Reproductive problems only occur when a new serotype, to which the gilts are not immune, enters the herd and multiplies in the breeding females. This probably does not happen very often.

It is interesting to note that since the introduction of parvovirus vaccine and the excellent results achieved, the effects from SMEDI viruses would appear to be almost non existent, suggesting that this group of viruses are not important as a cause of reproductive failure.

Clinical signs
Natural infection of enteroviruses takes place by mouth through the ingestion of infected faeces. They multiply in the small and large intestines and in the absence of circulating antibodies escape from the intestine into the blood streams to the uterus. They cross the placenta, to produce the typical symptoms of embryo mortality, mummification and stillbirths. In some cases infertility associated with absorption of embryos also occur. If reproductive failure results there will be increases in embryo mortality, foetal deaths and mummified and stillborn piglets. Infection and disease only occur in non-immune sero-negative animals.

Diagnosis
This is carried out by serology and virus isolation.

Similar diseases
SMEDI can be confused with PPV and PRRS infection and occasionally with AD and leptospirosis.

Treatment

• There is no treatment but if a herd experiences problems with enteroviruses in incoming gilts, management practices should ensure that gilts are exposed to infection at least six weeks before breeding. See acclimatisation chapter 5.