These are gut-borne viruses, host specific to the pig, that are included in the group called “SMEDI viruses”. SMEDI stands for Stillbirth, Mummification, Embryonic Death and Infertility. The term is now also commonly used for parvovirus infection. Although these groups of viruses are distinct from that of parvovirus, they are often all grouped together clinically because the signs are similar. The enteroviruses are subdivided into serotypes of which at least 11 are known. Four of these, serotypes 1, 3, 6 and 8, have been implicated in reproductive problems in pigs. Serotype 1 is the Teschen/Talfan virus which can also cause paralysis in pigs. Usually, each pig herd has an array of different serotypes which circulate in weaned and young growing pigs sub-clinically. The pigs are protected by circulatory antibodies derived from their dam’s colostrum. By the time they reach breeding age they are solidly immune.
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.
Symptoms
Sows
- Embryo mortality.
- Mummification.
- Stillbirths.
- In some cases infertility associated with absorption of embryos also occur. (Repeats).
- 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.
- Paralysis.
- No symptoms in the adult breeding female.
Piglets, Weaners & Growers
- None.
Causes / Contributing factors
- Introduction of a new strain of virus into the herd.
- Poor gilt acclimatisation.
- Virus in semen.
Diagnosis
This is carried out by serology and virus isolation.
The symptoms of SMEDI can be mistaken for other causes. These include AD, Leptospirosis, PPV and PRRS