If you are producing PRRSV negative piglets at weaning from PRRS vaccinated sow herd but they are transferred to a PRRS positive finishing site (with PRRS related respiratory symptoms) at 40kgs, would it be sensible to vaccinate these piglets at weaning? Based on Lars Erik Larsen opinion, there are two different options to approach this situation: 1. Vaccinate the pigs at... read more test →
Length of the quarantine: When we want to introduce negative replacements to a PRRS positive farm, the quarantine, or acclimation rather, must be long. "Long" meaning a period of not less than 2 months, because during this period our intention is to infect the new arrivals, giving them time to recover from the infection and lose their status as virus shedders before introducing them into the farm and starting to... read more test →
Monitoring programs will differ depending on whether they are to be applied to a farm, an area, or a country, but I understand that in this case we are referring to a farm. The program will vary depending on the type of farm and its disease status. In the case of the PRRS, five possible statuses have been described: What sample and technique should we use to check... read more test →
Attenuated PRRS vaccines (Modified Live Vaccines) are not designed to pass immunity to the piglets, although they will. How do naïve animals response to PRRS vaccines? PRRS live attenuated vaccines do not produce high levels of circulating antibodies (IgG), which we want to find present in the colostrum (humoral immunity). In PRRS-negative animals the PRRS vaccines produce a weak serological reaction, although it allows cellular immunity development sufficient to... read more test →
This is quite a difficult question to answer, as it depends of a wide range of factors, such as: Herd structure, herd size, herd organization, PRRS virus gilt acclimation strategies and the number of herds situated in the area (i.e. how high the PRRSV infection risk is). Sow vaccination programmes against PRRS virus In a previous question answered by Enric Marco on this site, the different possibilities of sow... read more test →
Could abortion or stillborn happen in sows less than three weeks before farrowing if they are given a PRRSv MLV vaccine? And what can be the consequences of vaccinating for PRRSv during late pregnancy (2-3 weeks before farrowing)? Because when blanket vaccination is applied in the farm, it sometimes falls three to two weeks before farrowing in some sows. To answer this question, a previous explanation of the pathogenesis of... read more test →
The inoculation of PRRS live virus from the farm as a method to acclimatise the gilts has been used extensively with positive results provided that: It can be done on isolation as not to disturb the stability of the farm. It can be done early enough to have at least some 6 weeks so the PRRS infection produced has the time to cool down. But keep in mind that it... read more test →
To answer this question, the first thing to be considered, it´s that it is not possible to differentiate, by a serum antibody test, an animal infected with PRRSv from a vaccinated one. Secondly, the pathogenesis of infection should be considered. Pathogenesis of PRRSv infection in boars An infected boar usually develops viremia (the presence of virus in blood) that normally lasts for a week or two. During this viremia... read more test →
To control an unstable PRRS situation, a farm did more than 4 times a PRRS mass vaccination with 2 different commercial NA type MLV (one commercial vaccine in one week, and the second vaccine the following week, by turns). After 8 weeks from first mass vaccination, they found high fever and stillborn (confirmed PRRSv positive by PCR). This kind of excessive PRRS vaccination to sows in less than 8 weeks... read more test →
The PCR technique is usually very sensitive and it detects very small amounts of PRRS virus in blood or other samples, but there are some limitations to the interpretation of the results. PCR technique limitations Firstly, I would want to make sure that the gilts are confirmed PRRS virus negative in the source herd before being transported. To detect a 10% prevalence level with a 95% confidence you... read more test →