The “normal” sporadic and unexplained abortion rate in pigs is approximately 1 to 2 % of pigs that are mated and achieve a pregnancy. The routes of infection of pig foetuses by abortogenic agents such as viruses and bacteria are usually via the bloodstream following an initial septicaemia – this pattern is not different to other livestock, but of course there are more foetal piglets that may be exposed, compared to lambs or calves