PLEASE REMEMBER TO SIGN UP TO THE DISEASE CHARTER WITH AHDB PORK.
When sourcing stock it is up to you to ask the breeder if they have suffered any diseases within their herd if you don’t ask you don’t know and the breeder will and should not be offended by your question as this shows due diligence on your behalf.
It it my intention to discuss diseases specific to the pregnant sow and the effects her infection will have on the unborn litter and then move on to respiratory disease, nervous system disease etc over the weeks. So hope you find it all helpful.
Reproduction Disease – Porcine Parvovirus (PPV)
Apart from a single very unusual report of skin disease in weaners, PPV is solely associated with the reproductive failure or with its effect on an unborn litter. Infection of the non-pregnant animal has no clinical effect and immunity is acquired that will be life-long and will protect all future litters. The effects that PPV infection will have on a pregnant sow depend on the stage of pregnancy, which I have shown below.
Stage of reproductive cycle Effect of PPV infection Result
Not pregnant No effect Immunity
At service and within Death of fertilised eggs/ Return to service 10 days of service differentiating embryos at 3 weeks 10 – 25 days post service Embryonic death Delayed return to service or small litter 25 – 75 days post-service Foetal death, often Variable-sized mummified progressive through the litter pigs affecting whole or part of the litter, and/or stillbornpigs
75 days plus Minimum effect on foetuses Possibly small pigs born as the immune response can be that have been checked during growth, and stillborn pigs
From this it can be seen that the effects of PPV infection can be stillbirth, mummification, embryonic death and infertility, giving the old acronym SMEDI. It should be noted that abortion is a very rare manifestation of PPV infection.
On a herd basis, in a naïve herd, an outbreak of PPV disease will last two to three months and will manifest by varying signs over that time in the following sequence:
- Increased regular returns to oestrus lasting two to three weeks
- Increased irregular returns to oestrus lasting two to three weeks simultaneously with above
- Stillborn pigs starting simultaneously with above for one to two months.
- Increase in mummified pigs from six to twelve weeks after (1) above, and failures to farrow.
- Drop in total litter size for two to three weeks from eighty days after the start of the outbreak.
It is a sequential disease, the classic sign of which is large numbers of mummified pigs within a litter, of variable size, starting around one month after an increase in returns to service. The diagnosis of PPV disease is based on clinical pictures supported by blood tests and by virus detection in the livers of mummified or stillborn pigs.
Prevention and Control
Highly effective vaccines against PPV, which we have discussed in the previous post on the group, are available and are given to gilts prior to breeding. The actual programme (number of doses and timing) varies between products, but it should be noted that maternally derived antibodies (those passed to a piglet in colostrums) can survive for up to six months and that these can block vaccine efficacy. Vaccination should, therefore, not be given too early in life. It is also worth noting that the disease can be transmitted from boars to sows or vice versa by direct mating with infected pigs or through artificial insemination from infected semen of boars.