Chronic Wasting Disease In Cervids: Prevalence, Impact And Management Strategies

Chronic wasting disease (CWD) is a transmissible spongiform encephalopathy (TSE) that affects members of the cervidae family. The infectious agent is a misfolded isoform (PrPSC) of the host prion protein (PrPC). The replication of PrPSC initiates a cascade of developmental changes that spread from cell to cell, individual to individual, and that for some TSEs, has crossed the species barrier. CWD can be transmitted horizontally and vertically, and it is the only TSE that affects free-ranging wildlife. While other TSEs are under control and even declining, infection rates of CWD continue to grow and the disease distribution continues to expand in North America and around the world. Since the first reported case in 1967, CWD has spread infecting captive and free-ranging cervids in 26 states in the US, 3 Canadian provinces, 3 European countries and has been found in captive cervids in South Korea. CWD causes considerable ecologic, economic and sociologic impact, as this is a 100% fatal highly contagious infectious disease, with no treatment or cure available. Because some TSEs have crossed the species barrier, the zoonotic potential of CWD is a concern for human health and continues to be investigated. Here we review the characteristics of the CWD prion protein, mechanisms of transmission and the role of genetics. We discuss the characteristics that contribute to prevalence and distribution. We also discuss the impact of CWD and review the management strategies that have been used to prevent and control the spread of CWD.https://digitalcommons.snc.edu/faculty_staff_works/1033/thumbnail.jp

Prion protein gene sequence and chronic wasting disease susceptibility in white-tailed deer (Odocoileus virginianus)

The sequence of the prion protein gene (PRNP) affects susceptibility to spongiform encephalopathies, or prion diseases in many species. In white-tailed deer, both coding and non-coding single nucleotide polymorphisms have been identified in this gene that correlate to chronic wasting disease (CWD) susceptibility. Previous studies examined individual nucleotide or amino acid mutations; here we examine all nucleotide polymorphisms and their combined effects on CWD. A 626 bp region of PRNP was examined from 703 free-ranging white-tailed deer. Deer were sampled between 2002 and 2010 by hunter harvest or government culling in Illinois and Wisconsin. Fourteen variable nucleotide positions were identified (4 new and 10 previously reported). We identified 68 diplotypes comprised of 24 predicted haplotypes, with the most common diplotype occurring in 123 individuals. Diplotypes that were found exclusively among positive or negative animals were rare, each occurring in less than 1% of the deer studied. Only one haplotype (C, odds ratio 0.240) and 2 diplotypes (AC and BC, odds ratios of 0.161 and 0.108 respectively) has significant associations with CWD resistance. Each contains mutations (one synonymous nucleotide 555C/T and one nonsynonymous nucleotide 286G/A) at positions reported to be significantly associated with reduced CWD susceptibility. Results suggest that deer populations with higher frequencies of haplotype C or diplotypes AC and BC might have a reduced risk for CWD infection – while populations with lower frequencies may have higher risk for infection. Understanding the genetic basis of CWD has improved our ability to assess herd susceptibility and direct management efforts within CWD infected areas.https://digitalcommons.snc.edu/faculty_staff_works/1029/thumbnail.jp

Influence of landscape factors and management decisions on spatial and temporal patterns of the transmission of chronic wasting disease in white-tailed deer

Abstract. Chronic wasting disease (CWD) has been reported in white-tailed deer at the border of the US states of Illinois and Wisconsin since 2002. Transmission of infectious prions between animals and from the environment has resulted in spatial and temporal structure observable in the spatio-temporal patterns of reported cases. Case locations of 382 positive cases from 28,954 deer tested between 2002 and 2009 provided insight into the potential risk factors and landscape features associated with transmission using a combination of clustering, generalised linear modelling and descriptive evaluations of a risk map of predicted cases of CWD. A species distribution map of white-tailed deer developed using MaxEnt provided an estimate of deer locations. We found that deer probability increased in areas with larger forests and less urban and agricultural lands. Spatial clustering analysis revealed a core area of persistent CWD transmission in the northern part of the region. The regression model indicated that larger and more compact forests were associated with higher risk for CWD. High risk areas also had soils with less clay and more sand than other parts of the region. The transmission potential was higher where landscape features indicated the potential for higher deer concentrations. The inclusion of spatial lag variables improved the model. Of the 102 cases reported in the study area in the two years following the study period, 89 (87%) of those were in the 32% of the study area with the highest 50% of predicted risk of cases

Data from: Survey of haemosporidian parasites in resident and migrant game birds of Illinois

Haemosporidian parasites are globally distributed in avian species, capable of leading to decreased reproductive success, weakness and mortality. Haemosporidian parasites that affect reproduction and population growth are of interest to bird conservation groups and to organizations concerned with the health and immunological status of avian populations. Haemosporidian infection data are not always available for some avian species in specific regions yet. These data provides the starting points to evaluate geographical and temporal changes in the patterns of infection and prevalence across populations. We examined haemoparasite infections in four game bird species commonly hunted in Illinois. Prevalence, mean intensity, median intensity and mean abundance of haemosporidians were calculated, and the relation of these infection measures associated with age and sex of the avian hosts were evaluated. Game species sampled (n = 237) included migrants such as mourning doves (Zenaida macroura), wood ducks (Aix sponsa) and Canada geese (Branta canadensis), as well as resident birds such as wild turkeys (Meleagris gallopavo). Only Haemoproteus, Plasmodium, and Leucocytozoon species were identified. Haemoproteus was the most prevalent haemosporidian (46/237), followed by Plasmodium (11/237). Furthermore, Haemoproteus was the most persistent haemosporidian, as it was the only parasite genera found in all four avian species. Co-infections were found in 55% of turkeys, but no significant correlations between the genera of haemosporidinan co-infections and a host species were found. Moreover, no significant differences in the proportion of infected individuals (prevalence) and haemosporidian quantities (levels of intensity and abundance) were related to biotic factors such as age and sex of the host. However, parasite aggregation (distribution of parasites among hosts) was affected by age, as adult turkeys and juvenile doves showed the highest aggregation index (Poulin’s index of discrepancy D) for Haemoproteus spp. This study reveals patterns of infection and parasite aggregations that vary widely among different game bird species and provides baseline data on avian haemosporidians that, to the best of our knowledge, is not currently available in the state of Illinois for these avian species. Finally, these patterns can be used for management of landscape or host species to support conservation efforts

Food Safety Considerations Related to the Consumption and Handling of Game Meat in North America

Emerging foodborne pathogens present a threat to public health. It is now recognized that several foodborne pathogens originate from wildlife as demonstrated by recent global disease outbreaks. Zoonotic spillover events are closely related to the ubiquity of parasitic, bacterial, and viral pathogens present within human and animal populations and their surrounding environment. Foodborne diseases have economic and international trade impacts, incentivizing effective wildlife disease management. In North America, there are no food safety standards for handling and consumption of free-ranging game meat. Game meat consumption continues to rise in North America; however, this growing practice could place recreational hunters and game meat consumers at increased risk of foodborne diseases. Recreational hunters should follow effective game meat food hygiene practices from harvest to storage and consumption. Here, we provide a synthesis review that evaluates the ecological and epidemiological drivers of foodborne disease risk in North American hunter populations that are associated with the harvest and consumption of terrestrial mammal game meat. We anticipate this work could serve as a foundation of preventive measures that mitigate foodborne disease transmission between free-ranging mammalian and human populations

The impact of maternal infection with chronic wasting disease on fetal characteristics in wild white-tailed deer (Odocoileus virginianus) in Illinois, USA

abstract: Chronic wasting disease (CWD) is a fatal neurodegenerative disease of cervids caused by a misfolded and infectious protein, called a prion. Infection with CWD is characterized by an asymptomatic period, followed by a decline that inevitably leads to death. The disease is transmitted mainly through direct contact between infected and uninfected animals, but vertical transmission has been documented in muntjac deer (Muntiacus reevesi), along with the presence of infectious prions in the reproductive tissues of elk (Cervus canadensis) and white-tailed deer (Odocoileus virginianus). Therefore, questions have been raised about the effects of CWD on the health and characteristics of the offspring gestated by infected animals, and about how vertical transmission may complicate disease management efforts and drive reduction of herd fitness. To begin finding quantitative answers to these questions, this study used multilevel Bayesian linear regression to model the influence of maternal infection with CWD, along with several other environmental and biological variables, on fetal weight, sex, and length using data collected on white-tailed deer as part of the CWD management program in Illinois for the time period between fiscal years 2003 and 2020. The regression analyses found no statistically significant relationship between maternal CWD status and fetal length or the fraction of males in a litter but did find a significant relationship between maternal infection and fetal weight. Fetuses of CWD positive deer weighed 1% less than fetuses from deer in which CWD was not detected. Given that 88% of the fetuses in this data were in the second trimester of gestation, the impact of CWD on fetuses through the entire course of gestation remains to be evaluated

Trash to treasure: assessing viability of wing biopsies for use in bat genetic research

The outbreak of white-nose syndrome in North American bats has resulted in massive data collection efforts to characterize the fungus, Pseudogymnoascus destructans. Wing biopsies routinely are collected from live bats, placed in agar media to culture the fungus, and ultimately discarded. We tested whether these discarded tissues represent a viable source of host bat DNA. We found no difference in DNA concentration and no reduction of DNA quality between samples that were extracted immediately compared to samples placed in agar for fungal culture. Although recovered quantities were low, concentrations increased using a cleanup kit. Our study suggests samples collected from live bats can be leveraged across disciplines to further our understanding of bat genetics and the impact of white-nose syndrome

Trash to treasure: assessing viability of wing biopsies for use in bat genetic research

The outbreak of white-nose syndrome in North American bats has resulted in massive data collection efforts to characterize the fungus, Pseudogymnoascus destructans. Wing biopsies routinely are collected from live bats, placed in agar media to culture the fungus, and ultimately discarded. We tested whether these discarded tissues represent a viable source of host bat DNA. We found no difference in DNA concentration and no reduction of DNA quality between samples that were extracted immediately compared to samples placed in agar for fungal culture. Although recovered quantities were low, concentrations increased using a cleanup kit. Our study suggests samples collected from live bats can be leveraged across disciplines to further our understanding of bat genetics and the impact of white-nose syndrome

Data file of sex, age and number of haemosporidians identified in game birds of Illinois

Data file of sex, age and number of haemosporidians identified in game birds of Illinoi

Influence of the geographic distribution of prion protein gene sequence variation on patterns of chronic wasting disease spread in white-tailed deer (Odocoileus virginianus)

Managing and controlling the spread of diseases in wild animal populations is challenging, especially for highly social and mobile species. Effective management would benefit from information about disease susceptibility, allowing limited resources to be focused on areas or populations with a higher risk of infection. Chronic wasting disease (CWD), a transmissible spongiform encephalopathy that affects cervids, was first detected in Colorado. In 2002 CWD was detected in Illinois and Wisconsin and has since spread through many counties. Specific nucleotide variations in the prion protein gene (PRNP) sequence have been associated with reduced susceptibility to CWD in white-tailed deer. Though genetic resistance is incomplete, the frequency of deer possessing these mutations in a population is an important factor in disease spread (i.e. herd immunity). In this study we sequenced 625 bp of the PRNP gene from a sampling of 2433 deer from Illinois and Wisconsin. In north-central Illinois where CWD was first detected, counties had a low frequency of protective haplotypes (frequency \u3c 0.20); whereas in northwestern Illinois counties, where CWD cases have only more recently been detected, the frequency of protective haplotypes (frequency \u3e 0.30) was much higher (p \u3c 0.05). Protective haplotype frequencies varied significantly among infected and uninfected geographic areas. The frequency of protective PRNP haplotypes may contribute to population level susceptibility and may shape the way CWD has spread through Illinois. Analysis of PRNP haplotype distribution could be a powerful tool to assess CWD risk and best allocate resources to contain and reduce the spread of infection