Dietary magnesium and copper affect survival time and neuroinflammation in chronic wasting disease

Detection of two dissimilar chronic wasting disease isolates in two captive Rocky Mountain elk (Cervus canadensis) herds

Chronic wasting disease (CWD) continues to spread in both wild and captive cervid herds in North America and has now been identified in wild reindeer and moose in Norway, Finland and Sweden. There is limited knowledge about the variety and characteristics of isolates or strains of CWD that exist in the landscape and their implications on wild and captive cervid herds. In this study, we evaluated brain samples from two captive elk herds that had differing prevalence, history and timelines of CWD incidence. Site 1 had a 16-year history of CWD with a consistently low prevalence between 5% and 10%. Twelve of fourteen naïve animals placed on the site remained CWD negative after 5 years of residence. Site 2 herd had a nearly 40-year known history of CWD with long-term environmental accrual of prion leading to nearly 100% of naïve animals developing clinical CWD within two to 12 years. Obex samples of several elk from each site were compared for CWD prion strain deposition, genotype in prion protein gene codon 132, and conformational stability of CWD prions. CWD prions in the obex from site 2 had a lower conformational stability than those from site 1, which was independent of prnp genotype at codon 132. These findings suggest the existence of different CWD isolates between the two sites and suggest potential differential disease attack rates for different CWD strains.

EFFECT OF ORAL COPPER SUPPLEMENTATION ON SUSCEPTIBILITY IN WHITE-TAILED DEER (ODOCOILEUS VIRGINIANUS) TO CHRONIC WASTING DISEASE

Chronic wasting disease (CWD) is an infectious disease, but reported associations suggest several metals-especially copper (Cu) and manganese-potentially play a role in this and other prion diseases. To assess the utility of dietary Cu supplementation in protecting white-tailed deer (Odocoileus virginianus) from CWD, we compared incidence and disease course among individuals naturally exposed to CWD while being maintained on sustained-release Cu boluses or unsupplemented (control). Oral Cu supplementation increased liver tissue Cu concentrations compared to controls but did not affect susceptibility to CWD or survival after natural exposure in the captive white-tailed deer we studied. Over the 27 mo study, 89% (8/9) of the Cu-supplemented deer and 86% (6/7) of control deer became CWD-infected. Survival to 27 mo postexposure did not differ between Cu-supplemented and control deer: model-averaged survival probabilities to 27 mo were 0.45-0.47 for all combinations of Cu treatment and PRNP gene haplotype presence. The PRNP gene haplotype influenced the probability of deer remaining biopsy negative for at least 17 mo but did not affect overall susceptibility.

Pig slurry needs modifications to be a sustainable fertilizer in crop production

Pig slurry from modern high-technological farms contain copper and zinc, which is under suspicion of being co-factors in the development of antibiotic resistance. In addition, these two elements contaminate the surrounding environment when spread in large quantities. Therefore, biogas plants and biomembranes should be used to remove hazardous substances such as copper, zink, antibiotics and antibiotic resistant bacteria before pig slurry is used as a fertilizer in crop production. That would allow recycling of phosphorous in a way that only to a limited extent affect the health of the environment.

Copper signalling: causes and consequences

Copper-containing enzymes perform fundamental functions by activating dioxygen (O2) and therefore allowing chemical energy-transfer for aerobic metabolism. The copper-dependence of O2 transport, metabolism and production of signalling molecules are supported by molecular systems that regulate and preserve tightly-bound static and weakly-bound dynamic cellular copper pools. Disruption of the reducing intracellular environment, characterized by glutathione shortage and ambient Cu(II) abundance drives oxidative stress and interferes with the bidirectional, copper-dependent communication between neurons and astrocytes, eventually leading to various brain disease forms. A deeper understanding of of the regulatory effects of copper on neuro-glia coupling via polyamine metabolism may reveal novel copper signalling functions and new directions for therapeutic intervention in brain disorders associated with aberrant copper metabolism.

Differential effects of divalent cations on elk prion protein fibril formation and stability

Misfolding of the normally folded prion protein of mammals (PrP^C) into infectious fibrils causes a variety of diseases, from scrapie in sheep to chronic wasting disease (CWD) in cervids. The misfolded form of PrP^C, termed PrP^Sc, or in this case PrP^CWD, interacts with PrP^C to create more PrP^CWD. This process is not clearly defined but is affected by the presence and interactions of biotic and abiotic cofactors. These include nucleic acids, lipids, glycosylation, pH, and ionic character. PrP^C has been shown to act as a copper-binding protein in vivo, though it also binds to other divalents as well. The significance of this action has not been conclusively elucidated. Previous reports have shown that metal binding sites occur throughout the N-terminal region of PrP^C. Other cations like manganese have also been shown to affect PrP^C abundance in a transcript-independent fashion. Here, we examined the ability of different divalent cations to influence the stability and in vitro conversion of two variants of PrP from elk (L/M132, 26-234). We find that copper and zinc de-stabilize PrP. We also find that PrP M132 exhibits a greater degree of divalent cation induced destabilization than L132. This supports findings that leucine at position 132 confers resistance to CWD, while M132 is susceptible. However, in vitro conversion of PrP is equally suppressed by either copper or zinc, in both L132 and M132 backgrounds. This report demonstrates the complex importance of ionic character on the PrP^C folding pathway selection on the route to PrP^Sc formation.

Detection of Prions in Blood of Cervids at the Asymptomatic Stage of Chronic Wasting Disease

Chronic wasting disease (CWD) is a rapidly spreading prion disorder affecting captive and free-ranging cervids. The zoonotic potential of CWD is unknown, as well as the mechanism for its highly efficient transmission. A top priority to minimize further spreading of this disease and its potential impact on environmental prion contamination is the development of a non-invasive, sensitive, and specific test for ante-mortem detection of infected animals. Here, we optimized the protein misfolding cyclic amplification (PMCA) assay for highly efficient detection of CWD prions in blood samples. Studies were done using a blind panel of 98 field-collected samples of whole blood from codon 96 glycine/glycine, captive white-tailed deer that were analyzed for prion infection post-mortem by immunohistochemistry (IHC). The results showed a sensitivity of 100% in animals with very poor body condition that were IHC-positive in both brain and lymph nodes, 96% in asymptomatic deer IHC-positive in brain and lymph nodes and 53% in animals at early stages of infection that were IHC-positive only in lymph nodes. The overall mean diagnostic sensitivity was 79.3% with 100% specificity. These findings show that PMCA might be useful as a blood test for routine, live animal diagnosis of CWD.

Trace elements in unconventional animals: A 40-year experience

The role of trace elements in animal health has attracted increasing interest in recent years. The essentiality and toxicity of these elements have been extensively investigated in humans, laboratory animal models and partially in domestic animals, whereas little is known about trace element metabolism in most living organisms. Forty years ago our research started on Cd metabolism in molluscs, thereafter expanding to Zn, Cu, and Fe metabolism in many unconventional animal species of veterinary interest. This review summarizes the main results obtained over this long period of time: some of the findings are original and have not been published to date. They are discussed in more detail and compared with data obtained in conventional animals, including man.