Evidence for the transmission of scrapie to sheep and goats from a vaccineagainst Mycoplasma agalactiae

An accidental infection from a vaccine was suggested as the explanation for the sudden increase in outbreaks of scrapie in Italy in 1997 and 1998. Thi s paper describes a recent outbreak of scrapie in sheep and goats which wer e exposed to the same vaccine. Ho ewes or goats had been imported into the herd since 1992, but a vaccine against Mycoplasma agalactiae had been admin istered twice, in 1995 and 1997. High rates of crude mortality and scrapie incidence were experienced by both species, all birth cohorts were involved and a large proportion of aged animals was affected. A pattern of brain le sions was observed, with slight differences between the sheep and goats, wh ich was very similar to the pattern observed in animals previously exposed to the same vaccine but clearly different from that observed in the brains of sheep with scrapie in a flock not exposed to the vaccine. Regardless of their exposure status, genotype analysis of the sheep showed the presence o f polymorphism only at codon 171. The patterns of both incidence and brain lesions provide evidence that the epidemic of scrapie was due to the use of the vaccine.