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ARS Home » Midwest Area » Ames, Iowa » National Animal Disease Center » Virus and Prion Research » Research » Publications at this Location » Publication #199994
Title: Experimental transmission of scrapie agent to susceptible sheep by intralingual and intracerebral inoculation

Author
item Hamir, Amirali
item Kunkle, Robert
item BULGIN, MARIE - UNIVERSITY OF IDAHO
item ROHWER, ROBERT - UNIVERSITY OF MARYLAND
item GREGORI, LUISA - UNIVERSITY OF MARYLAND
item Richt, Juergen

Submitted to: Canadian Journal of Veterinary Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/25/2007
Publication Date: 1/1/2008
Citation: Hamir, A.N., Kunkle, R.A., Bulgin, M.S., Rohwer, R.G., Gregori, L., Richt, J.A. 2008. Experimental transmission of scrapie agent to susceptible sheep by intralingual and intracerebral inoculation. Canadian Journal of Veterinary Research. 72:63-67.

Interpretive Summary: Scrapie, a transmissible spongiform encephalopathy (TSE), is a naturally occurring fatal disease of sheep and goats. In this study, Suffolk lambs were inoculated with the scrapie agent by two different routes (in the tongue and in the brain). Inoculated animals were euthanized when advanced clinical signs of scrapie were observed. In both groups of sheep, lesions of scrapie and the presence of scrapie agent was demonstrated. Brain-inoculated sheep had a mean survival time of 17.6 months, whereas the tongue-inoculated animals had a slightly longer mean incubation time of 18.3 months. Since the former method of inoculation is associated with occasional risks to the recipient animals (such as anesthesia-induced complications, brain hemorrhage and infections), and the tongue inoculation was very efficient, it may be more humane to utilize the tongue inoculation method for TSE transmission studies. However, before this method can be recommended, more research needs to be done to show that other TSE agents would be able to transmit disease via the tongue as shown for scrapie in sheep.

Technical Abstract: Scrapie, a transmissible spongiform encephalopathy (TSE), is a naturally occurring fatal neurodegenerative disease of sheep and goats. This study documents incubation periods, pathological findings and distribution of abnormal prion proteins (PrP**res) by immunohistochemistry in tissues of genetically susceptible sheep inoculated with a pool of US sheep scrapie agent. Four-month-old Suffolk lambs (AA/RR/QQ at codons 136, 154, and 171, respectively) were inoculated by two different routes (intralingual and intracerebral) with an inoculum consisting of a pool of scrapie-affected sheep brains. Inoculated animals were euthanized when advanced clinical signs of scrapie were observed. Spongiform lesions in the brains and PrP**res deposits in central nervous system (CNS) and lymphoid tissues were present in all sheep with clinical prion disease. Intracerebrally inoculated sheep had a mean survival time of 17.6 months, whereas the intralingually inoculated animals had a slightly longer mean incubation time of 18.3 months. Since the intracerebral method is associated with occasional risks to the recipient animals (such as anesthesia-induced complications, intracranial hematoma and CNS infections), and the intralingual replication was very efficient, it may be more humane to utilize the intralingual method for TSE inoculations of sheep. However, before this method can be recommended, more research needs to be done to show that other TSE agents would be able to transmit disease via the tongue as shown for scrapie in sheep.