Landscape-Genetic Analysis of Population Structure in the Texas Gray Fox Oral Rabies Vaccination Zone

ABSTRACT In west-central Texas, USA, abatement efforts for the gray fox (Urocyon cinereoargenteus) rabies epizootic illustrate the difficulties inherent in large-scale management of wildlife disease. The rabies epizootic has been managed through a cooperative oral rabies vaccination program (ORV) since 1996. Millions of edible baits containing a rabies vaccine have been distributed annually in a 16-km to 24-km zone around the perimeter of the epizootic, which encompasses a geographic area >4 × 10⁵ km². The ORV program successfully halted expansion of the epizootic into metropolitan areas but has not achieved the ultimate goal of eradication. Rabies activity in gray fox continues to occur periodically outside the ORV zone, preventing ORV zone contraction and dissipation of the epizootic. We employed a landscape-genetic approach to assess gray fox population structure and dispersal in the affected area, with the aim of assisting rabies management efforts. No unique genetic clusters or population boundaries were detected. Instead, foxes were weakly structured over the entire region in an isolation by distance pattern. Local subpopulations appeared to be genetically non-independent over distances >30 km, implying that long-distance movements or dispersal may have been common in the region. We concluded that gray foxes in west-central Texas have a high potential for long-distance rabies virus trafficking. Thus, a 16-km to 24-km ORV zone may be too narrow to contain the fox rabies epizootic. Continued expansion of the ORV zone, although costly, may be critical to the long-term goal of eliminating the Texas fox rabies virus variant from the United States.     

Spatio-temporal Use of Oral Rabies Vaccines in Fox Rabies Elimination Programmes in Europe

In Europe, the elimination of wildlife rabies using oral rabies vaccination [ORV] of foxes for more than 30 years has been a success story. Since a comprehensive review on the scope of the different oral rabies vaccine baits distributed across Europe has not been available yet, we evaluated the use of different vaccine baits over the entire period of ORV [1978–2014]. Our findings provide valuable insights into the complexity of ORV programs in terms of vaccine related issues. More than 10 oral vaccines against rabies were used over the past four decades. Depending on many factors, the extent to which oral rabies virus vaccines were used varied considerably resulting in huge differences in the number of vaccine doses disseminated in ORV campaigns as well as in large spatial and temporal overlaps. Although vaccine virus strains derived from the SAD rabies virus isolate were the most widely used, the success of ORV campaigns in Europe cannot be assigned to a single oral rabies virus vaccine alone. Rather, the successful elimination of fox rabies is the result of an interaction of different key components of ORV campaigns, i.e. vaccine strain, vaccine bait and strategy of distribution.     

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.     

Elimination of rabies from red foxes in eastern Ontario

The province of Ontario (Canada) reported more laboratory confirmed rabid animals than any other state or province in Canada or the USA from 1958-91, with the exception of 1960-62. More than 95% of those cases occurred in the southern 10% of Ontario (approximately 100,000 km2), the region with the highest human population density and greatest agricultural activity. Rabies posed an expensive threat to human health and significant costs to the agricultural economy. The rabies variant originated in arctic foxes: the main vector in southern Ontario was the red fox (Vulpes vulpes), with lesser involvement of the striped skunk (Mephitis mephitis). The Ontario Ministry of Natural Resources began a 5 yr experiment in 1989 to eliminate terrestrial rabies from a approximately 30,000 km2 study area in the eastern end of southern Ontario. Baits containing oral rabies vaccine were dropped annually in the study area at a density of 20 baits/km2 from 1989-95. That continued 2 yr beyond the original 5 yr plan. The experiment was successful in eliminating the arctic fox variant of rabies from the whole area. In the 1980's, an average of 235 rabid foxes per year were reported in the study area. None have been reported since 1993. Cases of fox rabies in other species also disappeared. In 1995, the last bovine and companion animal cases were reported and in 1996 the last rabid skunk occurred. Only bat variants of rabies were present until 1999, when the raccoon variant entered from New York (USA). The success of this experiment led to an expansion of the program to all of southern Ontario in 1994. Persistence of terrestrial rabies, and ease of elimination, appeared to vary geographically, and probably over time. Ecological factors which enhance or reduce the long term survival of rabies in wild foxes are poorly understood.     

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).     

Phylogenetic relationship of street rabies virus strains and their antigenic reactivity with antibodies induced by vaccine strains. I. Analysis of phylogenetic relationship of street rabies virus strains isolated in Poland

The aims of these studies were: genetic characteristic of street rabies virus strains isolated from different animal species in Poland and determination of phylogenetic relationships to reference laboratory strains of the street rabies viruses belonging to genotype 1 and 5. The variability of rabies isolates and their phylogenetic relationship were studied by comparing the nucleotide sequence of the virus genome fragment. The Polish strains of genotype 1 belong to four phylogenetic groups (NE, CE, NEE, EE) corresponding to four variants: fox-racoon dog (F-RD); European fox 1 (F1); European fox 2 (F2) and European fox 3 (F3). On the Polish territories there are no rabies strains representing the variant dog-wolf and typical for arctic fox variant. The similarity of nucleotide and amino acid sequences of street rabies strains belonging to genotype 1 and laboratory strain CVS is very high. It is about 91% similarity at nucleotide level and 95% at amino acid level. Rabies strain CVS is similar to genotype 5 bat strains (EBL 1) only in about 69% and 74% at nucleotide and amino acid level, respectively. The genetic divergence of rabies strains circulating in Poland raised the need of permanent epidemiological and virological surveillance. The genotype and variant of isolated strains should be determined (using PCR and RLFP methods).     

Designing Programs for Eliminating Canine Rabies from Islands: Bali,Indonesia as a Case Study

Background

Canine rabies is one of the most important and feared zoonotic diseases in the world. In some regions rabies elimination is being successfully coordinated, whereas in others rabies is endemic and continues to spread to uninfected areas. As epidemics emerge, both accepted and contentious control methods are used, as questions remain over the most effective strategy to eliminate rabies. The Indonesian island of Bali was rabies-free until 2008 when an epidemic in domestic dogs began, resulting in the deaths of over 100 people. Here we analyze data from the epidemic and compare the effectiveness of control methods at eliminating rabies.

Methodology/Principal Findings

Using data from Bali, we estimated the basic reproductive number, R ₀, of rabies in dogs, to be ∼1·2, almost identical to that obtained in ten–fold less dense dog populations and suggesting rabies will not be effectively controlled by reducing dog density. We then developed a model to compare options for mass dog vaccination. Comprehensive high coverage was the single most important factor for achieving elimination, with omission of even small areas (<0.5% of the dog population) jeopardizing success. Parameterizing the model with data from the 2010 and 2011 vaccination campaigns, we show that a comprehensive high coverage campaign in 2012 would likely result in elimination, saving ∼550 human lives and ∼$15 million in prophylaxis costs over the next ten years.

Conclusions/Significance

The elimination of rabies from Bali will not be achieved through achievable reductions in dog density. To ensure elimination, concerted high coverage, repeated, mass dog vaccination campaigns are necessary and the cooperation of all regions of the island is critical. Momentum is building towards development of a strategy for the global elimination of canine rabies, and this study offers valuable new insights about the dynamics and control of this disease, with immediate practical relevance.     

Right Place,Wrong Species: A 20-Year Review of Rabies Virus Cross Species Transmission among Terrestrial Mammals in the United States

Introduction

In the continental US, four terrestrial mammalian species are reservoirs for seven antigenic rabies virus variants. Cross species transmission (CST) occurs when a rabies virus variant causes disease in non-reservoir species.

Methods

This study analyzed national surveillance data for rabies in terrestrial mammals. The CST rate was defined as: number of rabid non-reservoir animals/number of rabid reservoir animals. CST rates were analyzed for trend. Clusters of high CST rate counties were evaluated using space-time scanning statistics.

Results

The number of counties reporting a raccoon variant CST rate >1.0 increased from 75 in 1992 to 187 in 2011; counties with skunk variant CST rates >1.0 remained unchanged during the same period. As of 2011, for every rabid raccoon reported within the raccoon variant region, there were 0.73 cases of this variant reported in non-reservoir animals. Skunks were the most common non-reservoir animal reported with the raccoon rabies variant. Domestic animals were the most common non-reservoir animal diagnosed with a skunk rabies virus variant (n = 1,601). Cross species transmission rates increased fastest among domestic animals.

Conclusions

Cross species transmission of rabies virus variants into non-reservoir animals increases the risk of human exposures and threatens current advances toward rabies control. Cross species transmission in raccoon rabies enzootic regions increased dramatically during the study period. Pet owners should vaccinate their dogs and cats to ensure against CST, particularly in regions with active foci of rabies circulation. Clusters of high CST activity represent areas for further study to better understand interspecies disease transmission dynamics. Each CST event has the potential to result in a rabies virus adapted for sustained transmission in a new species; therefore further understanding of the dynamics of CST may help in early detection or prevention of the emergence of new terrestrial rabies virus variants.     

Population structure of two rabies hosts relative to the known distribution of rabies virus variants in Alaska

For pathogens that infect multiple species, the distinction between reservoir hosts and spillover hosts is often difficult. In Alaska, three variants of the arctic rabies virus exist with distinct spatial distributions. We tested the hypothesis that rabies virus variant distribution corresponds to the population structure of the primary rabies hosts in Alaska, arctic foxes (Vulpes lagopus) and red foxes (Vulpes vulpes) to possibly distinguish reservoir and spillover hosts. We used mitochondrial DNA (mtDNA) sequence and nine microsatellites to assess population structure in those two species. mtDNA structure did not correspond to rabies virus variant structure in either species. Microsatellite analyses gave varying results. Bayesian clustering found two groups of arctic foxes in the coastal tundra region, but for red foxes it identified tundra and boreal types. Spatial Bayesian clustering and spatial principal components analysis identified 3 and 4 groups of arctic foxes, respectively, closely matching the distribution of rabies virus variants in the state. Red foxes, conversely, showed eight clusters comprising two regions (boreal and tundra) with much admixture. These results run contrary to previous beliefs that arctic fox show no fine‐scale spatial population structure. While we cannot rule out that the red fox is part of the maintenance host community for rabies in Alaska, the distribution of virus variants appears to be driven primarily by the arctic fox. Therefore, we show that host population genetics can be utilized to distinguish between maintenance and spillover hosts when used in conjunction with other approaches.     

Emergency response to raccoon rabies introduction into Ontario

During 15 July to 4 October, 1999, rabies control programs were implemented with the objective being to contain the first three confirmed cases of raccoon rabies in Canada. The strategy, called point infection control (PIC) involved the use of three tactics: population reduction (PR), trap-vaccinate-release (TVR) and oral rabies vaccination with baits (ORV), to control the spread of raccoon rabies. A total of 1,202 raccoons (Procyon lotor) and 337 skunks (Mephitis mephitis) were captured and euthanized using 24,719 trap-nights in the three PR zones around the location of the three rabies cases, near Brockville, Ontario. That represented an 83% to 91% reduction in the raccoon populations in an approximate 225 km2 area around the three rabies cases. Raccoon density in the PR zones declined from 5.1-7.1/km2 to 0.6-1.1/km2 following control. All tested specimens were negative for rabies by the fluorescent antibody test (FAT). In addition, 1,759 raccoons and 377 skunks were intramuscularly vaccinated against rabies and released using 27,956 trap-nights in an approximate 485 km2 TVR zone implemented outside of the PR zones. A total of 856 cats from both PR and TVR areas were also captured, vaccinated and released. Cost for the three PIC operations was $363,000.00 Cdn or about $500.00 Cdn/km2. To further contain the outbreak, about 81,300 baits containing Raboral V-RG oral rabies vaccine were aerially distributed on 8 and 27 September 1999, to create an 8 to 15 km wide buffer zone (1,200 km2 area) of vaccinated raccoons immediately beyond the PR and TVR zones. This was the first time that V-RG was used in Canada to orally vaccinate free ranging raccoons against rabies. Baiting costs were $241,000.00 Cdn or about $200.00 Cdn/km2 including post baiting assessment costs. As of 31 August, 2000, thirty-five additional cases (38 in total) of raccoon rabies have occurred in the control and vaccination zones. This number is far below the level of rabies prevalence in USA jurisdictions where raccoon rabies was epizootic. In the future, PIC methodologies will continue to be used in Ontario to contain isolated cases of raccoon rabies.     

Molecular epidemiology of terrestrial rabies in the former Soviet Union

Fifty-five rabies virus isolates originating from different regions of the former Soviet Union (FSU) were compared with isolates originating from Eurasia, Africa, and North America according to complete or partial nucleoprotein (N) gene sequences. The FSU isolates formed five distinct groups. Group A represented viruses originating from the Arctic, which were similar to viruses from Alaska and Canada. Group B consisted of "Arctic-like" viruses, originating from the south of East Siberia and the Far East. Group C consisted of viruses circulating in the steppe and forest-steppe territories from the European part of Russia to Tuva and in Kazakhstan. These three phylogenetic groups were clearly different from the European cluster. Viruses of group D circulate near the western border of Russia. Their phylogenetic position is intermediate between group C and the European cluster. Group E consisted of viruses originating from the northwestern part of Russia and comprised a "northeastern Europe" group described earlier from the Baltic region. According to surveillance data, a specific host can be defined clearly only for group A (arctic fox; Alopex lagopus) and for the Far Eastern part of the group B distribution area (raccoon dog; Nyctereutes procyonoides). For other territories and rabies virus variants, the red fox (Vulpes vulpes) is the main virus reservoir. However, the steppe fox (Vulpes corsac), wolf (Canis lupus), and raccoon dog are also involved in virus circulation, depending on host population density. These molecular data, joined with surveillance information, demonstrate that the current fox rabies epizootic in the territory of the FSU developed independently of central and western Europe. No evidence of positive selection was found in the N genes of the isolates. In the glycoprotein gene, evidence of positive selection was strongly suggested in codons 156, 160, and 183. At these sites, no link between amino acid substitutions and phylogenetic placement or specific host species was detected.     

Trap-vaccinate-release and oral vaccination for rabies control in urban skunks, raccoons and foxes.

Two rabies control tactics, trap-vaccinate-release (T-V-R) and oral vaccination were used for the control of rabies in skunks (Mephitis mephitis), raccoons (Procyon lotor), and foxes (Vulpes vulpes) in metropolitan Toronto, Canada. Using T-V-R, a mean of 45% to 72% (95% confidence limits of 40% to 81%) of the skunks and a mean of 17% to 68% (95% confidence limits of 14% to 76%) of the raccoons in a 60 km2 area of Toronto were vaccinated against rabies between 1987 and 1991. The area has been free of skunk rabies from May 1989 to April 1992. Forty-five rabies cases were diagnosed during 1980 to 1986. In contrast, only three skunk cases have been reported since the vaccination program began in July 1987. The T-V-R area also remained rabies free during an epizootic of skunk rabies in metropolitan Toronto during 1991. Following distribution of rabies vaccine-baits throughout the ravines of metropolitan Toronto, June 1989 to December 1991, 46% to 80% of the Toronto fox population was immunized during 1989, 1990 and 1991. Only one case of fox rabies was reported in metropolitan Toronto since vaccination began, compared to 80 cases reported between 1982 and 1988. The area has been free of reported fox rabies from October 1990 to April 1992.     

Behavior, movements, and demographics of rabid raccoons in Ontario, Canada: management implications

During 1999-2003, 127 cases of raccoon variant rabies were reported in raccoons (Procyon lotor) and striped skunks (Mephitis mephitis) in Ontario, Canada. Raccoons accounted for 98% (125/127) of the reported cases with behaviors/conditions including aggression, fighting with dogs, ataxia, vocalizations, appearance of being sick, and the presence of porcupine (Erethizon dorsatum) quills. Seventy-eight percent of the rabid raccoons were adults. Juveniles were underrepresented (22%) compared with the adult/juvenile ratios found in nonrabid Ontario raccoon populations. Of the known aged raccoons, 83% were < or = 3 yr of age, and 22% of the rabid adult female raccoons had evidence of having had a litter during the year in which they were found to be rabid. The majority of rabid raccoons were reported during the fall, winter, and spring, suggesting a relationship between raccoon behavioral activities such as denning and breeding and the timing of rabies outbreaks. Multiple cases of raccoon rabies occurred at several barns, suggesting that those structures serve as focal points of rabies transmission as a result of denning activities. Movements of five rabid raccoons (range 1,564-4,143 m) were not different from movements of nonrabid raccoons in Ontario. Sixty-six percent of the rabid animals were submitted by government staff, stressing the importance of those agencies in rabies control and surveillance operations. Increased knowledge of the behaviors of rabid raccoons should assist in the development of management strategies for rabies.     

Skunk rabies in California (1992-2003)--implications for oral rabies vaccination

Skunk-variant rabies is endemic in California (United States), and the development of oral vaccines and baits to vaccinate skunks is in progress. In 2003, the California Department of Public Health (CDPH) began to quantify the impacts of skunk-variant rabies and to assess the feasibility of using oral rabies vaccination (ORV) as a containment measure. The CDPH rabies case data for skunks were spatially depicted and analyzed using a geographic information system. Statewide, rabid skunks (1992-2003) primarily occurred in seven physiographic regions: Central Coast, North Coast, North Sierra, Sacramento Valley, San Francisco Bay and Delta, San Joaquin Valley, and South Sierra. Detailed analysis of rabid skunks in San Luis Obispo (SLO) and Santa Barbara (SB) counties showed that skunk rabies was endemic in the coastal plain of SLO County between 1992 and 2000, but only became epizootic in SB County during 2002. Despite the widespread distribution of striped skunks (Mephitis mephitis) throughout most of California, the skunk rabies variant has not been found in Los Angeles County since 1979. Results imply that future ORV campaigns for skunk-variant rabies in the Pacific Coastal Plain could deter spread from SLO into SB County, as well as deterring the reintroduction of skunk-variant rabies into southern California.     

Rabies and Canine Distemper Virus Epidemics in the Red Fox Population of Northern Italy (2006–2010)

Since 2006 the red fox (Vulpes vulpes) population in north-eastern Italy has experienced an epidemic of canine distemper virus (CDV). Additionally, in 2008, after a thirteen-year absence from Italy, fox rabies was re-introduced in the Udine province at the national border with Slovenia. Disease intervention strategies are being developed and implemented to control rabies in this area and minimise risk to human health. Here we present empirical data and the epidemiological picture relating to these epidemics in the period 2006–2010. Of important significance for epidemiological studies of wild animals, basic mathematical models are developed to exploit information collected from the surveillance program on dead and/or living animals in order to assess the incidence of infection. These models are also used to estimate the rate of transmission of both diseases and the rate of vaccination, while correcting for a bias in early collection of CDV samples. We found that the rate of rabies transmission was roughly twice that of CDV, with an estimated effective contact between infected and susceptible fox leading to a new infection occurring once every 3 days for rabies, and once a week for CDV. We also inferred that during the early stage of the CDV epidemic, a bias in the monitoring protocol resulted in a positive sample being almost 10 times more likely to be collected than a negative sample. We estimated the rate of intake of oral vaccine at 0.006 per day, allowing us to estimate that roughly 68% of the foxes would be immunised. This was confirmed by field observations. Finally we discuss the implications for the eco-epidemiological dynamics of both epidemics in relation to control measures.     

Origins of the rabies viruses associated with an outbreak in Newfoundland during 2002-2003

After being free of rabies of terrestrial mammals since 1988, an outbreak of rabies occurred on the Island of Newfoundland in December 2002 and continued into the middle of 2003. Twenty-one cases, all due to the arctic fox strain of rabies virus, were reported. To explore the immediate origins of this outbreak, viruses from the Newfoundland epizootic were genetically compared to two other rabies viruses recovered in mid-2002 from Cartwright, a mainland coastal community near the Island. While all Island isolates from the 2002-03 outbreak were genetically very similar, consistent with a single introduction from the mainland, they were phylogenetically quite distant from the two samples from Cartwright. A broader-based study examined the relationships between the Island viruses and arctic fox strain viruses originating from across Canada over a period of 14 yr. This analysis indicated that the Newfoundland outbreak viruses were most similar to a variant identified in Labrador in 2004 but also widely distributed in northern Quebec both before and after the Newfoundland incursion. The eastern coastline of mainland Labrador has harbored a particularly large number of variants during the study period, some of which have not been detected elsewhere. A small number of Greenland isolates included in this study were dispersed within the clades of the Canadian samples rather than forming a discrete cluster, an observation that may underline the relative ease of movement of the rabies arctic lineage between these two countries as a result of animal movements over pack ice.     

Modeling control of rabies outbreaks in red fox populations to evaluate culling,vaccination, and vaccination combined with fertility control

A predictive model of spread and control of rabies in red fox (Vulpes vulpes) populations was used to evaluate efficacy of culling, oral vaccination, and oral vaccination and fertility control (V + FC) as rabies control strategies. In addition, effects of season, fox population density, and a delay in starting control were modeled. At fox densities of 0.5 fox families/km2 or greater, a single oral vaccination campaign with bait uptake rates of less than 50% resulted in ineffective rabies control. An uptake rate of at least 80% was required to give a better than 80% chance of eliminating rabies. Vaccination was least effective at controlling rabies if applied 1 or 2 mo before the foxes gave birth. Seasonal timing of poison or V + FC had little effect on efficacy, which was always more successful than the oral vaccination alone. The longer the delay between the simulated start of the rabies infection and the application of a single vaccination campaign, the less successful was the control, particularly at the higher fox densities tested. At a fox density of 0.25 families/km2, all the strategies were equally successful at eliminating rabies. At higher fox densities V + FC was slightly less successful than culling, whereas vaccination-only was considerably less successful. The sole use of vaccination is not considered a viable control method for areas with high fox densities. The model suggests that an area of culling centered on the disease focus, plus an outer ring of vaccine or V + FC, could be the best strategy to control a point-source wildlife rabies outbreak.     

The Feasibility of Canine Rabies Elimination in Africa: Dispelling Doubts with Data

Background

Canine rabies causes many thousands of human deaths every year in Africa, and continues to increase throughout much of the continent.

Methodology/Principal Findings

This paper identifies four common reasons given for the lack of effective canine rabies control in Africa: (a) a low priority given for disease control as a result of lack of awareness of the rabies burden; (b) epidemiological constraints such as uncertainties about the required levels of vaccination coverage and the possibility of sustained cycles of infection in wildlife; (c) operational constraints including accessibility of dogs for vaccination and insufficient knowledge of dog population sizes for planning of vaccination campaigns; and (d) limited resources for implementation of rabies surveillance and control. We address each of these issues in turn, presenting data from field studies and modelling approaches used in Tanzania, including burden of disease evaluations, detailed epidemiological studies, operational data from vaccination campaigns in different demographic and ecological settings, and economic analyses of the cost-effectiveness of dog vaccination for human rabies prevention.

Conclusions/Significance

We conclude that there are no insurmountable problems to canine rabies control in most of Africa; that elimination of canine rabies is epidemiologically and practically feasible through mass vaccination of domestic dogs; and that domestic dog vaccination provides a cost-effective approach to the prevention and elimination of human rabies deaths.     

Predictive spatial dynamics and strategic planning for raccoon rabies emergence in Ohio

Rabies is an important public health concern in North America because of recent epidemics of a rabies virus variant associated with raccoons. The costs associated with surveillance, diagnostic testing, and post-exposure treatment of humans exposed to rabies have fostered coordinated efforts to control rabies spread by distributing an oral rabies vaccine to wild raccoons. Authorities have tried to contain westward expansion of the epidemic front of raccoon-associated rabies via a vaccine corridor established in counties of eastern Ohio, western Pennsylvania, and West Virginia. Although sporadic cases of rabies have been identified in Ohio since oral rabies vaccine distribution in 1998, the first evidence of a significant breach in this vaccine corridor was not detected until 2004 in Lake County, Ohio. Herein, we forecast the spatial spread of rabies in Ohio from this breach using a stochastic spatial model that was first developed for exploratory data analysis in Connecticut and next used to successfully hind-cast wave-front dynamics of rabies spread across New York. The projections, based on expansion from the Lake County breach, are strongly affected by the spread of rabies by rare, but unpredictable long-distance translocation of rabid raccoons; rabies may traverse central Ohio at a rate 2.5-fold greater than previously analyzed wildlife epidemics. Using prior estimates of the impact of local heterogeneities on wave-front propagation and of the time lag between surveillance-based detection of an initial rabies case to full-blown epidemic, specific regions within the state are identified for vaccine delivery and expanded surveillance effort.     

Concluding Remarks

Rabies seems to persist throughout most arctic regions, and the northern parts of Norway, Sweden and Finland, is the only part of the Arctic where rabies has not been diagnosed in recent time. The arctic fox is the main host, and the same arctic virus variant seems to infect the arctic fox throughout the range of this species. The epidemiology of rabies seems to have certain common characteristics in arctic regions, but main questions such as the maintenance and spread of the disease remains largely unknown. The virus has spread and initiated new epidemics also in other species such as the red fox and the racoon dog. Large land areas and cold climate complicate the control of the disease, but experimental oral vaccination of arctic foxes has been successful. This article summarises the current knowledge and the typical characteristics of arctic rabies including its distribution and epidemiology.