Temporal patterns of chronic wasting disease prion excretion in three cervid species

Abstract

Chronic wasting disease (CWD) is the only naturally occurring transmissible spongiform encephalopathy affecting free-ranging wildlife populations. Transmission of CWD occurs by direct contact or through contaminated environments; however, little is known about the temporal patterns of CWD prion excretion and shedding in wild cervids. We tested the urine and faeces of three species of captive cervids (elk, mule and white-tailed deer) at 6, 12, 18 and 24 months after oral inoculation to evaluate the temporal, species- and genotype-specific factors affecting the excretion of CWD prions. Although none of the animals exhibited clinical signs of CWD during the study, we determined that all three cervid species were excreting CWD prions by 6 months post-inoculation. Faecal samples were consistently positive for CWD prions for all three cervid species (88 %), and were more likely to be positive than urine samples (28 %). Cervids with genotypes encoding for the prion protein (PRNP) that were considered to be more susceptible to CWD were more likely to excrete CWD prions (94 %) than cervids with genotypes considered to be less susceptible (64 %). All cervids with CWD prions in their urine also had positive faeces (n=5), but the converse was not true. Our study is the first to demonstrate CWD prion excretion in urine by asymptomatic elk and mule deer. Our results indicate that the excretion of CWD prions in faeces and, to a lesser extent, urine may provide an important avenue for depositing prions in the environment.

The ecology of chronic wasting disease in wildlife

“…After infection, incubation period in wild cervids is generally between 2 and 4 years with a minimum of 16 months before development of symptoms (Williams, ). During the pre‐clinical, asymptomatic phase, prions can be detected in faeces, urine, and saliva as early as 6 months post‐infection (Plummer et al ., ). Symptoms associated with late‐stage CWD infection include emaciation, excessive salivation, behavioural changes, ataxia, depression, and weakness (Williams & Young, ; Spraker et al ., ).…”

“…During the pre-clinical, asymptomatic phase, prions can be detected in faeces, urine, and saliva as early as 6 months post-infection (Plummer et al, 2017). Symptoms associated with late-stage CWD infection include emaciation, excessive salivation, behavioural changes, ataxia, depression, and weakness (Williams & Young, 1980;Spraker et al, 1997).…”

“…Experimental studies have shown that infectious prions can enter the environment through saliva, faeces, urine, blood, antler velvet, or placenta tissue from infected animals, and carcasses (Angers et al, 2009;Zabel & Ortega, 2017). Importantly, CWD contamination of the environment via prion shedding in cervid excreta occurs many months before the onset of clinical disease Plummer et al, 2017). Prions are hardy in the environment, are resistant to most general disinfectants (e.g.…”

Update on chronic wasting disease (CWD) III

“…In animals incubating CWD, abnormal PrP and/or infectivity has been demonstrated in placenta, saliva, faeces and urine which are all likely to contribute to inter-individual transmission but also to the general contamination of the environment (Mathiason et al, 2006;Tamguney et al, 2009a;Haley and Hoover, 2015;Plummer et al, 2017).…”

Estimating relative CWD susceptibility and disease progression in farmed whitetail deer with rare PRNP alleles

“…and while there are several limited reports of CWD prion shedding in more common whitetail deer 280 genotypes (11,23,51), the biological relevance of prions likely shed in biological fluids has proven more 281 difficult to assess. (16,38,39) The lifespan of the host is also relevant when considering incubation periods 282 of the disease -particularly in farmed deer, where age may be useful as a selective management factor, 283 similar to strategies used to address concerns for zoonotic transmission of BSE from cattle.…”