Key result
Feeding milk from scrapie-affected goats to new-born lambs resulted in scrapie infection in all 12 lambs that received large volumes (38-87 liters), confirming that the scrapie agent is present in goat milk and can transmit to susceptible species.
The scrapie agent is present in the milk of infected goats and can transmit the disease to susceptible species even at early preclinical stages.
Goat milk from scrapie-affected animals transmits to lambs at higher volumes; extends sheep data but leaves open goat-to-goat risk and field relevance.
BACKGROUND: Previous studies confirmed that classical scrapie can be transmitted via milk in sheep. The current study aimed to investigate whether scrapie can also be transmitted via goat milk using in vivo (new-born lambs fed milk from scrapie-affected goats due to the unavailability of goat kids from guaranteed scrapie-free herds) and in vitro methods (serial protein misfolding cyclic amplification [sPMCA] on milk samples). RESULTS: In an initial pilot study, new-born lambs of two different prion protein gene (PRNP) genotypes (six VRQ/VRQ and five ARQ/ARQ) were orally challenged with 5 g brain homogenate from two scrapie-affected goats to determine susceptibility of sheep to goat scrapie. All sheep challenged with goat scrapie brain became infected based on the immunohistochemical detection of disease-associated PrP (PrP(sc)) in lymphoid tissue, with an ARQ/ARQ sheep being the first to succumb. Subsequent feeding of milk to eight pairs of new-born ARQ/ARQ lambs, with each pair receiving milk from a different scrapie-affected goat, resulted in scrapie in the six pairs that received the largest volume of milk (38-87 litres per lamb), whereas two pairs fed 8-9 litres per lamb, and an environmental control group raised on sheep milk from healthy ewes, did not show evidence of infection when culled at up to 1882 days of age. Infection in those 12 milk recipients occurred regardless of the clinical status, PrP(sc) distribution, caprine arthritis-encephalitis virus infection status and PRNP polymorphisms at codon 142 (II or IM) of the donor goats, but survival time was influenced by PRNP polymorphisms at codon 141. Serial PMCA applied to a total of 32 milk samples (four each from the eight donor goats collected throughout lactation) detected PrP(sc) in one sample each from two goats. CONCLUSIONS: The scrapie agent was present in the milk from infected goats and was able to transmit to susceptible species even at early preclinical stage of infection, when PrP(sc) was undetectable in the brain of the donor goats. Serial PMCA as a PrP(sc) detection method to assess the risk of scrapie transmission via milk in goats proved inefficient compared to the bioassay.
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Konold et al. (2016) studied Scrapie (n=32). Milk from scrapie-affected goats vs. Sheep milk from healthy ewes (environmental controls) was evaluated on Scrapie infection confirmed by immunohistochemical detection of PrPsc. Feeding milk from scrapie-affected goats to new-born lambs resulted in scrapie infection in all 12 lambs that received large volumes (38-87 liters), confirming that the scrapie agent is present in goat milk and can transmit to susceptible species.
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