Enric Mateu – PRRSControl

Can PRRS live vaccine elicit higher and faster immunity through Intradermal vaccination?

Enric Mateu — Wed, 21 Oct 2020 07:42:25 +0000

What kind of immunological benefit can we expect through ID route? The intradermal route is used in many vaccination protocols in humans and animals. The notion behind the use of this route is to take advantage of the excellent antigen presenting capabilities of dermal dendritic cells as well as to reduce the interference created by the presence of maternally-derived antibodies (MDA) in very well irrigated tissues (such as the muscle). In addition, the use of needleless devices for administering the vaccine improves animal welfare. Intramuscular & intradermal vaccination In the case of PRRSV vaccination it has been shown that the intradermal administration is at least equal to the intramuscular administration of live vaccines. In principle, intradermal administration does not result in a faster priming of the immune response. At present, there is no definitive evidence that with PRRSV intradermal vaccination there is less interference with the MDA. If you want to know more about the differences founded between intramuscular and intradermal vaccination, please visit our section Publications. You can ask your own question! Visit Pig333.com and submit your question to the experts. References A. Scollo et al., Livestock Science 233 (2020) 103939. Busquet, M. […]

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PRRSv MLV vaccine: Abortion or stillborn in sows less than 3 weeks before farrowing?

Enric Mateu — Fri, 25 Oct 2019 13:16:19 +0000

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 PRRSv-induced abortion is required. PRRSv vertical Transmission Abortion in PRRSv infection happens as a result of fetal infection (mainly) and damage to the placenta. The virus reaches the placenta during the viremic phase of the infection. To cross the placenta and to reach the fetuses it is needed that susceptible macrophages are present in there. Fig 1. PRRSv vertical transmission and its implications. Susceptible macrophages are not significantly present until the late gestation (around 80-90 days of gestation) and therefore, the PRRS virus is thought not being able to cross the placenta at least until day 86. Usually the PRRSv infects one of the fetuses in one uterine horn spreading afterwards fetus-to-fetus. Abortion happens on average between 10-14 days from the onset of the infection. This explains why […]

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Is it expected, for sows vaccinated with a MLV PRRS vaccine, to be all positive by ELISA test?

Enric Mateu — Thu, 17 Oct 2019 10:32:57 +0000

The answer to the question depends on whether it refers to naïve sows vaccinated against PRRS for the first time or to animals that have received multiple vaccinations with a MLV PRRS vaccine. Naïve sows vaccinated with MLV PRRS vaccine for the first time When naïve sows are vaccinated for the first time (modified live PRRS vaccine) about half of them seroconvert between 7-10 days after vaccination and by day 21 after vaccination all sows develop antibodies against PRRSV. ELISA values (optical densities or S/P ratios) may vary very much between animals. In contrast, when sows are multiple vaccinated with PRRS vaccines, a variable proportion of them may test negative by ELISA. Seroconversion of multivaccinated sows Moreover, in many animals already seropositive, re-vaccination with a PRRS vaccine does not produce a clear seroconversion in ELISA. It is worth to note, that by using different ELISA kits, the individual animals testing negative may be different. In other words, the ELISA used has influence in the result. In our experience, when animals are examined using several tests simultaneously, overall less than 5% of the vaccinated sows can be catalogued as real low or non-responders. Since ELISA results […]

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Can a PRRSv positive boar that has been vaccinated be used for artificial insemination?

Enric Mateu — Tue, 09 Jul 2019 08:22:25 +0000

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 period, the semen also contains the PRRS virus. From the second week, the shedding of the virus in semen can last several weeks. However, at this stage the presence of the virus in semen is intermittent, so an animal can be negative by PCR in semen one day but be positive at a later date. In addition, if a boar is vaccinated, the vaccine virus can also be shed in semen and reach females without immunity. Finally, it must be considered that a vaccinated animal could eventually become infected, although the probability is much lower than it would be if it had not been vaccinated. As a summary, PRRSv positive animals should not be used on a PRRS-free farm, even if they were vaccinated. If you want to learn […]

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Does the pathogenicity of PRRS virus depend on genotype? Does only NA type PRRS MLV can offer heterologous protection against both genotypes (NA and EU)?

Enric Mateu — Thu, 02 May 2019 10:49:31 +0000

In general, PRRSV2 strains (formerly North American type or genotype II) are more virulent than subtype 1 PRRSV1, that is, the formerly designated as genotype I isolates circulating in Western Europe. However, PRRSV1 isolates of other subtypes (2, 3 or 4) circulating in Eastern Europe can be of increased virulence. PRRSv virulent strains Additionally, some subtype 1 PRRSV1 isolates circulating in Italy or Belgium have shown the features of increased virulence. Moreover, while reproductive pathogenicity is more or less similar for all isolates (with some differences though), PRRSV2 isolates seem to be more pneumotropic than PRRSV1 (with exceptions again). So, if a scale of virulence was to be elaborated, the highly virulent Asian (Chinese) PRRSV2 isolates emerged in 2006 will be on top, followed by the highly pathogenic subtype 2 and 3 PRRSV1 of Eastern Europe, then the moderate virulence isolates of PRRSV2 and PRRSV1 followed by the less virulent isolates of any genotype. Heterologous protection The issue of heterologous protection is very different. There are many evidences indicating that some level of heterologous (interspecies) protection exists although this is limited and, again, in general of lesser magnitude than the intraspecific protection. Different papers indicated some […]

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Can the sows routinely vaccinated with PRRSV MLV transmit seroneutralizing antibodies to the offspring that can interfere with active immunity after vaccination with the same vaccine in early stages?

Enric Mateu — Mon, 15 Oct 2018 08:38:57 +0000

This a very complex question requiring a detailed answer. The development of neutralizing antibodies to PRRSV depends on several factors, among others the strain of the virus but also the idiosyncrasy of the pig. Attenuated strains usually produce less neutralizing antibodies than less attenuated ones but this cannot be precisely forecasted. Besides this, when the development of neutralizing antibodies is examined in a group of animals the diversity of titers can be high. An additional factor is that the neutralizing efficacy of the antibodies induced by one PPRSV strain against a different one cannot be forecasted neither. Maternally-derived antibodies will give the piglet some level of passive immunity against PRRSV although, again, this will vary based on the level of the immunity of the sow and the colostrum intake of the piglet. In summary, the offspring of well-immunized sows can be expected to have some levels of neutralizing antibodies against the PRRSV vaccine strain and, if the sows were infected by a wild-type strain, against the farm strain. To what extent those neutralizing antibodies will interfere is a matter of debate. Maternally derived antibodies & PRRSV vaccination According to Fablet et al. (2018) maternally-derived antibodies (MDA) impair piglets’ responses […]

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On a PRRS unstable farm with a mass vaccination (4 times/year) programme for PRRS and 3 times/year vaccination programme for Aujeszky´s disease, both for sows, we want to minimise stress due to vaccination, what do you recommend?

Enric Mateu — Thu, 28 Jun 2018 08:10:21 +0000

The vaccinations of pregnant sows are always difficult because of the possible side effects on the farrowing rate and prolificacy. For a good protection against PRRS and Aujeszky’s disease, a blanket vaccination with the aim of keeping the sow population as homogeneous as possible in terms of the protection against these two infections is ideal. My recommendation would be to try to use a combinable vaccine or administer both vaccines on the same day (in two different spots), so reducing the number of days of stress. Obviously, the election of vaccines that cause few reactions will be advisable. You can ask your own question! Visit Pig333.com and submit your question to the experts. In una scrofaia gestite in bande bi-settimanali, con scarsa portata al parto ha un programma vaccinale di 7 interventi: 4 di PRRS e 3 di Aujeszky, con vaccini vivi attenuati, non abbinabili tra loro. Si chiede, per poter minimizzare gli stress da vaccinazione quale opzione adottare: 1. cambiare il vaccino prrs per un vaccino abbinabile (già usato 3 anni fa) e ridurre gli interventi a 4 volte/anno; oppure, mantenere il programma vaccinale evitando la vaccinazione le periodo più critico (primi 30 giorni o 2 […]

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A PRRS positive Site I farm, that had reached stability, has suffered the disease again. What management should be carried out: close the farm and infect the sows again as it was done on the first occasion? At this moment, PRRS vaccine is not used.

Enric Mateu — Thu, 28 Jun 2018 06:20:37 +0000

First of all, I think the most convenient thing is to try to determine which were the causes that lead to infection being reactivated on the farm, because the situation is very different if the destabilization came due to an issue of internal management than if the situation arose due to a virus reintroduction from outside. If it could be that the virus had come from another infected farm -and this would be relatively easy to determine if the virus sequences were available- I think the first thing would be to conduct a systematic assessment of the external biosecurity measures of the farm and the possible errors that exist in it. If we do not do so, the virus will probably re-enter in the future since the same biosecurity gaps will continue to exist. In particular, replacement animal introduction protocols and the entrance procedures for transport and people, among other aspects, must be carefully evaluated. If, on the other hand, there is certainty that virus cannot have been introduced from another source, then the approach is different. In this case, what we must first determine is whether the approach is to eradicate the infection from the farm or merely stabilize […]

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In Vietnam, many farms vaccinate sows against PRRS but not piglets. Is there any risk to these farms? And, is there any risk if farms use type 1 PRRS live vaccine for sows and type 2 PRRS live vaccine for piglets or the opposite?

Enric Mateu — Mon, 18 Jun 2018 13:50:16 +0000

Vaccination of piglets is recommended when the farm is nearly stabilized or in small farms where one wishes to accelerate the stabilization. As far as the sow is farrowing piglets already infected at birth or if the virus is circulating at a high level in the farrowing rooms, vaccination of piglets is of no use since once the piglet is infected, the vaccine cannot increase the immunity of the pig. In other words, to vaccinate or not piglets is a matter of the dynamics of the infection in the farm. Certainly, if in site 1 piglets are not infected because they are the offspring of vaccinated sows and then are sent to infected nurseries or fattening units, vaccination could be considered to avoid problems. I do not see a reason for double vaccination with PRRSV1 and PRRSV2 vaccines except in the case of dual infection in the farm. If that happens, I would reconsider very seriously what biosecurity problems the farm has. You can ask your own question! Visit Pig333.com and submit your question to the experts. Enric MateuCentre for Research on Animal Health (CReSA), Barcelona University (UAB) – Spain

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What is measured by the ELISA tests?

Enric Mateu — Tue, 18 Jul 2017 08:00:14 +0000

Most animals infected with the porcine reproductive and respiratory syndrome virus (PRRS) develop antibodies in a 7 to 14 days range period from the start of infection; A small percentage – usually less than 5% – will develop those before day 21st. These initial antibodies are directed against the N protein of the virus, which is one of the most antigenic, but those antibodies do not have direct relationship with the protection since they are devoid of virus neutralization capacity. Most commercial ELISAs use this N protein for diagnosis as it allows a quite early detection. On the other hand, N protein shares epitopes that are common to type-1 and type-2 PRRS virus, allowing the ELISA based on this protein to be universal. Some commercial kits have added other antigens (eg GP5) in order to gain detection spectrum. Current ELISAs cannot differentiate between infected and vaccinated animals. Most PRRS ELISAs are based on a format known as indirect ELISA, although there are other types on the market. The indirect ELISA is based on attaching the virus antigen to the microtiter plates used to perform the test, and adding afterwards the serum sample to be tested. The reaction is usually revealed […]

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