, ERA/BHK-21 and PRI strain, in sausage baits. The baits proved acceptable to caged foxes and effectively delivered immunizing doses of vaccine. Antibody profiles on the vaccinated foxes and intramuscular challenge with "street" rabies virus showed the ERA/BHK-21 vaccine to be more effective than the PRI vaccine. The addition of a stabilizer helped maintain virus titers when the baits were subjected to high (35 C) temperature.     

Efficacy of the oral rabies virus vaccine strain SPBN GASGAS in foxes and raccoon dogs

To test the immunogenicity and efficacy of a new oral rabies virus vaccine strain SPBN GASGAS in wildlife target species, one group of foxes and two groups of raccoon dogs were offered a bait containing 1.7 ml of the vaccine (10^6.6 FFU/ml; 10^6.8 FFU/dose) and subsequently challenged approximately 180 days later with a fox rabies virus isolate. One group of raccoon dogs (n = 30) received the same challenge dose (10^0.7 MICLD₅₀/ml) as the red foxes (n = 29). The other group with raccoon dogs (n = 28) together with 8 animals that received the vaccine dose by direct instillation into the oral cavity (DIOC) were infected with a 40-fold higher dose of the challenge virus (10^2.3 MICLD₅₀/ml). All but one of the 29 vaccinated foxes survived the challenge infection; meanwhile all 12 control foxes succumbed to rabies. Twenty-eight of 30 vaccinated raccoon dogs challenged with the same dose survived the infection, however only six of 12 control animals succumbed. When the higher challenge dose was administered, all 12 control animals died from rabies and all 36 vaccinated animals (28 baited plus 8 DIOC) survived. Blood samples were collected at different time points post vaccination and examined by both RFFIT and ELISA. The kinetics of the measured immune response was similar for both species, although in RFFIT slightly higher values were observed in foxes than in raccoon dogs. However, the immune response as measured in ELISA was identical for both species. The oral rabies virus vaccine SPBN GASGAS meets the efficacy requirements for live rabies virus vaccines as laid down by the European Pharmacopoeia.     

Molecular Epidemiology of Reemergent Rabies in Yunnan Province,Southwestern China

Yunnan Province in China borders 3 countries (Vietnam, Laos, and Myanmar) in Southeast Asia. In the 1980s, a large-scale rabies epidemic occurred in this province, which subsided by the late 1990s. However, 3 human cases of rabies in 2000 indicated reemergence of the disease in 1 county. In 2012, rabies was detected in 77 counties; 663 persons died of rabies during this new epidemic. Fifty two rabies virus strains obtained during 2008–2012 were identified and analyzed phylogenetically by sequencing the nucleoprotein gene. Of the 4 clades identified, clades YN-A and YN-C were closely related to strains from neighboring provinces, and clade YN-B was closely related to strains from Southeast Asia, but formed a distinct branch. Rabies virus diversity might be attributed to dog movements among counties, provinces, and neighboring countries. These findings suggest that Yunnan Province is a focal point for spread of rabies between Southeast Asia and China.