Chronic Wasting Disease

Abstract

Abstract. Chronic wasting disease (CWD) is a unique transmissible spongiform encephalopathy (TSE) of mule deer (Odocoileus hemionus), white-tailed deer (O. virginianus), and Rocky Mountain elk (Cervus elaphus nelsoni). The natural history of CWD is incompletely understood, but it differs from scrapie and bovine spongiform encephalopathy (BSE) by virtue of its occurrence in nondomestic and free-ranging species. CWD has many features in common with scrapie, including early widespread distribution of disease-associated prion protein (PrP d ) in lymphoid tissues, with later involvement of central nervous system (CNS) and peripheral tissues. This distribution likely contributes to apparent efficiency of horizontal transmission and, in this, is similar to scrapie and differs from BSE. Clinical features and lesions of CWD are qualitatively similar to the other animal TSEs. Microscopically, marked spongiform lesions occur in the central nervous system (CNS) after a prolonged incubation period and variable course of clinical disease. During incubation, PrP d can be identified in tissues by antibody-based detection systems. Although CWD can be transmitted by intracerebral inoculation to cattle, sheep, and goats, ongoing studies have not demonstrated that domestic livestock are susceptible via oral exposure, the presumed natural route of exposure to TSEs. Surveillance efforts for CWD in captive and free-ranging cervids will continue in concert with similar activities for scrapie and BSE. Eradication of CWD in farmed cervids is the goal of state, federal, and industry programs, but eradication of CWD from free-ranging populations of cervids is unlikely with currently available management techniques.Key words: Chronic wasting disease; elk; mule deer; prion disease; transmissible spongiform encephalopathy; white-tailed deer.The transmissible spongiform encephalopathies (TSEs) are unusual infectious diseases of animals and humans. The TSEs, including chronic wasting disease (CWD), are designated prion diseases because of their association with aberrantly refolded isoforms of the prion protein, a normal cellular glycoprotein (PrP C ). 120 CWD-associated prion protein (PrP CWD or PrP d ) 82 is widespread in the lymphoid tissues and the CNS from early in the incubation phase until death. 98,132,137 Scrapie, the first TSE identified, was the focus of considerable research and even controversy concerning its origin and nature (genetic versus infectious) for many years. 2,114,115 However, it was the recognition that prion diseases were transmissible and affected humans as well as animals that stimulated much of the current scientific interest in the nature of these diseases.Scrapie has been recognized for hundreds of years, transmissible mink encephalopathy (TME) for more than 50 years, CWD for more than 30 years, and bovine spongiform encephalopathy (BSE) for fewer than 20 years. Although CWD is now well known, it was just a few years ago considered an obscure disease of mule deer (Odocoileus hemionus) and elk (Cervus elaphus nelso...

A Natural Case of Chronic Wasting Disease in a Free-ranging Moose (Alces alces shirasi)

“…In addition to the DMNV, IHC revealed chromagen deposits indicative of PrP CWD accumulation in the solitarius, cuneate, reticular, and hypoglossal nuclei as well as the nucleus ambiguus and the nucleus of the spinal tract of the trigeminal nerve. With the exception of intraneuronal chromagen deposition being somewhat more common in this case, the patterns observed were virtually indistinguishable from those described previously in cases of CWD in deer and wapiti (Spraker et al, 1997(Spraker et al, , 2002aMiller and Williams, 2002;Williams, 2005) and in a moose experimentally infected with CWD (Kreeger et al, 2006).…”

“…Chronic wasting disease occurs naturally in both deer and wapiti, but it has not been reported to occur naturally in other North American cervid species. Because of their close taxonomic relationship and similarities in DNA sequences of the prion protein (PrP) coding region to deer and wapiti, it had been hypothesized that moose (Alces alces shirasi) would be naturally susceptible to infection if sufficient exposure to the CWD agent occurred (Williams, 2005). A recent experiment using oral exposure to infectious brain tissue in captive moose confirmed that this species is susceptible to CWD (Kreeger et al, 2006).…”

“…The mid raphe also showed vacuolization in the white matter. These spongiform changes were typical of lesions seen in deer and wapiti with CWD (Williams and Young, 1993;Spraker et al, 1997Spraker et al, , 2002aWilliams, 2005). Fresh palatine tonsil and RPLN extracts were analyzed by Western immunoblot (WB) by using established methods (Kreeger et al, 2006) as an independent assessment of CWD infection.…”

A prion disease of cervids: Chronic wasting disease

“…Isolated, noncontinguous clusters of prion-infected cervids have been located as far west as Utah and extending east to New York and West Virginia 1 . Local prevalences have reached as high as 30% of free-ranging deer [93]. In Canada, CWD cases have been diagnosed in farmed elk and white-tailed deer, as well as free-ranging deer in Saskatchewan and Alberta [39,87].…”

Wasting and Neurologic Signs in a White-tailed Deer (Odocoileus virginianus) not Associated with Abnormal Prion Protein

“…Chronic wasting disease (CWD) is a fatal, neurodegenerative transmissible spongiform encephalopathy (TSE) that has been identified in captive and freeranging cervids (Williams, 2005). To our knowledge, neither nonprion-associated spongiform change nor mineralization of blood vessels in the brain has been previously reported in white-tailed deer (Odocoileus virginianus).…”