Low-volume goat milk transmission of classical scrapie to lambs and goat kids

Authors: MADSEN-BOUTERSE, SALLY - Washington State University; Highland, Margaret; Dassanayake, Rohana; Zhuang, Dongyue; Schneider, David

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/6/2018
Publication Date: 9/20/2018
Citation: Madsen-Bouterse, S.A., Highland, M.A., Dassanayake, R.P., Zhuang, D., Schneider, D.A. 2018. Low-volume goat milk transmission of classical scrapie to lambs and goat kids. PLoS One. 13(9):e0204281. https://doi.org/10.1371/journal.pone.0204281.
DOI: https://doi.org/10.1371/journal.pone.0204281

Interpretive Summary: Classical scrapie is a prion disease that is highly transmissible to newborn lambs and goat kids. This fatal neurologic disease is a focus of eradication programs worldwide, the success of which depends on identifying all sources of infection. Classical scrapie prions can be shed in the milk of infected ewes such that transmission to lambs may occur after only a few days consumption. The milk from infected goats also poses a risk but this has only been tested in lambs consuming large volumes of milk over weeks of time. In the present study, transmission of classical scrapie to lambs and goat kids occurred even after only a few days consumption of milk from goats in the preclinical phase of classical scrapie infection. Thus, like sheep milk, even limited exposure to goat milk can pose a significant risk for scrapie transmission in lambs and in goat kids.

Technical Abstract: The risk of classical scrapie transmission in small ruminants is highest during the neonatal period with the placenta recognized as a significant source of infection. Milk has also been identified as a source of scrapie with sheep-to-sheep transmission occurring after neonatal consumption of as little as 1-2 liters of milk; concurrent mastitis due to small ruminant lentivirus (SRLV) infection may be associated with increased scrapie transmission via milk in sheep. In contrast, goat-to-sheep transmission has been documented only after prolonged consumption of >30 liters of milk. The goal of the current study was to assess transmission of scrapie to goat kids and lambs following low volume, short duration consumption of milk from infected goats. Milk from two does (female goats) with pre-clinical scrapie was fed to four goat kids (<4.5 L each) and four lambs (~3.7 L each) beginning ~24 hours after birth. Scrapie transmission was detected in three sheep as early as 18 months post inoculation; transmission was also detected in two goats but not until postmortem analyses at 33 months post inoculation. Each milk donor goat also had naturally-acquired infection with SRLV. Different degrees of lymphohistiocytic inflammation and PrP-Sc accumulation were observed in mammary gland tissues of the donors, which appeared to associate with transmission of scrapie via milk. Thus, similar to the risks of milk transmission of scrapie from sheep, even limited exposure to milk from goats can pose significant risk for scrapie transmission to both goat kids and lambs.