Wildlife Disease and Toxicology III

Contributed Paper
ROOM: Rooms 18 – Cochiti and 30 – Taos Combined

1:10PM More Offal Than We Thought: Extended Availability of Lead to Wildlife from Hunter-Discarded Gut Piles.
Margaret G. Rheude
Lead ammunition from hunting is a known environmental contaminant, and wildlife poisoning from lead consumption is well-documented. While exposure and impacts to carnivores and raptors is readily observed, the degree of exposure and ingestion of lead by songbirds and other small wildlife is uncertain. We posed two questions: Do winter resident songbirds and small wildlife feed on discarded deer gut piles, and do gut piles persist long enough on the landscape to become available for consumption. In the Minnesota Valley National Wildlife Refuge, we placed remote cameras by four deer gut piles which were wrapped in chicken wire and tethered to trees (visitation piles). Tethered gut piles were monitored for three weeks, then untethered for an additional three weeks. Additionally, we placed four fresh untethered gut piles (persistence piles). Persistence pile duration varied among sites from 1-17 days (mean = 11 days). Wildlife at visitation piles was positively correlated with temperature and we documented 21 species actively feeding on piles, including 6 species of winter resident songbirds. We documented extensive feeding by small mammals (deer mice, squirrels, shrews). While carcasses from visitation piles “disappeared” within 1-2 nights of availability, stomach and intestinal contents were left behind and had active feeding from most species for up to three weeks (including an increase in song bird visitation). We conclude that gut pile persistence on the landscape is highly variable and a large variety of wildlife may have exposure to lead. Additionally, lead contamination from hunter discarded gut piles may be dispersed by small wildlife (such as rodents) and cause secondary poisoning of raptors. Finally, lead from gut piles on the landscape may persist longer than previously thought, providing an extended time frame for exposure of wildlife (including songbirds and small mammals) to lead toxicity.
1:30PM Evaluating the Role of Elk Migration and Weather Variability On the Commingling Risk of Elk and Livestock: Implications for Brucellosis Transmission in Montana
Nathaniel Rayl; Jerod Merkle; Kelly Proffitt; Emily Almberg; Jennifer Jones; Paul Cross
Although the role of migration in the spread and transmission of disease is not well understood, there is evidence that it may either increase or decrease disease prevalence, depending on pathogen traits and host migratory behavior. The onset of elk (Cervus canadensis) migration in the spring coincides with the period of greatest transmission risk for brucellosis (Brucella abortus) in the Greater Yellowstone Ecosystem. Among these elk populations, partial migration is common, with unknown implications for Brucella transmission between elk and cattle. In addition to migration, weather variability (snow depth, spring green-up) also influences the spatiotemporal distribution of elk during the transmission period. Using data from 222 collared female elk from 8 seropositive herds living within the Designated Surveillance Area of Montana, we evaluated the role of migration and weather variability in the risk of seropositive elk shedding and transmitting Brucella to domestic livestock. From our collared sample, we identified migrant and resident elk within herds, and developed resource selection models for these cohorts. Among herds, the onset of migration, the proportion of migratory individuals (range = 0-31%), and the distance of migration (mean = 10-62 km) varied, influencing spatial overlap with cattle. Additionally, patterns of resource selection differed among herds, but there was no clear distinction between selection patterns of resident and migratory elk within herds. We will integrate our resource selection results with herd demographic and brucellosis seroprevalence data, and a model of brucellosis-induced abortion phenology. Together, these data will be used to predict the number of abortions from resident and migratory elk occurring on public and private lands and within livestock allotments during drought, average, and heavy snowfall years. Results from this work can be used to focus disease management efforts on areas with the highest risk of brucellosis transmission in space and time.
1:50PM Climate-Induced Behavioral Changes Influence Exposure of an Arctic Apex Predator to Pathogens and Contaminants
Todd Atwood; Colleen Duncan; Kelly Patyk; Pauline Nol; Jack Rhyan; Matthew McCollum; Melissa McKinney; Andrew Ramey; Jitender Dubey
The use of polar bears (Ursus maritimus) as sentinels of zoonotic disease and contaminants can provide insight into the changing Arctic ecosystem and health risks to other wildlife species and humans. Brucella spp., Coxiella burnetii, Toxoplasma gondii, Francisella tularensis, and Neospora caninum are contagious, and some have been identified in wildlife and humans. Environmental changes to the Arctic marine ecosystem, like reduced sea ice coverage, along with related changes in polar bear behavior (i.e., increased time spent on land) may provide greater opportunities for intra- and inter-species interactions and thus exposure to a greater array of pathogens and contaminants. We assayed serum and plasma samples from the southern Beaufort Sea polar bears to determine the prevalence of Brucella spp., C. burnetii, T. gondii, F. tularensis, and N. caninum and circulating concentrations of persistent organic pollutants (POPs), and evaluated risk factors for exposure. We found the prevalences of Brucella spp. and T. gondii, which had been previously detected in Beaufort Sea polar bears, have increased over time, and also provide the first evidence of exposure of polar bears to C. burnetii, N. caninum, and F. tularensis. We found evidence that climate-induced change in polar bear behavior may influence exposures to certain pathogens and contaminants. Specifically, the odds of exposure to T. gondii were 7 times greater for bears that spent time on land than for bears that remained on the sea ice during summer and fall. For major contaminant classes, mean concentrations of the chlordanes (ΣCHLs), but not other organochlorine pesticides (OCs) nor polychlorinated biphenyls (PCBs), were lower for bears that used terrestrial habitat. Polar bears that come ashore during summer and fall may face altered exposure risks for certain pathogens and contaminants relative to bears that remain on ice year-round.
2:10PM High Seroprevalence of Toxoplasma gondii in Two Large Mammals of the Central Appalachians, USA
John J. Cox; Sean M. Murphy; Brittany Slabach; John T. Hast; Ben C. Augustine; Joseph McDermott; Joseph M. Guthrie; Sutton C. Maehr; Oliver C. H. Kwok; Jitender P. Dubey
Toxoplasma gondii is an important protozoan parasite of mammals that impacts wildlife and human health and behavior. Although this parasite has been documented in several mammalian wildlife species, relatively little is known about T. gondii impacts on North American elk (wapiti, Cervus canadensis) or American black bears (Ursus americanus), both of which have increased in number and expanded range during recent decades. We assessed seroprevalence of T. gondii antibodies using a modified agglutination test (1:25 titer) and blood collected from 142 free-ranging elk and 53 free-ranging black bears in the Central Appalachians, USA, where both species were reintroduced during the 1990s after over a century of absence. Eighty (56.3%) elk were seropositive for T. gondii, with no infection or titer differences between sexes. However, odds of T. gondii infection significantly increased with elk age (β = 0.429, P = 0.001) by a factor of 1.54 (95% CI = 1.19-1.99), and titer increased commensurate with age (JT = 3071, P < 0.001). Thirty-three (62.3%) black bears were seropositive for T. gondii, but we found no infection or titer differences between sexes or among ages for bears. High seroprevalence of T. gondii infection in this region’s two largest mammals may be explained by sympatry with two primary hosts, the bobcat (Lynx rufus) and domestic cat (Felis catus), as well as proximity to human developments and shed oocysts in the soil of this relatively wet and humid region. Because both species are legally harvested annually in the Central Appalachians, we strongly suggest wildlife management agencies incorporate warnings about proper elk and black bear meat preparation into hunter education outreach programs and literature to reduce the chances for human infection from these sources.
2:30PM Prevalence of Toxoplasma gondii, Leptospira spp., and Parvovirus spp. in North American River Otter throughout North Carolina.
Charles W. Sanders; Christopher S. DePerno; Colleen Olfenbuttel
The river otter (Lontra canadensis) is an economically and financially important furbearer in North Carolina. Toxoplasma gondii is a parasite spread largely by cat feces and ingesting infected meat, which causes the disease Toxoplasmosis. Toxoplasmosis is the leading cause of human death attributed to foodborne illness in the United States. Leptospira spp. is a bacterial disease commonly carried by rodents, which causes the disease Leptospirosis. Leptospirosis is highly infectious in most mammal species. Leptospirosis is spread by contact with cuts, abrasions, or ingestion which often results in flu-like symptoms. Parvovirus spp. is a virus that infects individuals in the cat, dog, raccoon, and weasel families. Parvovirus spp. is spread generally through feces, and is acquired either orally or nasally and results in diarrhea, vomiting, and other similar symptoms. All 3 diseases can be fatal to animals and people if untreated. From November 2014 through February 2016, we collected 220 otters from 9 river basins throughout North Carolina and tested them for exposure to T. gondii, Leptospira spp., and Parvovirus spp using Polymerase Chain Reaction (PCR) testing of brain and kidney tissue. We determined that 25% of otters tested positive for T. gondii, 1% tested positive for Leptospira spp., and 19% tested positive for Parvovirus spp.. While our results for Parvovirus spp. seem to be higher than other studies, results for T. gondii and Leptospira were similar or lower than other studies. Knowing the prevalence of these viruses in the natural population provides a baseline to monitor in the future and a glimpse at the health of our waterways now.
2:50PM Refreshment Break
3:20PM Impacts of Exotic Lice on Hair Loss Syndrome Prevalence and Fawn Survival.
Brooke Berger; Greg Gerstenberg; Daniel Barton; Richard N. Brown
Mule deer populations are declining in portions of California, and in Tuolumne County, California mule deer (Odocoileus hemionus californicus) health is of particular concern to managers. Fawns wintering at Jawbone Ridge have been observed with hair loss syndrome (HLS) since 2009 and carry two species of exotic lice that may be linked to the incidence of HLS and mortality. Our goals were to 1) determine the prevalence of exotic lice and HLS in fawns, 2) experimentally test if ectoparasite abundance is associated with incidence of HLS, 3) determine how exotic lice influence fawn survival to the age of recruitment. 126 fawns were captured and marked over three winters, and a subset treated with antiparasitic drugs. During 2010, 2011, and 2012, exotic lice were found on 79 (63%) fawns and 18 (14%) fawns were resighted with HLS. For every unit increase in the ln(ectoparasite abundance), the probability of a fawn developing hair loss increased by a factor of 1.97. None of the recaptured fawns with HLS had lice and HLS was not found to increase mortality. For every unit increase in ln(ectoparasite abundance) fawn mortality probability increased by a factor of 1.3. We conclude that hair loss does not appear to be an immediate threat to fawn survival in the study area and is unlikely to be a primary cause of population declines. However, lice may pose a greater threat than previously thought, and though widespread treatment of deer for lice is impractical, continued monitoring of exotic lice is warranted in this deer herd.
3:40PM Model Recommendations Meet Management Reality: Implementation and Evaluation of a Network-Informed Vaccination Strategy for Endangered Hawaiian Monk Seals
Stacie Robinson; Michelle Barbieri; Jason Baker; Bert Harting; Charles Littnan; Meggan Craft
Infectious agents can threaten the persistence of small populations or vulnerable species. The endangered Hawaiian monk seal (Neomonachus schauinslandi) stands to be heavily impacted by disease threats such as morbillivirus. In 2015 the National Marine Fisheries Service undertook a vaccination program to protect monk seals in the main Hawaiian Islands. We used behavioral observations to construct contact networks which were used to prioritize animals for vaccination based on high connectivity. But the implementation stage of the vaccination program brought logistical constraints and field conditions not accounted for in models. Thus we had a unique opportunity: to test the efficacy of model recommendations applied to reality. We used dynamic network models to simulate morbillivirus outbreaks to evaluate the success of in-field reality compared to idealized vaccinations. We vaccinated a total of 21 on Oahu in 2015. We found that deviating from the ideal did decrease the efficiency of vaccination efforts; 40% more animals had to be vaccinated to achieve a given decrease in outbreak size if animals other than the ideal targets were vaccinated. However, judging by time, we gained protection (decrease in model-derived infection rate) more quickly by vaccinating animals as available rather than waiting for an encounter with a priority seal. This work demonstrates the value of network models in prioritizing vaccination efforts, but also made trade-offs clear: if vaccines were limited, but time was ample, it would be best to wait for the priority animals to achieve greatest herd protection with minimal numbers of vaccines; but if time was more limited than vaccines, it would be better to vaccinate a few more animals and get them done quickly. This work will inform the strategy for on-going efforts to achieve immunity to morbillivirus throughout the Hawaiian monk seal population.
4:00PM Effects of Sylvatic Plague on Northern Idaho Ground Squirrels
Amanda R. Goldberg; Courtney J. Conway; Diane Evans Mack; Greg Burak; Dean E. Biggins
Northern Idaho ground squirrels (Urocitellus brunneus) are a threatened species, but the reason for their decline is not known. Experts believe that the declines were caused by forest encroachment into meadows (habitat loss) due to a century of fire suppression. However, no research has explicitly tested that hypothesis and forest encroachment may not be the reason (or sole reason) for the documented population declines. We sought to test whether sylvatic plague may be responsible (at least in part) for the decline of northern Idaho ground squirrels. We had 2 objectives: (1) Determine whether plague could be responsible for NIDGS population declines, and (2) Determine whether the small mammals that are sympatric with NIDGS are hosts for the same flea species (i.e., whether these species share vectors for plague transmission). We evaluated whether experimental removal of fleas (the vector of plague) increased survival of northern Idaho ground squirrels and 3 coexisting species: Columbian ground squirrels (Urocitellus columbianus), yellow-pine chipmunks (Tamias amoenus), and deer mice (Peromyscus maniculatus). Apparent survival was 1.17, 1.03, and 1.01 times higher on flea removal sites compared to control sites for Columbian ground squirrels, northern Idaho ground squirrels, and chipmunks (respectively). We also used a plague vaccine on chipmunks and deer mice and compared apparent survival between vaccinated animals and control animals on the same plots. Apparent survival of vaccinated animals was 2.78 times higher than that of control animals. We have collected and identified 1,547 fleas from anesthetized animals on our study sites and have documented 6 species of fleas that are known vectors of plague. Both squirrel species and chipmunks share the same suite of flea species. Our results suggest that sylvatic plague is contributing to the decline of the northern Idaho ground squirrel (and is also reducing survival of sympatric species).
4:20PM Spatial Ecology of Gray Foxes: Informing Rabies Management in the Southwest
Amanda M. Veals; John L. Koprowski; Kurt C. VerCauteren; David L. Bergman
Abstract: Space use is a fundamental characteristic of a species that informs our understanding of habitat selection, movement dynamics, and inter- and intraspecific interactions including disease etiology. Gray foxes (Urocyon cinereoargenteus) are considered a substantial reservoir for rabies in the southwestern US; however, little is known about their spatial ecology. We used data acquired from GPS satellite collars on gray foxes in the White Mountains and Pinaleño Mountains of Arizona to compare habitat selection, movement patterns, and home range requirements between a well-connected landscape and an isolated montane ‘sky’ island. In addition, we employed remote wildlife camera traps to assess density and sympatry with other carnivores. We used occupancy modeling and kernel density estimates to compare habitat selection between continuous and isolated forests. Results indicate that gray foxes select for areas of upper evergreen forest mix and Ponderosa Pine (Pinus ponderosa) forest mix. Understanding how foxes as vectors use the landscape is important to control the spread of rabies, and knowledge of gray fox spatial ecology and movement dynamics across an expansive geographic area can better inform disease management plans. In addition to providing valuable information for wildlife disease managers, our results can also inform regional one health strategies.
4:40PM The Importance of Raccoon Movement in Determining the Effectiveness of a Vaccination Barrier Against the Spatial Spread of Raccoon Rabies
Kim M. Pepin; Stacey Elmore; Erin E. Rees; Rich Chipman; Amy T. Gilbert
Animal movement plays a critical role in shaping contact rates and structure, which in turn drive disease dynamics. However, the relationship between host movement behaviors and interventions to disease spread are not well understood. We addressed this gap using a spatial process-based model of raccoon rabies virus transmission. First, we quantified the relationship between realistic distributions of weekly raccoon movement and outcomes of disease dynamics such as persistence, incidence and rates of spatial spread. We demonstrated that these outcomes were very sensitive to only minor increases in the proportion of individuals which moved between 2 and 4 km per week. This high sensitivity to movement also generated substantial differences in the effectiveness of a vaccination barrier. For example, when the proportion of weekly movements > 2 km increased from 5.2% to 6.4%, a 30% higher level of achieved population immunity was required to prevent a rabies breach given conventional vaccination protocols (barrier width of 40 km, vaccine bait drop once per year in the fall). We also examined the relationship between movement distributions and variable vaccination protocols (i.e., width of the barrier, time of the year to drop vaccine bait, frequency of bait drops per year and vaccination coverage) and discussed how an optimal protocol may vary regionally and seasonally depending on underlying raccoon movement distributions.


Contributed Paper
Location: Albuquerque Convention Center Date: September 26, 2017 Time: 1:10 pm - 5:00 pm