Detection of CWD Prions in Urine and Saliva of Deer by Transgenic Mouse Bioassay

Abstract

Chronic wasting disease (CWD) is a prion disease affecting captive and free-ranging cervids (e.g. deer, elk, and moose). The mechanisms of CWD transmission are poorly understood, though bodily fluids are thought to play an important role. Here we report the presence of infectious prions in the urine and saliva of deer with chronic wasting disease (CWD). Prion infectivity was detected by bioassay of concentrated, dialyzed urine and saliva in transgenic mice expressing the cervid PrP gene (Tg[CerPrP] mice). In addition, PrPCWD was detected in pooled and concentrated urine by protein misfolding cyclic amplification (PMCA). The concentration of abnormal prion protein in bodily fluids was very low, as indicated by: undetectable PrPCWD levels by traditional assays (western blot, ELISA) and prolonged incubation periods and incomplete TSE attack rates in inoculated Tg(CerPrP) mice (373±3days in 2 of 9 urine-inoculated mice and 342±109 days in 8 of 9 saliva-inoculated mice). These findings help extend our understanding of CWD prion shedding and transmission and portend the detection of infectious prions in body fluids in other prion infections.

Prion transmission

“…Indeed, deer with clinical CWD and mild to moderate nephritis produced urine containing sPMCA-detectable PrP Sc and CWD-infectivity. 41 Overall, data demonstrates the secretion of prion within the urine of animals in the terminal stages of prion disease at levels 10-fold lower 38 or similar to 37 that found in plasma; the latter estimated to be approximately 0.5-5 fg/ml of PrP Sc . 38 While not a prerequisite for prionuria, nephritis may well lead to the increased secretion of prion within urine.…”

“…70 The amounts of prion present in saliva are likely to be low as indicated by CWD-infected saliva producing prolonged incubation periods and incomplete attack rates within the transgenic mouse bioassay. 41 …”

Pathogenesis of Chronic Wasting Disease in Cervidized Transgenic Mice

“…79,80 The vehicle responsible for the spread of prions between cage-mates is uncertain, but other studies in cervids and rodent model systems support the plausibility of biological fluids and excreta as transmission vehicles. 48,81,82 Given the presence of PrP RES in the taste buds of inoculated Tg[CerPrP] mice, horizontal spread could be linked to the shedding of prion-infected cells into oronasal secretions. 71 In addition to direct animal-to-animal contact or animal-to-excreta contact, coprophagy is also plausible, as evidenced by the transmission of CWD and scrapie by exposure of naive animals to a contaminated environment.…”

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

“…Blood, saliva, urine and faeces of infected animals are potential sources of CWD infection within a herd (Sigurdson et al, 1999;Mathiason et al, 2006;Haley et al, 2009;Tamgüney et al, 2009). Additional laboratory evidence demonstrated that both skeletal muscle and central nervous system tissues are important sources of prions that can result in CWD (Angers et al, 2006).…”

“…Prions in urine, faecal material or from an infected carcass can enter the environment and remain infectious for long periods Haley et al, 2009;Saunders et al, 2012). Prions bind strongly to various types of soil and resist removal by water or various solvents (Leita et al, 2006;Saunders et al, 2008) so though possibly long-lasting, there is little subsequent migration or leaching through the soil (Jacobson et al, 2010;Maddison et al, 2010).…”