Raccoon rabies outbreak in Hamilton, Ontario: A progress report

Assessing the Efficiency of Local Rabies Vaccination Strategies for Raccoons (Procyon lotor) in an Urban Setting

Raccoon rabies virus (RRV) has been managed using multiple vaccination strategies, including oral rabies vaccination and trap-vaccinate-release (TVR). Identifying a rabies vaccination strategy for an area is a nontrivial task. Vaccination strategies differ in the amount of effort and monetary costs required to achieve a particular level of vaccine seroprevalence (efficiency). Simulating host movement relative to different vaccination strategies in silico can provide a useful tool for exploring the efficiency of different vaccination strategies. We refined a previously developed individual-based model of raccoon movement to evaluate vaccination strategies for urban Hamilton, Ontario, Canada. We combined different oral rabies vaccination baiting (hand baiting, helicopter, and bait stations) with TVR strategies and used GPS data to parameterize and simulate raccoon movement in Hamilton. We developed a total of 560 vaccination strategies, in consultation with the Ontario Ministry of Natural Resources and Forestry, for RRV control in Hamilton. We documented the monetary costs of each vaccination strategy and estimated the population seroprevalence. Intervention costs and seroprevalence estimates were used to calculate the efficiency of each strategy to meet targets set for the purpose of RRV control. Estimated seroprevalence across different strategies varied widely, ranging from less than 5% to more than 70%. Increasing bait densities (distributed using by hand or helicopter) led to negligible increase in seroprevalence. Helicopter baiting was the most efficient and TVR was the least efficient, but helicopter-based strategies led to lower levels of seroprevalence (6-12%) than did TVR-based strategies (17-70%). Our simulations indicated that a mixed strategy including at least some TVR may be the most efficient strategy for a local urban RRV control program when seroprevalence levels >30% may be required. Our simulations provide information regarding the efficiency of different vaccination strategies for raccoon populations, to guide local RRV control in urban settings.

Are rabid raccoons (Procyon lotor) ready for the rapture? Determining the geographic origin of rabies virus-infected raccoons using RADcapture and microhaplotypes

North America is recognized for the exceptional richness of rabies virus (RV) wildlife reservoir species. Management of RV is accomplished through vaccination targeting mesocarnivore reservoir populations, such as the raccoon (Procyon lotor) in Eastern North America. Raccoons are a common generalist species, and populations may reach high densities in developed areas, which can result in contact with humans and pets with potential exposures to the raccoon variant of RV throughout the eastern United States. Understanding the spatial movement of RV by raccoon populations is important for monitoring and refining strategies supporting the landscape-level control and local elimination of this lethal zoonosis. We developed a high-throughput genotyping panel for raccoons based on hundreds of microhaplotypes to identify population structure and genetic diversity relevant to rabies management programs. Throughout the eastern United States, we identified hierarchical population genetic structure with clusters that were connected through isolation-by-distance. We also illustrate that this genotyping approach can be used to support real-time management priorities by identifying the geographic origin of a rabid raccoon that was collected in an area of the United States that had been raccoon RV-free for 8 years. The results from this study and the utility of the microhaplotype panel and genotyping method will provide managers with information on raccoon ecology that can be incorporated into future management decisions.

Comparing Control Intervention Scenarios for Raccoon Rabies in Southern Ontario between 2015 and 2025

The largest outbreak of raccoon rabies in Canada was first reported in Hamilton, Ontario, in 2015 following a probable translocation event from the United States. We used a spatially-explicit agent-based model to evaluate the effectiveness of provincial control programs in an urban-centric outbreak if control interventions were used until 2025, 2020, or never used. Calibration tests suggested that a seroprevalence of protective rabies antibodies 2.1 times higher than that inferred from seroprevalence in program assessments was required in simulations to replicate observed raccoon rabies cases. Our simulation results showed that if control interventions with an adjusted seroprevalence were used until 2025 or 2020, the probability of rabies elimination due to control intervention use was 49.2% and 42.1%, respectively. However, if controls were never used, the probability that initial rabies cases failed to establish a sustained outbreak was only 18.2%. In simulations where rabies was not successfully eliminated, using control interventions until 2025 resulted in 67% fewer new infections compared to only applying controls until 2020 and in 90% fewer new infections compared to no control intervention use. However, the model likely underestimated rabies elimination rates since we did not adjust for adaptive control strategies in response to changes in rabies distributions and case numbers, as well as extending control interventions past 2025. Our agent-based model offers a cost-effective strategy to evaluate approaches to rabies control applications.

Assessment of One Health Knowledge, Animal Welfare Implications, and Emergency Preparedness Considerations for Effective Public Health Response

OBJECTIVES

Information on knowledge of public health professionals about health aspects of the human-animal interface, referred to as One Health, is limited. The objective of this study was to identify factors associated with animal welfare attitudes, practices, and One Health awareness among US Public Health Service (USPHS) officers to assess preparedness for public health response.

METHODS

USPHS officers participated in an online, self-administered survey from February 15 through March 2, 2018. A total of 1133 of 6474 (17.5%) USPHS officers responded. We collected information on officers' demographic characteristics, animal welfare attitudes and practices, volunteer and work exposure to animals, and One Health knowledge. We compared (1) One Health knowledge and animal work exposure (deployment, regular assignment, or none) and (2) animal welfare importance and animal work exposure. To adjust for demographic characteristics associated with One Health knowledge, we used multivariable logistic regression.

RESULTS

One-third of nonveterinary officers reported encountering animals during deployment, and 65% reported that animal welfare was very or extremely important. We found no difference in One Health knowledge between nonveterinary officers who participated in deployments involving animals and nonveterinary officers who had no work exposure to animals (adjusted odds ratio [aOR] = 1.11; 95% CI, 0.71-1.75). Nonveterinary officers who participated in animal-related public health activities during regular assignment were more likely to have One Health knowledge than nonveterinary officers who had no work exposure to animals (aOR = 7.88; 95% CI, 5.36-11.59).

CONCLUSIONS

One Health knowledge and awareness should be further explored in the current US public health workforce to identify training needs for emergency preparedness and other collaborative opportunities.

Local Surveillance and Control of Raccoon Rabies Virus in Striped Skunks (Mephitis mephitis) in Southwestern New Brunswick, Canada

Targeted surveillance for raccoon rabies virus was conducted between February and May 2017, near Waweig, New Brunswick, Canada, in response to detection of a rabid striped skunk (Mephitis mephitis) on 8 February 2017. A total of six skunks, 11 raccoons (Procyon lotor), and two porcupines (Erethizon dorsatum) were live-trapped, euthanized, and tested for rabies virus antigens using the direct rapid immunohistochemical test. Of these, only two skunks tested positive for rabies. All three rabid skunks came from the same location, an abandoned barn used as a denning site. Four of five skunks removed from this barn were males. Feeding, aggression, extreme response to noise and light stimuli, and exposure to porcupine quills were observed in two rabid skunks. No additional cases of rabies in wildlife were detected in the area since 8 March 2017. A targeted surveillance approach that removed potentially infected wildlife followed by localized oral rabies vaccine distribution was implemented in this locality.

Update on lyssaviruses and rabies: will past progress play as prologue in the near term towards future elimination?

Rabies is an ancient, much-feared, and neglected infectious disease. Caused by pathogens in the family Rhabdoviridae, genus Lyssavirus, and distributed globally, this viral zoonosis results in tens of thousands of human fatalities and millions of exposures annually. All mammals are believed susceptible, but only certain taxa act as reservoirs. Dependence upon direct routing to, replication within, and passage from the central nervous system serves as a basic viral strategy for perpetuation. By a combination of stealth and subversion, lyssaviruses are quintessential neurotropic agents and cause an acute, progressive encephalitis. No treatment exists, so prevention is the key. Although not a disease considered for eradication, something of a modern rebirth has been occurring within the field as of late with regard to detection, prevention, and management as well as applied research. For example, within the past decade, new lyssaviruses have been characterized; sensitive and specific diagnostics have been optimized; pure, potent, safe, and efficacious human biologics have improved human prophylaxis; regional efforts have controlled canine rabies by mass immunization; wildlife rabies has been controlled by oral rabies vaccination over large geographic areas in Europe and North America; and debate has resumed over the controversial topic of therapy. Based upon such progress to date, there are certain expectations for the next 10 years. These include pathogen discovery, to uncover additional lyssaviruses in the Old World; laboratory-based surveillance enhancement by simplified, rapid testing; anti-viral drug appearance, based upon an improved appreciation of viral pathobiology and host response; and improvements to canine rabies elimination regionally throughout Africa, Asia, and the Americas by application of the best technical, organizational, economic, and socio-political practices. Significantly, anticipated Gavi support will enable improved access of human rabies vaccines in lesser developed countries at a national level, with integrated bite management, dose-sparing regimens, and a 1 week vaccination schedule.

Public Veterinary Medicine: Public Health: Rabies surveillance in the United States during 2018

OBJECTIVE

To describe rabies and rabies-related events occurring during 2018 in the United States.

ANIMALS

All animals submitted for laboratory diagnosis of rabies in the United States during 2018.

PROCEDURES

State and territorial public health departments provided data on animals submitted for rabies testing in 2018. Data were analyzed temporally and geographically to assess trends in domestic animal and wildlife rabies cases.

RESULTS

During 2018, 54 jurisdictions reported 4,951 rabid animals to the CDC, representing an 11.2% increase from the 4,454 rabid animals reported in 2017. Texas (n = 695 [14.0%]), Virginia (382 [7.7%]), Pennsylvania (356 [7.2%]), North Carolina (332 [6.7%]), Colorado (328 [6.6%]), and New York (320 [6.5%]) together accounted for almost half of all rabid animals reported in 2018. Of the total reported rabies cases, 4,589 (92.7%) involved wildlife, with bats (n = 1,635 [33.0%]), raccoons (1,499 [30.3%]), skunks (1,004 [20.3%]), and foxes (357 [7.2%]) being the major species. Rabid cats (n = 241 [4.9%]) and dogs (63 [1.3%]) accounted for > 80% of rabid domestic animals reported in 2018. There was a 4.6% increase in the number of samples submitted for testing in 2018, compared with the number submitted in 2017. Three human rabies deaths were reported in 2018, compared with 2 in 2017.

CONCLUSIONS AND CLINICAL RELEVANCE

The overall number of animal rabies cases increased from 2017 to 2018. Laboratory diagnosis of rabies in animals is critical to ensure that human rabies postexposure prophylaxis is administered judiciously.

Ouch! A cross-sectional study investigating self-reported human exposure to dog bites in rural and urban households in southern Ontario, Canada

This study investigated self-reported dog bites in humans in rural and urban households in southern Ontario, Canada. Our objectives were to determine, and compare, the incidence of dog bites in rural and urban households, and to describe the profile of bite victims, biting dogs, and the proportion of biting dogs that respondents self-reported as being not up to date on rabies vaccination. We conducted a cross-sectional observational study using an online questionnaire. The 2,006 respondents, each representing one household, included 1,002 rural and 1,004 urban residences. The incidence risk of at least one person in the household being bitten over the previous year in rural households (6.09% per year) was less than in urban households (10.76% per year). In 53.20% of households from which at least one person had been bitten within the past year, only a single person had been bitten. Mostly, victims were 25 to 34 years old (21.67%), male (54.19%), and playing with or interacting with the biting dog at the time of the incident (59.11%). Most biting dogs were 3 to 5 years old (32.02%), males (53.69%), and unleashed (76.85%). Based on self-reporting by respondents, 83.33% of respondent-owned biting dogs were vaccinated against rabies at the time of the biting incident. Irrespective of dog ownership, the odds of an individual in a rural household being bitten by a dog were 0.53 (95% CI: 0.38-0.73) the odds for an individual in an urban household. Dog bites constitute a serious, yet preventable, public health concern that requires targeted, community-specific efforts. Public health organizations could consider findings in developing messaging, particularly as we highlight biting dogs reported by their owners as not up to date on rabies vaccination.

A long-distance translocation initiated an outbreak of raccoon rabies in Hamilton, Ontario, Canada

Despite proactive measures to prevent raccoon rabies entering Canada from the United States, several incursions of this disease have occurred. The largest outbreak, first reported in December 2015 in the city of Hamilton, Ontario, has resulted in the reporting of 449 animal cases as of December 31, 2018. Initial phylogenetic studies on the index case suggested that this outbreak was not due to local cross-border spread from the Niagara region of the United States where raccoon rabies has persisted for several years. Phylogenetic analysis of whole genome sequences of a viral collection from the Hamilton area and several US states indicates that a long-distance translocation of a diseased animal from southeastern New York State was responsible for this incursion. The role of the skunk as a potential secondary host supporting persistence and / or spread of the virus is also examined.

Distinct variants of rabies virus are harbored by several wildlife species across North America. The variant associated with the raccoon host is especially problematic given its rapid spread throughout the eastern seaboard of the United States over the second half of the 20^th century and the high population density of this species in urban habitats that raises the potential for disease spread to both companion animals and their owners. Accordingly, extensive efforts to control raccoon rabies have been undertaken at many jurisdictional levels. This study uses current methods of genome analysis to explore the origins of a raccoon rabies outbreak in and around the city of Hamilton, Ontario, Canada, located close to the border with western New York state. In contrast to previous Canadian outbreaks of raccoon rabies, which were due to cross-border spread of the virus, this study demonstrates that the incursion into the Hamilton area was the result of a long-distance animal translocation from south-eastern New York. The implications of this event for strategies to control raccoon rabies are discussed.

Rapid identification of the raccoon rabies virus variant using a real-time reverse-transcriptase polymerase chain reaction

The raccoon-associated variant of rabies virus (RRV) is enzootic throughout the eastern seaboard of the United States with frequent incursions into Canada. Many wildlife management agencies are actively engaged in control programmes targeting elimination of this disease and rapid identification of raccoon rabies cases is crucial to the success of these operations. This report documents the development of a reverse transcriptase real-time PCR (RT-qPCR) that specifically identifies this rabies virus variant (RRV RT-qPCR) and which can be readily multiplexed with a generic rabies virus RT-qPCR for use as a typing tool. Using a large collection of rabies virus samples representative of the variants circulating around the world, but with a focus on those occurring in the Americas, the RRV RT-qPCR was 100% sensitive and 99.31% specific. To further apply these assays for diagnostic purposes, addition of an RT-qPCR targeting the host β-actin mRNA, which serves as an internal amplification control, in a triplex format was shown to yield highly comparable results using a subset of our viral collection. Use of these assays for early and accurate identification of this viral variant will help to optimize the utilization of resources required for control of this disease.