PRNP and prion disease: To do so, fly food was supplemented with scrapie-infected sheep brain homogenate to allow oral exposure of VRQ ovine PrP Drosophila larvae to ovine prions (Thackray et al. 2012a), which mimicked what is considered to be the natural route of prion infection in most cases of transmissible mammalian prion disease (Glatzel and Aguzzi 2000; Mabbott and MacPherson 2006), including classical scrapie of sheep (van Keulen et al. 2008).