Gray wolf mortality patterns in Wisconsin from 1979 to 2012.

Starting in the 1970s, many populations of large-bodied mammalian carnivores began to recover from centuries of human-caused eradication and habitat destruction. The recovery of several such populations has since slowed or reversed due to mortality caused by humans. Illegal killing (poaching) is a primary cause of death in many carnivore populations. Law enforcement agencies face difficulties in preventing poaching and scientists face challenges in measuring it. Both challenges are exacerbated when evidence is concealed or ignored. We present data on deaths of 937 Wisconsin gray wolves (Canis lupus) from October 1979 to April 2012 during a period in which wolves were recolonizing historic range mainly under federal government protection. We found and partially remedied sampling and measurement biases in the source data by reexamining necropsy reports and reconstructing the numbers and causes of some wolf deaths that were never reported. From 431 deaths and disappearances of radiocollared wolves aged > 7.5 months, we estimated human causes accounted for two-thirds of reported and reconstructed deaths, including poaching in 39-45%, vehicle collisions in 13%, legal killing by state agents in 6%, and nonhuman causes in 36-42%. Our estimate of poaching remained an underestimate because of persistent sources of uncertainty and systematic underreporting. Unreported deaths accounted for over two-thirds of all mortality annually among wolves > 7.5 months old. One-half of all poached wolves went unreported, or > 80% of poached wolves not being monitored by radiotelemetry went unreported. The annual mortality rate averaged 18% ± 10% for monitored wolves but 47% ± 19% for unmonitored wolves. That difference appeared to be due largely to radiocollaring being concentrated in the core areas of wolf range, as well as higher rates of human-caused mortality in the periphery of wolf range. We detected an average 4% decline in wolf population growth in the last 5 years of the study. Because our estimates of poaching risk and overall mortality rate exceeded official estimates after 2012, we present all data for transparency and replication. More recent additions of public hunting quotas after 2012 appear unsustainable without effective curtailment of poaching. Effective antipoaching enforcement will require more accurate estimates of poaching rate, location, and timing than currently available. Independent scientific review of methods and data will improve antipoaching policies for large carnivore conservation, especially for controversial species facing high levels of human-induced mortality.

Acute pasteurellosis in wild big brown bats (Eptesicus fuscus).

We report acute fatal pasteurellosis in wild big brown bats (Eptesicus fuscus) in Wisconsin, USA. Mortality of approximately 100 bats was documented over 4 wk, with no evidence for predatory injuries. Pasteurella multocida serotype 1 was isolated from multiple internal organs from four of five bats examined postmortem.

Chronic wasting disease (CWD) susceptibility of several North American rodents that are sympatric with cervid CWD epidemics.

Chronic wasting disease (CWD) is a highly contagious always fatal neurodegenerative disease that is currently known to naturally infect only species of the deer family, Cervidae. CWD epidemics are occurring in free-ranging cervids at several locations in North America, and other wildlife species are certainly being exposed to infectious material. To assess the potential for transmission, we intracerebrally inoculated four species of epidemic-sympatric rodents with CWD. Transmission was efficient in all species; the onset of disease was faster in the two vole species than the two Peromyscus spp. The results for inocula prepared from CWD-positive deer with or without CWD-resistant genotypes were similar. Survival times were substantially shortened upon second passage, demonstrating adaptation. Unlike all other known prion protein sequences for cricetid rodents that possess asparagine at position 170, our red-backed voles expressed serine and refute previous suggestions that a serine in this position substantially reduces susceptibility to CWD. Given the scavenging habits of these rodent species, the apparent persistence of CWD prions in the environment, and the inevitable exposure of these rodents to CWD prions, our intracerebral challenge results indicate that further investigation of the possibility of natural transmission is warranted.

Surveillance to detect chronic wasting disease in white-tailed deer in Wisconsin.

Chronic wasting disease (CWD), a prion disease affecting North American cervids, has been discovered in at least 12 states and provinces throughout the continent. Since 2002, a number of states and provinces have initiated surveillance programs to detect CWD in native cervid populations. However, many questions remain about the appropriate methods, geographic scope, and number of samples required for an effective CWD surveillance program. We provide an improved statistical method to calculate the probability of detecting CWD in primary sample units (e.g., county or deer management unit) that also considers deer abundance and the nonrandom distribution of CWD and hunter harvests. We used this method to analyze data from a statewide CWD detection program conducted in Wisconsin during the autumns of 2002 and 2003 to determine the distribution of CWD in white-tailed deer (Odocoileus virginianus). Deer heads were collected at hunter registration stations, and brainstem (obex) and retropharyngeal lymph nodes were removed for disease testing. Our analysis includes samples from >35,000 deer collected outside the known affected area. The probability of detecting chronic wasting disease at a prevalence of 1% varied from 0.89 to > or =0.99 among the 56 primary sample units. Detection probabilities for 1% CWD prevalence were >0.9 in 55 primary sample units, and >0.99 in 10. Detection probabilities will be higher in areas where CWD prevalence exceeds 1%. CWD-positive deer were detected in eight primary sample units surrounding the known affected area during surveillance activities. Our approach provides a novel statistical technique to accommodate nonrandom sampling in wildlife disease surveillance programs.

Distribution of antibodies reactive to Borrelia lonestari and Borrelia burgdorferi in white-tailed deer (Odocoileus virginianus) populations in the eastern United States.

Southern tick-associated rash illness is a Lyme-like syndrome that occurs in the southern states. Borrelia lonestari, which has been suggested as a possible causative agent of southern tick-associated rash illness, naturally infects white-tailed deer (WTD; Odocoileus virginianus) and is transmitted by the lone star tick (Amblyomma americanum). To better understand the prevalence and distribution of Borrelia exposure among WTD, we tested WTD from 21 eastern states for antibodies reactive to B. lonestari using an indirect immunofluorescent antibody assay and Borrelia burgdorferi using the IDEXX SNAP 4Dx test. A total of 107/714 (15%) had antibodies reactive to B. lonestari, and prevalence of antibodies was higher in deer from southern states (17.5%) than in deer from northern states (9.2%). Using the SNAP 4DX test, we found that 73/723 (10%) were positive for B. burgdorferi, and significantly more northern deer (23.9%) were positive compared with southern deer (3.8%). Our data demonstrate that WTD are exposed to both Borrelia species, but antibody prevalence for exposure to the two species differs regionally and distributions correlate with the presence of Ixodes scapularis and A. americanum ticks.

Genetic susceptibility to chronic wasting disease in free-ranging white-tailed deer: complement component C1q and Prnp polymorphisms.

The genetic basis of susceptibility to chronic wasting disease (CWD) in free-ranging cervids is of great interest. Association studies of disease susceptibility in free-ranging populations, however, face considerable challenges including: the need for large sample sizes when disease is rare, animals of unknown pedigree create a risk of spurious results due to population admixture, and the inability to control disease exposure or dose. We used an innovative matched case-control design and conditional logistic regression to evaluate associations between polymorphisms of complement C1q and prion protein (Prnp) genes and CWD infection in white-tailed deer from the CWD endemic area in south-central Wisconsin. To reduce problems due to admixture or disease-risk confounding, we used neutral genetic (microsatellite) data to identify closely related CWD-positive (n=68) and CWD-negative (n=91) female deer to serve as matched cases and controls. Cases and controls were also matched on factors (sex, location, age) previously demonstrated to affect CWD infection risk. For Prnp, deer with at least one Serine (S) at amino acid 96 were significantly less likely to be CWD-positive relative to deer homozygous for Glycine (G). This is the first characterization of genes associated with the complement system in white-tailed deer. No tests for association between any C1q polymorphism and CWD infection were significant at p<0.05. After controlling for Prnp, we found weak support for an elevated risk of CWD infection in deer with at least one Glycine (G) at amino acid 56 of the C1qC gene. While we documented numerous amino acid polymorphisms in C1q genes none appear to be strongly associated with CWD susceptibility.

Infectious prions in pre-clinical deer and transmission of chronic wasting disease solely by environmental exposure.

Key to understanding the epidemiology and pathogenesis of prion diseases, including chronic wasting disease (CWD) of cervids, is determining the mode of transmission from one individual to another. We have previously reported that saliva and blood from CWD-infected deer contain sufficient infectious prions to transmit disease upon passage into naïve deer. Here we again use bioassays in deer to show that blood and saliva of pre-symptomatic deer contain infectious prions capable of infecting naïve deer and that naïve deer exposed only to environmental fomites from the suites of CWD-infected deer acquired CWD infection after a period of 15 months post initial exposure. These results help to further explain the basis for the facile transmission of CWD, highlight the complexities associated with CWD transmission among cervids in their natural environment, emphasize the potential utility of blood-based testing to detect pre-clinical CWD infection, and could augur similar transmission dynamics in other prion infections.

Landscape genetics and the spatial distribution of chronic wasting disease.

Predicting the spread of wildlife disease is critical for identifying populations at risk, targeting surveillance and designing proactive management programmes. We used a landscape genetics approach to identify landscape features that influenced gene flow and the distribution of chronic wasting disease (CWD) in Wisconsin white-tailed deer. CWD prevalence was negatively correlated with genetic differentiation of study area deer from deer in the area of disease origin (core-area). Genetic differentiation was greatest, and CWD prevalence lowest, in areas separated from the core-area by the Wisconsin River, indicating that this river reduced deer gene flow and probably disease spread. Features of the landscape that influence host dispersal and spatial patterns of disease can be identified based on host spatial genetic structure. Landscape genetics may be used to predict high-risk populations based on their genetic connection to infected populations and to target disease surveillance, control and preventative activities.

Spatial epidemiology of chronic wasting disease in Wisconsin white-tailed deer.

Chronic wasting disease (CWD) is a fatal, emerging disease of cervids associated with transmissible protease-resistant prion proteins. The potential for CWD to cause dramatic declines in deer and elk populations and perceived human health risks associated with consuming CWD-contaminated venison have led wildlife agencies to embark on extensive CWD control programs, typically involving culling to reduce deer populations. We characterized the spatial distribution of CWD in white-tailed deer (Odocoileus virginianus) in Wisconsin to facilitate CWD management. We found that CWD prevalence declined with distance from a central location, was locally correlated at a scale of 3.6 km, and was correlated with deer habitat abundance. The latter result is consistent with patterns expected for a positive relationship between density and prevalence of CWD. We recommend management activities focused on culling in geographic areas with high prevalence to have the greatest probability of removing infected individuals. Further research is needed to elucidate the factors involved in CWD spread and infection rates, especially the role of density-dependent transmission.

Levels of fecal corticosterone in sandhill cranes during a human-led migration.

Fourteen captive-reared greater sandhill cranes (Grus canadensis tabida) were conditioned to follow ultralight aircraft to promote migration between Wisconsin and Florida (USA) after release. Fecal samples were collected throughout the training period in Wisconsin and during a l977-km human-led migration to Florida to determine fecal corticosterone (FC) concentrations by radioimmunnoassay. The mean (+/-SE) FC concentration during the training period was 109.5 +/- 7.5 ng/g and was representative of baseline levels recorded previously from sandhill cranes. Fecal corticosterone concentrations increased in early migration compared to concentrations I mo prior to departure (P < 0.01) but were not different from baseline concentrations at tile end of the 6-wk migration period. The variability of FC concentrations in individual samples was greater throughout the migration than the training period. Increases in FC during migration were modest and generally consistent with normal corticosterone elevations observed in migrating birds.

Ultrasonographic imaging of the sandhill crane (Grus canadensis) intertarsal joint.

Tendon ossification in the crus and tarsometatarsal regions of cranes makes ultrasonography difficult everywhere except for joints, where ossification is absent. Normal ultrasonographic anatomy of the adult Florida sandhill crane (Grus canadensis pratensis) intertarsal joint is described on the basis of ultrasonography that was performed on the limbs of a cadaver, which were dissected and cross-sectioned subsequently, to correlate ultrasonographic images with anatomic structures. Intertarsal joints of five normal sandhill cranes and two cranes with known intertarsal abnormalities were then imaged bilaterally in transverse and sagittal planes. Ultrasonographic imaging can be used to evaluate the soft-tissue structures on the dorsal and plantar aspects of the intertarsal joint of cranes, and it is a useful adjunct to physical and radiographic examination for localizing injuries to this area.