Infection is via the faeco-oral route or the venereal route and transmission is due to introduction of live pigs with the disease or infected semen or ova. Lateral spread may also occur in younger pigs. Sows may remain carriers of the disease for many months and pass this on to up to 10% of their progeny. | Infection is via the faeco-oral route or the venereal route and transmission is due to introduction of live pigs with the disease or infected semen or ova. Lateral spread may also occur in younger pigs. Sows may remain carriers of the disease for many months and pass this on to up to 10% of their progeny. |