“…The minimum protective SN titer was set as low as 1:10 or as high as 1:96 in serologic studies (Larson, 1996; McCaw et al , 1998; Tizard and Ni, 1998; Coyne et al , 2001 b ; Gaskell et al , 2002). Several studies found that 70–100% of client-owned or isolated research animals maintained protective titers for at least 3 years (Piercy, 1961; Prydie, 1966; Robson, 1966; Olson et al , 1988, 1997; Twark and Dodds, 2000; Abdelmagid et al , 2004; Bohm et al , 2004; Gill et al , 2004; Gore et al , 2005; Ottiger et al , 2006). Others suggest that many animals may not be protected after 2 years (McCaw et al , 1998; Jozwik et al , 2004).…”