If sows are vaccinated with a killed vaccine 20 days pre-farrowing, will stability in sows and piglets at nursery be increased? Would vaccination of piglets with a live vaccine be a better option?

Hjem Viden If sows are vaccinated with a killed vaccine 20 days pre-farrowing, will stability in sows and piglets at nursery be increased? Would vaccination of piglets with a live vaccine be a better option?

If sows are vaccinated with a killed vaccine 20 days pre-farrowing, will stability in sows and piglets at nursery be increased? Would vaccination of piglets with a live vaccine be a better option?

Answered by: Enric Mateu   I   Published on: June 16, 2016

In a farrow-to-finish farm with 650 sows and a 3-week batch farrowing system, blanket intradermal vaccination with a live PRRS vaccine is carried out every 3.5 months. PRRSv recirculation is present (PCR-positive animals at nursery of about 65 days of age). If sows were vaccinated with a killed vaccine 20 days pre-farrowing, would stability in sows and piglets at nursery be increased? Would vaccination of piglets with a live vaccine be a better option?

The answer to this question requires additional data. The question relates to a farrow-to-finish farm with positive PCR results in 65-day-old pigs. The presence of the virus in two-month-old animals may be compatible with an endemic cycle in nurseries with no infection in farrowing rooms, with an endemic cycle in nurseries from where the virus may go back to the farrowing rooms, or even with a low frequency of viraemic piglets in the farrowing roomsdue toinstability on the farm. The answer is different for each of those scenarios.

My suggestion in that case is, first of all, to determine precisely the status of the farm by sampling 30 piglets at weaning, and also sampling mid and late nursery pigs, and using PCR to examine the samples. If infection is already present in the farrowing rooms, the origin of the problem is either the birth of viraemic pigs (in which case your sows’ management needs to be revised, namely, vaccination protocol, husbandry and management of the sow herd as well as internal biosecurity) or thebackflow of viruses from the nursery (which would point to deficient internal biosecurity).

Discrimination between both situations could be done by, for example, sampling and testing piglets shortly after birth (focusing on weak piglets can be adequate in this case). If the problem is the birth of viraemic pigs, then additional vaccination will probably be of little help. If the problem is the backflow of virus, an additional vaccination before farrowing could help booster colostral immunity. The problem here is that the neutralising power of the antibodies against a specific strain cannot be forecast beforehand. This can be testedin vitro or, even better, by means of a field trial: keeping a group of sows as controls and vaccinating another batch and then sampling their offspring at different ages to determine the time of infection.

If the problem is an endemic cycle in nurseries with stable sows, my first suggestion would be to depopulate nurseries. If that is not feasible, then additional vaccination of sows before farrowing could help to some extent but, again,the magnitude of the effect cannot be forecast.

Increasing colostral immunity will increase the titres of neutralizing antibodies in piglets, and will certainly delay the fade-out of passive immunity, but you cannot be certain whether those antibodies will be effective against your circulating PRRSV strain or not. Again, if you choose this option, a trial and monitoring of piglets will need to be carried out.

 

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