Modeling raccoon (Procyon lotor) habitat connectivity to identify potential corridors for rabies spread

The United States Department of Agriculture (USDA), Animal and Plant Health Inspection Service (APHIS), Wildlife Services National Rabies Management Program has conducted cooperative oral rabies vaccination (ORV) programs since 1997. Understanding the eco-epidemiology of raccoon (Procyon lotor) variant rabies (raccoon rabies) is critical to successful management. Pine (Pinus spp.)-dominated landscapes generally support low relative raccoon densities that may inhibit rabies spread. However, confounding landscape features, such as wetlands and human development, represent potentially elevated risk corridors for rabies spread, possibly imperiling enhanced rabies surveillance and ORV planning. Raccoon habitat suitability in pine-dominated landscapes in Massachusetts, Florida, and Alabama was modeled by the maximum entropy (Maxent) procedure using raccoon presence, and landscape and environmental data. Replicated (n = 100/state) bootstrapped Maxent models based on raccoon sampling locations from 2012–2014 indicated that soil type was the most influential variable in Alabama (permutation importance PI = 38.3), which, based on its relation to landcover type and resource distribution and abundance, was unsurprising. Precipitation (PI = 46.9) and temperature (PI = 52.1) were the most important variables in Massachusetts and Florida, but these possibly spurious results require further investigation. The Alabama Maxent probability surface map was ingested into Circuitscape for conductance visualizations of potential areas of habitat connectivity. Incorporating these and future results into raccoon rabies containment and elimination strategies could result in significant cost-savings for rabies management here and elsewhere

Non-Lethal Management to Reduce Conflicts with Winter Urban Crow Roosts in New York: 2002 - 2007

American crow populations have increased steadily since 1966 in many parts of the U.S. Large winter congregations of crows in urban environments have resulted in an increased number of requests for assistance in managing nocturnal roosts in New York. In 2002, the USDA APHIS Wildlife Services program initiated a large-scale non-lethal winter roost dispersal program in Troy, New York. Since that time, similar programs have been implemented in 4 other cities in New York to manage crow roosts ranging in size from 8,000 - 63,000 individuals. The goals of the programs were to minimize noise, accumulations of crow feces around residences, strong odors associated with droppings, property damage, clean-up costs, and potential threats to human health and safety. The primary management strategy relied on dispersing concentrated crow populations from high-impact high-conflict areas, to low-impact low-conflict areas. An integrated management program using pyrotechnics, amplified recorded crow distress calls, and hand-held lasers was implemented to successfully disperse local crow roosts, reducing populations at the majority of core roost sites each year by more than 98%. In some instances, significant reductions in crow numbers and associated damage persisted \u3e8 weeks after management without additional interventions, although most sites required multiple additional “spot treatments.” High-profile urban wildlife management projects of this type require multiple meetings with key stakeholders and the public and often attract intense media interest, adding complexity to these programs. We provide summary information from 5 cities in New York documenting crow management techniques, intensity of effort, number of interventions required to relocate crow populations, and key lessons learned regarding science-based project documentation, project transparency, communication, and the need for long-term adaptive management strategies to meet project goals

Rabies Management Implications Based on Raccoon Population Density Indexes

An estimate or index of target species density is important in determining oral rabies vaccination (ORV) bait densities to control and eliminate specific rabies variants. From 1997–2011, we indexed raccoon (Procyon lotor) densities 253 times based on cumulative captures on 163 sites from Maine to Alabama, USA, near ORV zones created to prevent raccoon rabies from spreading to new areas. We conducted indexing under a common cage trapping protocol near the time of annual ORV to aid in bait density decisions. Unique raccoons (n = 8,415) accounted for 68.0% of captures (n = 12,367). We recaptured raccoons 2,669 times. We applied Schnabel and Huggins mark‐recapture models on sites with ≥3 years of capture data and ≥25% recaptures as context for raccoon density indexes (RDIs). Simple linear relationships between RDIs and mark‐recapture estimates supported application of our 2 index. Raccoon density indexes ranged from 0.0–56.9 raccoons/km . For bait density decisions, we evaluated RDIs in the following 4 raccoon density groups, which were statistically different: (0.0–5.0 [n = 70], 5.1–15.0 [n = 129], 15.1–25.0 [n = 31], and \u3e25.0 raccoons/km2 [n = 23]). Mean RDI was positively associated with a higher percentage of developed land cover and a lower percentage of evergreen forest. Non‐target species composition (excluding recaptured raccoons) accounted for 32.0% of captures. Potential bait competitors accounted for 76.5% of non‐targets. The opossum (Didelphis virginiana) was the primary potential bait competitor from 27°N to 44°N latitude, north of which it was numerically replaced by the striped skunk (Mephitis mephitis). We selected the RDI approach over mark-recapture methods because of costs, geographic scope, staff availability, and the need for supplemental serologic samples. The 4 density groups provided adequate sensitivity to support bait density decisions for the current 2 bait density options. Future improvements to the method include providing random trapping locations to field personnel to prevent trap clustering and marking non‐targets to better characterize bait competitors

FIELD TRIALS OF ONTARIO RABIES VACCINE BAIT IN THE NORTHEASTERN USA, 2012–14

In the US, rabies virus (RV) has been enzootic in raccoons (Procyon lotor) since the late 1940s. Oral rabies vaccination (ORV) was implemented in the 1990s to halt the spread of raccoon RV and continues to be used as a wildlife management tool. Our objective was to evaluate a recombinant human adenovirus–rabies virus glycoprotein vaccine in northern New York, Vermont, and New Hampshire over a 3-yr period, using changes in RV neutralizing antibody (RVNA) seroprevalence in raccoon populations as an immunologic index of ORV impact. Vaccine baits were distributed at 75 baits/km2 and 750-m flight-line spacing in the study area. Animal sampling occurred during 10-d intervals pre- and post-ORV during 2012–14 within eight study cells: four northern cells had a history of ORV with a different vaccine for 3 or more years prior and four southern cells were ORV naive. Baseline raccoon RVNA seroprevalence was 27.3% (n=1,079, 95% confidence interval [CI]: 24.8–30.1) before ORV in 2012. Raccoon RVNA seroprevalence averaged 68.5% (n=1,551, 95% CI: 66.2–70.8) post-ORV during the 3-yr study. The RVNA seroprevalence levels in this study were considered to be adequate for stopping raccoon RV transmission and supported and expanded the results from a West Virginia field trial, as well as earlier evaluations along the Canada–US border

Oral Rabies Vaccination in North America: Opportunities, Complexities, and Challenges

Steps to facilitate inter-jurisdictional collaboration nationally and continentally have been critical for implementing and conducting coordinated wildlife rabies management programs that rely heavily on oral rabies vaccination (ORV). Formation of a national rabies management team has been pivotal for coordinated ORV programs in the United States of America. The signing of the North American Rabies Management Plan extended a collaborative framework for coordination of surveillance, control, and research in border areas among Canada, Mexico, and the US. Advances in enhanced surveillance have facilitated sampling of greater scope and intensity near ORV zones for improved rabies management decision-making in real time. The value of enhanced surveillance as a complement to public health surveillance was best illustrated in Ohio during 2007, where 19 rabies cases were detected that were critical for the formulation of focused contingency actions for controlling rabies in this strategically key area. Diverse complexities and challenges are commonplace when applying ORV to control rabies in wild meso-carnivores. Nevertheless, intervention has resulted in notable successes, including the elimination of an arctic fox (Vulpes lagopus) rabies virus variant in most of southern Ontario, Canada, with ancillary benefits of elimination extending into Quebec and the northeastern US. Progress continues with ORV toward preventing the spread and working toward elimination of a unique variant of gray fox (Urocyon cinereoargenteus) rabies in west central Texas. Elimination of rabies in coyotes (Canis latrans) through ORV contributed to the US being declared free of canine rabies in 2007. Raccoon (Procyon lotor) rabies control continues to present the greatest challenges among meso-carnivore rabies reservoirs, yet to date intervention has prevented this variant from gaining a broad geographic foothold beyond ORV zones designed to prevent its spread from the eastern US. Progress continues toward the development and testing of new bait-vaccine combinations that increase the chance for improved delivery and performance in the diverse meso-carnivore rabies reservoir complex in the US

Predicted Wildlife Disease-Related Climate Change Impacts of Specific Concern to USDA APHIS Wildlife Services

USDA APHISWildlife Services plans for and responds to a variety of exigencies such as wildlife hazards to aircraft, disease emergence from wildlife translocations, oral rabies vaccine barrier compromises, and extreme weather events. These are often collaborative efforts with state and federal agencies and others. Climate change based in part on fossil fuel use and methane gas emissions has predictable as well as unknown consequences. As a federal leader in wildlife disease research and management, it is incumbent upon Wildlife Services to be current with the scientific literature; assess potential impacts and wildlife disease management intervention needs from predicted climate change scenarios; and outline a plan of preparedness to meet a variety of potential exigencies

ORAL RABIES VACCINATION VARIATION IN TETRACYCLINE BIOMARKING AMONG OHIO RACCOONS

Oral rabies vaccination (ORV) programs have traditionally relied on tetracycline marking as an index to bait uptake. Whether tetracycline serves well in this capacity depends on its deposition affinity and ability to be detected consistently among tissues selected for analysis from target species. We evaluated samples from 760 hunter-harvested raccoons (Procyon lotor) from areas in Ohio where ORV had been conducted during 1998, 1999, and 2001. Tetracycline marking was evaluated within and among first premolar (PM1), second premolar (PM2), and canine (CN) teeth, and mandibular bone (MB) by side (left versus right); and by tissue type. Tetracycline detection ranged from 6.5% in PM1 in 1998 to 56.3% in right-side MB in 2001. PM1 teeth were less frequently marked (21.7%) than PM2 (27.7%), CN (33.0%), or MB (42.0%). Tetracycline detection was similar in left and right PM1, PM2, and CN teeth, but differed in MB. Tetracycline marking was significantly different among all tissue types

Passive tracking stations as a method for providing rabies reservoir population information for oral rabies vaccination

Knowledge of wildlife population abundance and activity patterns is integral to sound management decisions. Traditional methods of determining population abundance include mark-recapture, catch/unit effort, aerial and ground counts, and harvest-based or removal efforts. Capture methods are labor intensive and expensive. Census methods are potentially expensive and are often impractical for many wildlife species. Harvest-derived population estimates are not useful where harvest is limited. Tracking or scent stations have been used to index wildlife activity and abundance, but the use of traditional scented-tracking stations may lead to biased population activity or abundance estimates. We built on previous evaluations of passive and scented tracking stations to determine their potential utility for providing raccoon and other carnivore population information to support decisions for wildlife rabies control in coastal pine-oak communities. Methods were evaluated through several small-scale studies conducted in southeastern Massachusetts. Passive tracking stations appear more sensitive to raccoon activity than scented tracking stations (1.38% of scented stations visited vs. 3.38% of passive stations) under apparently low raccoon population densities. Despite concerns over the utility of track-based indices, we recommend the use of passive tracking stations to index raccoon activity over scented tracking stations

Anatomy of the Cape Cod Oral Rabies Vaccination Program

Rabies remains a globally significant zoonotic disease, but rabies control is achievable under certain circumstances. Canine rabies has been eliminated from the U.S.; however, approximately 55,000 humans die annually worldwide from the disease. In the U.S., economic losses continue to be substantial and the risk to humans and domestic animals has not been eliminated. As an example of the complexity of rabies management, we describe a local rabies control program and efforts to restore Cape Cod, MA to terrestrial rabies-free status, after a 2004 oral rabies vaccination (ORV) barrier breach following 10 years of rabies-free status. The emergence of raccoon rabies in southeastern New England in 1992 prompted the U.S. Centers for Disease Control and Prevention, the Tufts Cummings School of Veterinary Medicine, and the Massachusetts Department of Public Health to begin an ORV program to reduce the occurrence of carnivore rabies in an area directly adjacent to the Cape Cod Canal. In 200 J, USDA APHIS Wildlife Services began full-time collaboration on the Cape Cod Oral Rabies Vaccination Program (CCORVP) as part of national wildlife rabies control efforts. The primary objective of the CCORVP was to use ORV in tandem with the physical barrier created by the Canal to prevent the spread of rabies to peninsular Cape Cod, a heavily-populated tourist destination southeast of Boston. After an increase in rabies cases within the traditional Cape Cod ORV zone, ORV bait distribution efforts were modified to reduce the risk of rabies spread onto the Cape. In spite of these modifications, raccoon rabies was detected for the first time on peninsular Cape Cod in March 2004. A trap-vaccinate-release campaign, removal of suspect raccoons and skunks, and expanded ORV efforts were unsuccessful in preventing the spread of the virus. Rabies surveillance became the priority of the Cape Cod Rabies Task Force. In 2006, rabies was finally detected at the eastern extremity of the peninsula In this paper, we summarize ORV efforts, explore possible causes tor the spread of raccoon rabies onto the Cape, summarize several small-scale Cape Cod rabies research projects, and suggest a 5-year plan for future Cape Cod rabies controls efforts

FIELD TRIALS OF ONTARIO RABIES VACCINE BAIT IN THE NORTHEASTERN USA, 2012–14

In the US, rabies virus (RV) has been enzootic in raccoons (Procyon lotor) since the late 1940s. Oral rabies vaccination (ORV) was implemented in the 1990s to halt the spread of raccoon RV and continues to be used as a wildlife management tool. Our objective was to evaluate a recombinant human adenovirus–rabies virus glycoprotein vaccine in northern New York, Vermont, and New Hampshire over a 3-yr period, using changes in RV neutralizing antibody (RVNA) seroprevalence in raccoon populations as an immunologic index of ORV impact. Vaccine baits were distributed at 75 baits/km2 and 750-m flight-line spacing in the study area. Animal sampling occurred during 10-d intervals pre- and post-ORV during 2012–14 within eight study cells: four northern cells had a history of ORV with a different vaccine for 3 or more years prior and four southern cells were ORV naive. Baseline raccoon RVNA seroprevalence was 27.3% (n=1,079, 95% confidence interval [CI]: 24.8–30.1) before ORV in 2012. Raccoon RVNA seroprevalence averaged 68.5% (n=1,551, 95% CI: 66.2–70.8) post-ORV during the 3-yr study. The RVNA seroprevalence levels in this study were considered to be adequate for stopping raccoon RV transmission and supported and expanded the results from a West Virginia field trial, as well as earlier evaluations along the Canada–US border