Evaluation of rabies virus characterization to enhance early detection of important rabies epizootic events in the United States

Dogs on the move: Estimating the risk of rabies in imported dogs in the United States, 2015-2022

BACKGROUND

Dog-mediated rabies virus variant (DMRVV), a zoonotic pathogen that causes a deadly disease in animals and humans, is present in more than 100 countries worldwide but has been eliminated from the United States since 2007. In the United States, the U.S. Centers for Disease Control and Prevention has recorded four instances of rabies in dogs imported from DMRVV-enzootic countries since 2015. However, it remains uncertain whether the incidence of DMRVV among imported dogs from these countries significantly surpasses that of domestically acquired variants among domestic U.S. dogs.

AIM

This evaluation aimed to estimate the number of dogs imported from DMRVV-enzootic countries and compare the risk of rabies between imported dogs and the U.S. domestic dog population.

MATERIALS AND METHODS

Data from the CDC's dog import permit system (implemented during 2021 under a temporary suspension of dog importation from DMRVV-enzootic countries) and U.S. Customs and Border Protection's Automated Commercial Environment system, each of which records a segment of dogs entering the U.S. from DMRVV-enzootic countries, was analysed. Additionally, we estimated the incidence rate of rabies in dogs imported from DMRVV-enzootic countries and compared it to the incidence rate within the general U.S. dog population, due to domestically acquired rabies variants, over the eight-year period (2015-2022).

RESULTS

An estimated 72,589 (range, 62,660-86,258) dogs were imported into the United States annually between 2015 and 2022 from DMRVV-enzootic countries. The estimated incidence rate of rabies was 16 times higher (range, 13.2-19.4) in dogs imported from DMRVV-enzootic countries than that estimated for domestically acquired rabies in the general U.S. dog population.

CONCLUSIONS

Preventing human exposure to dogs with DMRVV is a public health priority. The higher risk of rabies in dogs imported from DMRVV-enzootic countries supports the need for importation requirements aimed at preventing the reintroduction of DMRVV into the United States.

Evaluation of contingency actions to control the spread of raccoon rabies in Ohio and Virginia

The raccoon (Procyon lotor) variant of the rabies virus (RRV) is enzootic in the eastern United States and oral rabies vaccination (ORV) is the primary strategy to prevent and control landscape spread. Breaches of ORV management zones occasionally occur, and emergency "contingency" actions may be implemented to enhance local control. Contingency actions are an integral part of landscape-scale wildlife rabies management but can be very costly and routinely involve enhanced rabies surveillance (ERS) around the index case. We investigated two contingency actions in Ohio (2017-2019 and 2018-2021) and one in Virginia (2017-2019) using a dynamic, multi-method occupancy approach to examine relationships between specific management actions and RRV occurrence, including whether ERS was sufficient around the index case. The RRV occupancy was assessed seasonally at 100-km2 grids and we examined relationships across three spatial scales (regional management zone, RRV free regions, and local contingency areas). The location of a grid relative to the ORV management zone was the strongest predictor of RRV occupancy at the regional scale. In RRV free regions, the neighbor effect and temporal variability were most important in influencing RRV occupancy. Parenteral (hand) vaccination of raccoons was important across all three contingency action areas, but more influential in the Ohio contingency action areas where more raccoons were hand vaccinated. In the Virginia contingency action area, ORV strategies were as important in reducing RRV occupancy as a hand vaccination strategy. The management action to trap, euthanize, and test (TET) raccoons was an important method to increase ERS, yet the impacts of TET on RRV occupancy are not clear. The probability of detecting additional cases of RRV was exceptionally high (>0.95) during the season the index case occurred. The probability of detecting RRV through ERS declined in the seasons following initial TET efforts but remained higher after the contingency action compared to the ERS detection probabilities prior to index case incidence. Local RRV cases were contained within one year and eliminated within 2-3 years of each contingency action.

Rabies experts on demand: A cross-sectional study describing the use of a rabies telehealth service

Background

Rabies expert on demand (REOD) telehealth service is provided by the U.S. Centers for Disease Control and Prevention (CDC) to assist public health practitioners, health providers, and the public to interpret national and international rabies prevention guidelines. REOD is staffed by subject matter experts of the CDC Poxvirus and Rabies Branch to assess each unique situation and provide evidence-based guidance to stakeholders. This study aims to describe the utilization of a rabies telehealth system and provide insight into common consultations.

Methods

A cross-sectional study of the nature of inquiries to REOD was done using the data collected from September 1, 2017 to September 30, 2021. An inquiry tracking form and Microsoft Access database were developed to document all inquiries received. Inquired ones were summarized to determine the frequency of inquiries by month, category, and location.

Results

Over a 49-month period, REOD received 5228 inquiries. Peak inquiries (n = 108) occurred during August 2019. The most frequent inquiries received pertained to risk assessment and management of rabies exposures (n = 1109), requests for testing assistance (n = 912), consultation for suspected human rabies (n = 746), rabies exposures and post-bite treatment occurring internationally (n = 310), and consultation for deviations in the recommended pre- and postexposure prophylaxis regimen (n = 300).

Conclusion

REOD is a global resource for consultation related to managing rabies exposures, diagnostic issues, and rabies control strategies. REOD is a regularly utilized CDC service, as the demand for up-to-date rabies guidance remains high. REOD fulfills a critical role for the interpretation and consultation on rabies prevention guidelines to stakeholder.

Detection of rabies virus via exciton energy transfer between CdTe quantum dots and Au nanoparticles

Rabies is a fatal encephalitis caused by the rabies virus. The diagnosis of the disease depends in large part on the exposure history of the victim and clinical manifestations of the disease. Rapid rabies diagnosis is an important step in its prevention and control. Therefore, for accurate and timely diagnosis and prevention of rabies, we developed nanomaterials for a novel photoelectrochemical biosensing approach (PBA) for the rapid and reliable diagnosis of rabies virus. This approach uses high-efficiency exciton energy transfer between cadmium telluride quantum dots and Au nanoparticles and is low cost, and easy to miniaturize. By constructing PBA, rabies virus can be detected quickly and with a high degree of sensitivity and specificity; the minimum detection concentration limit for rabies virus is approximately 2.16 ffu/mL of rabies virus particles, or 2.53 × 10¹ fg/mL of rabies virus RNA. PBA could also detect rabies virus in the brain and lung tissue from rabid dogs and mice with better sensitivity than RT-PCR.

Rabies surveillance in the United States during 2019

OBJECTIVE

To provide epidemiological information on animal and human cases of rabies occurring in the United States during 2019 and summaries of 2019 rabies surveillance for Canada and Mexico.

ANIMALS

All animals submitted for laboratory diagnosis of rabies in the United States during 2019.

PROCEDURES

State and territorial public health departments and USDA Wildlife Services provided data on animals submitted for rabies testing in the United States during 2019. Data were analyzed temporally and geographically to assess trends in domestic and wildlife rabies cases.

RESULTS

During 2019, 53 jurisdictions submitted 97,523 animal samples for rabies testing, of which 94,770 (97.2%) had a conclusive (positive or negative) test result. Of these, 4,690 tested positive for rabies, representing a 5.3% decrease from the 4,951 cases reported in 2018. Texas (n = 565 [12.0%]), New York (391 [8.3%]), Virginia (385 [8.2%]), North Carolina (315 [6.7%]), California (276 [5.9%]), and Maryland (269 [5.7%]) together accounted for almost half of all animal rabies cases reported in 2019. Of the total reported rabid animals, 4,305 (91.8%) were wildlife, with raccoons (n = 1,545 [32.9%]), bats (1,387 [29.6%]), skunks (915 [19.5%]), and foxes (361 [7.7%]) as the primary species confirmed with rabies. Rabid cats (n = 245 [5.2%]) and dogs (66 [1.4%]) accounted for > 80% of rabies cases involving domestic animals in 2019. No human rabies cases were reported in 2019.

CONCLUSIONS AND CLINICAL RELEVANCE

The overall number of animal rabies cases decreased from 2018 to 2019. Laboratory diagnosis of rabies in animals is critical to ensure that human rabies postexposure prophylaxis is administered judiciously.

Prioritisation of areas for early detection of southward movement of arctic fox rabies based on historical surveillance data in Quebec, Canada

Arctic rabies virus variant (ARVV) is enzootic in Quebec (Canada) north of the 55th parallel. With climate change, increased risk of re-incursion of ARVV in more densely populated southern regions raises public and animal health concerns. The objective of this study was to prioritise geographical areas to target for an early detection of ARVV incursion south of the 55th parallel based on the historical spatio-temporal trends of reported rabies in foxes in Quebec. Descriptive analyses of fox rabies cases from 1953 to 2017 were conducted. Three periods show increases in the number of fox rabies cases in southern regions and indicate incursion from northern areas or neighbouring provinces. The available data, particularly in central and northern regions of the province, were scarce and of low spatial resolution, making it impossible to identify the path of spread with precision. Hence, we investigated the use of multiple criteria, such as historical rabies cases, human population density and red fox (Vulpes vulpes) relative abundance, to prioritise areas for enhanced surveillance. This study underscores the need to define and maintain new criteria for selecting samples to be analysed in order to detect rapidly ARVV cases outside the current enzootic area and any potential re-incursion of the virus into central and southern regions of the province.

Portable Rabies Virus Sequencing in Canine Rabies Endemic Countries Using the Oxford Nanopore MinION

As countries with endemic canine rabies progress towards elimination by 2030, it will become necessary to employ techniques to help plan, monitor, and confirm canine rabies elimination. Sequencing can provide critical information to inform control and vaccination strategies by identifying genetically distinct virus variants that may have different host reservoir species or geographic distributions. However, many rabies testing laboratories lack the resources or expertise for sequencing, especially in remote or rural areas where human rabies deaths are highest. We developed a low-cost, high throughput rabies virus sequencing method using the Oxford Nanopore MinION portable sequencer. A total of 259 sequences were generated from diverse rabies virus isolates in public health laboratories lacking rabies virus sequencing capacity in Guatemala, India, Kenya, and Vietnam. Phylogenetic analysis provided valuable insight into rabies virus diversity and distribution in these countries and identified a new rabies virus lineage in Kenya, the first published canine rabies virus sequence from Guatemala, evidence of rabies spread across an international border in Vietnam, and importation of a rabid dog into a state working to become rabies-free in India. Taken together, our evaluation highlights the MinION's potential for low-cost, high volume sequencing of pathogens in locations with limited resources.

Evaluation of rabies virus characterization to enhance early detection of important rabies epizootic events in the United States

OBJECTIVE

To evaluate rabies virus (RABV) characterization data obtained from animal specimens submitted to the US public health rabies surveillance system and propose a standardized approach to sample selection for RABV characterization that could enhance early detection of important rabies epizootic events in the United States.

SAMPLE

United States public health rabies surveillance system data collected from January 1, 2010, through December 31, 2015.

PROCEDURES

Data were reviewed to identify RABV-positive specimens for which virus characterization would likely provide information regarding any of 4 overarching events (discovery of novel variants, translocation of RABV variants, host-shift events, and any unusual rabies-related event) that could substantially alter animal rabies epizootiology in the United States. These specimens were designated as specimens of epizootiological importance (SEIs). Estimates of the additional number of specimens that public health laboratories could expect to process each year if all SEIs underwent RABV characterization were calculated.

RESULTS

During the 6-year period, the mean annual number of SEIs was 855 (95% CI, 739 to 971); the mean number of SEIs that underwent virus characterization was 270 (95% CI, 187 to 353). Virus characterization of all SEIs would be expected to increase the public health laboratories' test load by approximately 585 (95% CI, 543 to 625) specimens/y.

CONCLUSIONS AND CLINICAL RELEVANCE

Prioritization of RABV characterization of SEIs may improve early detection of rabies events associated with RABV host shifts, variant translocations, and importation. Characterization of SEIs may help refine wildlife rabies management practices. Each public health laboratory should evaluate testing of SEIs to ensure diagnostic laboratory capacity is not overstretched.

Evaluation of species identification and rabies virus characterization among bat rabies cases in the United States

OBJECTIVE

To evaluate species identification and rabies virus (RABV) characterization among samples from bats submitted for rabies testing in the United States and assess whether a standardized approach to specimen selection for RABV characterization could enhance detection of a sentinel event in virus dissemination among bats.

SAMPLE

United States public health rabies surveillance system data collected in January 2010 through December 2015.

PROCEDURES

The number of rabies-tested bats for which species was reported and the number of RABV-positive samples for which virus characterization would likely provide information regarding introduction of novel RABV variants and translocation and host-shift events were calculated. These specimens were designated as specimens of epizootiological importance (SEIs). Additionally, the estimated test load that public health laboratories could expect if all SEIs underwent RABV characterization was determined.

RESULTS

Species was reported for 74,928 of 160,017 (47%) bats submitted for rabies testing. Identified SEIs were grouped in 3 subcategories, namely nonindigenous bats; bats in southern border states, Florida, Puerto Rico, and the US Virgin Islands; and bats of species that are not commonly found to be inflected with RABV. Annually, 692 (95% CI, 600 to 784) SEIs were identified, of which only 295 (95% CI, 148 to 442) underwent virus characterization. Virus characterization of all SEIs would be expected to increase public health laboratories' overall test load by 397 (95% CI, 287 to 506) samples each year.

CONCLUSIONS AND CLINICAL RELEVANCE

Species identification and RABV characterization may aid detection of a sentinel event in bat RABV dissemination. With additional resources, RABV characterization of all SEIs as a standardized approach to testing could contribute to knowledge of circulating bat RABV variants.