Table 1. Assessing zoonotic potential of TSE agents.

		BSE	Scrapie	CWD
Overexpressing human PrP transgenic mice	+	+ [62, 69]	+ [56]	+ [70]	-
Gene targeted human PrP transgenic mice	+	− [22]	ND	− [57]	-
Transmission to primates	+	+ [63, 64]	+ [65]	+ [66, 71]	-
In vitro conversion assays using humanised substrate	+	+ [60, 61]	− [60]	+ [60]	-
Likelihood of zoonotic transmission	Likely	Yes	?	?	Unlikely

There are a number of different ways in which to assess zoonotic potential. Using a combination of evidence from both surveillance and research using in vivo and in vitro studies gives the best indication of the likelihood of zoonotic transmission. As shown in this table, if all studies give positive (+) results this could be taken as an indication that the risk of zoonotic transmission is high or likely. In contrast, all negative (−) results would indicate that the risk of zoonotic transmission is low or unlikely. Abbreviations: BSE, Bovine Spongiform Encephalopathy; CWD, Chronic Wasting Disease; ND, not done