Chronic Wasting Disease (CWD)

APPENDIX 2

Chronic Wasting Disease (CWD) Disease Name: • Chronic wasting disease (CWD), a TSE of deer and elk Disease Agent: Priority Level: • Chronic Wasting Disease (CWD) prion • Scientific/Epidemiologic evidence regarding blood Disease Agent Characteristics: safety: Theoretical • Public perception and/or regulatory concern regard- • Current evidence supports the theory that the infec- ing blood safety: Very low tious agent is a prion. However, the existence of • Public concerns regarding disease agent: accessory factors has not been excluded. Low/Moderate • Prions are considered members of the transmissible spongiform encephalopathy (TSE) group of agents Background: that include kuru, Creutzfeldt–Jakob Disease (CJD) and variant CJD (vCJD); both CJD and vCJD are dis- • CWD was previously thought to be limited to cussed in separate fact sheets. Prion diseases are endemic areas in northeast Colorado, southeast either sporadic, inherited, or infectious. Prions are Wyoming, and southwest Nebraska. However, it the agent, whether heritable through a germline has recently been found in the wild in several mutation in the human gene, PRNP, or infectious. new areas in North America. It is also found in com- • Prions are infectious proteins that are devoid of mercial game farms in several states and Canadian nucleic acid that result in certain disorders through provinces. binding and accumulation of the abnormal disease- • The origin of CWD is unclear but it appears to have causing prion isoform to the normal prion protein. emerged only a couple of decades ago in the wild. • Mammalian prions replicate by recruiting the normal Transmission to other species in the wild or to cellular isoform of the prion protein PrPC to form a humans has not been reported. disease-causing isoform designated PrPSc.PrPSc or • A recent study showed that it could be experi- PrPres are the designations for the pathogenic forms mentally transmitted to calves by direct intracerebral and are used interchangeably in the literature. inoculation. • Prions are nonimmunogenic as a result of the sharing • Recent investigation of cases of classical Creutzfeldt– of epitopes with the normal cellular isoform. Jakob Disease (CJD) in deer hunters showed no epi- •PrPC is soluble and circulates in plasma, is also demiologic link with CWD. present on many cell membranes, and has a molecu- Common Human Exposure Routes: lar weight of about 33-35 kDa. •PrPSc has a more restricted tissue range than does • No known transmission to humans, but exposure PrPC. could occur through handling or consuming deer and • Prion diseases represent disorders of protein confor- elk. A recent study found that the CWD prion might mation in which the tertiary structure of the precur- be present in meat from infected animals. sor protein is profoundly altered. The transition Likelihood of Secondary Transmission: occurs when the a helical protein of PrPC changes into a b-sheet-rich molecule of PrPSc.PrPSc or PrPres is • Unknown, not reported folded into a form containing 50% b sheet and is resis- At-Risk Populations: tant to proteases (proteinase K, lysosomal enzymes). •PrPSc can form aggregates that precipitate as amyloid • In theory only: hunters, meat processors, taxider- plaques in the CNS; these are a histopatho- mists, and those who consume deer or elk meat logical hallmark of the transmissible spongiform Vector and Reservoir Involved: encephalopathies. • Physicochemical properties: Resistance of prions to • Reservoir is infected deer and elk commonly used disinfectants (formaldehyde, glut- Blood Phase: araldehyde, ethanol, and iodine) is well recognized. Immersion in undiluted bleach (60,000 ppm or mg/L • Unknown of available chlorine) for 1 hour is only partially effec- Survival/Persistence in Blood Products: tive. Prions are resistant to ultraviolet light and ioniz- ing radiation, ultrasonication, nucleases, boiling, and • Unknown heat. High concentrations of NaOH (1-2 N) and pro- Transmission by Blood Transfusion: longed autoclaving (1-5 h) at high temperatures (120- 135°C) are advocated for disinfection. • Unknown

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Cases/Frequency in Population: Impact on Availability:

• No human case of the disease has ever been • Agent-specific screening question(s): Not applicable; confirmed. would be significant if required given the popularity • CWD in 15% of cervids in affected areas of hunting in the population • Laboratory test(s) available: Not applicable Incubation Period: Impact on Blood Safety: • Difficult to determine in natural infection; experi- mentally, 1-2 years • Agent-specific screening question(s): Not applicable • Laboratory test(s) available: Not applicable Likelihood of Clinical Disease: Leukoreduction Efficacy: • Unknown in humans • Unknown, but probably limited by analogy with other Primary Disease Symptoms: TSEs • Not applicable in humans Pathogen Reduction Efficacy for Plasma Derivatives: • Wasting, ataxia, tremors in infected animals • Inactivation data not available. Highly significant Severity of Clinical Disease: dilution and/or partitioning of infectivity away from final derivatives by fractionation process suggested in • High among dear and elk (progressive, invariably animal models using other prion agents. fatal) Suggested Reading: Mortality: 1. Angers RC, Browning SR, Seward TS, Sigurdson CJ, • 100% for symptomatic disease Miller MW, Hoover EA, Telling GC. Prions in skeletal Chronic Carriage: muscles of deer with chronic wasting disease. Science 2006;311:1117. • Unknown 2. Chronic Wasting Disease Alliance. [cited May 2009]. Treatment Available/Efficacious Available from: http://www.cwd-info.org/ 3. Hamir AN, Kunkle RA, Miller JM, Greenlee JJ, Richt JA. • Not applicable Experimental second passage of chronic wasting mule deer Agent-Specific Screening Question(s): disease (CWD ) agent to cattle. J Comp Pathol 2006;134:63-9. • No specific question is in use. 4. Kim TY, Shon HJ, Joo YS, Mun UK, Kang KS, Lee YS. • Not indicated because of the absence of recognized Additional cases of chronic wasting disease in human infection. imported deer in Korea. J Vet Med Sci 2005;67:753-9. • No sensitive or specific question is feasible. If risk to 5. Mathiason CK, Powers JG, Dahmes SJ, Osborn DA, humans is confirmed and route of transmission is Miller KV,Warren RJ, Mason GL, Hays SA, Hayes-Klug identified, exposure to deer and elk (e.g., hunting, J, Seelig DM, Wild MA, Wolfe LL, Spraker TR, Miller meat consumption) could be evaluated as a screening MW, Sigurdson CJ, Telling GC, Hoover EA. Infectious question. prions in the saliva and blood of deer with chronic wasting disease. Science 2006;314:133-6. Laboratory Test(s) Available: 6. Xie Z, O’Rourke KI, Dong Z, Jenny AL, Langenberg JA, • No FDA-licensed blood donor screening test exists. Belay ED, Schonberger LB, Petersen RB, Zou W, Kong • No presymptomatic test is available. Q, Gambetti P, Chen SG. Chronic wasting disease of elk and deer and Creutzfeldt–Jakob disease: compara- Currently Recommended Donor Deferral Period: tive analysis of the scrapie prion protein. J Biol Chem • No FDA Guidance or AABB Standard exists. 2006;281:4199-206.

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