Indirect transmission of Actinobacillus pleuropneumoniae

orcine pleuropneumonia is caused by Actinobacillus pleuropneumoniae. This organism is thought to be transmitted mainly through direct contact, usually after asymptomatic carrier pigs are introduced into a herd. The possibility of indirect transmission has only occasionally been raised.1,2 Nicolet reported that the source of infection in Swiss specific-pathogen-free (SPF) herds was often unknown, and that in an experimental infection, some pigs were accidentally infected through contaminated boots, clothes, or equipment.1 The source of infection in a Danish SPF herd also could not be identified.2 However, since most recent reports have failed to specifically address the possibility that A. pleuropneumoniae can be transmitted indirectly, it remains an open question.