Andrea Ladinig – PRRSControl

In an outbreak of PRRS with clinical symptoms, are modified live vaccines recommended?

Andrea Ladinig — Mon, 19 Dec 2022 07:06:08 +0000

A swine vet consultant recommends not to use a PRRS live vaccine because the efficacy of the vaccine is not enough to control the field viruses. If there is an outbreak of PRRS with clinical symptoms, how long will it take to be a stable situation without vaccination? Or should we use a vaccine to make and keep a PRRS stable farm? PRRSV MLVs are not able to completely control infections, particularly not with heterologous field virus, so no sterile immunity is induced by the use of MLVs. However, hardly any vaccine will induce sterile immunity and prevent infection. The main goal of vaccines is to control clinical disease and reduce economic losses. These effects can also be achieved by PRRSV MLVs; those vaccines are able to reduce clinical signs both in sows/gilt and piglets, so they are able to reduce reproductive disorders and respiratory signs and improve growth performance. It could be demonstrated in the past that in addition to the use of MLVs, additional measures are necessary to reduce viral load in affected farms in order to control PRRS; experimental data has shown that vaccinated piglets are protected by field virus infection up to a certain infectious dose; […]

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Could we apply heterologous prime-boost vaccine strategies in controlling PRRS?

Andrea Ladinig — Thu, 14 Jul 2022 12:40:29 +0000

There was documented success using heterologous prime-boost vaccine strategies in controlling Influenza. Could we apply the same procedures/principles in PRRS? In theory heterologous prime boost vaccination might also be beneficial in case of PRRSV. However, it has to be kept in mind that currently mainly modified live virus (MLV) vaccines are used to combat PRRSV, since current inactivated vaccines often lack sufficient efficacy. When using more than one MLV in the same herd, precautions must be put in place to prevent the formation of chimeras between different vaccine viruses. The European medicines agency (EMA) recommends using not more than one vaccine virus strain within a herd and keep a withdrawal time, i.e. wait before introducing another MLV strain into the herd for as long as vaccinated animals might shed vaccine virus; this period is indicated by the manufacturer and varies between different PRRSV MLV products. If you want to know more about PRRS vaccination read out chapter: Vaccinology You can ask your own question! Visit Pig333.com and submit your question to the experts. Andrea LadinigUniversity of Veterinary Medicine, Vienna

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Is there any possibility of incursion and spreading of PRRSV through pork brought in by farmworkers?

Andrea Ladinig — Mon, 21 Mar 2022 09:37:14 +0000

Is there any possibility of incursion and spreading of PRRSV through pork? Should farmworkers avoid touching or bringing pork to the farm for PRRS prevention? The risk of spreading PRRSV through pork cannot be 100% excluded; however, the likelihood is very low. First, a comparatively high amount of virus would be needed to infect a pig with PRRSV through the oral route (1 x 105.3 TCID50) compared to parenteral exposure (≤20 particles can result in infection). Also, the probability of acute infection with high amounts of replicating virus being present is rather low in slaughter age pigs compared to younger piglets. Nevertheless, some pigs might bring PRRSV to the slaughterhouses. Target cells for PRRSV replication are cells of the monocytic lineage, mainly fully differentiated macrophages, while muscle cells are not susceptible to the virus. Therefore, resident virus that might be present in pork mainly results from residual infected blood not from infected myocytes. Therefore, rather low levels of virus can be expected in pork. The probability of survival of the virus will highly depend on pH value (while the virus is stable at pH 6.5 – 7.5, it will rapidly loose infectivity outside this range) and temperature (PRRSV […]

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Can the impact of PRRSv infection differ by age, gender or genetic line of pigs?

Andrea Ladinig — Mon, 01 Feb 2021 08:56:34 +0000

Can the susceptibility of PRRSV infection be different depending on the genetic line of pigs? Can the severity of the symptoms of PRRSV infection be different by age, gender, or genetic character? There are indeed differences in the genetic susceptibility of pigs towards PRRSV. Differences between pigs genetic lines Already in 1998 it has been demonstrated that certain breeds are less susceptible to PRRS than others; e.g. Meishan pigs had lower PRRS viral titers and less severe lesions than Duroc pigs (Halbur et al. 1998). Differences within pigs genetic lines The research investigating genetic susceptibility of pigs towards PRRSV done ever since has shown that also within the same genetic line there is quite some variation in the severity of disease. A single nucleotide polymorphism (SNP) has been identified on Sus scrofa chromosome 4 (SSC4) which is associated with weight gain and viral load in experimentally infected pigs (Boddicker et al. 2012, 2014a,b; Rowland et al. 2012; Schroyen et al. 2016). Receptor CD163 and PRRSV disease resistance The latest research dealing with PRRSV resistance of pigs focused on the receptor CD163 which is necessary to allow PRRSV to enter target cells. “Genetically modified pigs lacking […]

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Can we know if the replacement gilts are protected against PRRSv?

Andrea Ladinig — Fri, 15 Mar 2019 09:21:12 +0000

This is a very good question and the frustrating answer is: you cannot know for sure if animals are protected against PRRSv or not. There are no so called “correlates of protection” when it comes to PRRSv, so there is nothing we can measure in order to evaluate if an animal is protected. However, some diagnostic techniques do allow us to monitor the immunological status of the replacement animals against PRRSv. PRRSv diagnostics for replacement animals monitoring [youtube v=”IG4p7ONmLvs”] 1. ELISA Test In routine diagnostics, antibodies against PRRSv nucleoprotein are most often measured by ELISA techniques; those antibodies can confirm or exclude if an animal had contact to either PRRSv or a modified live virus vaccine. However, those antibodies clearly do not correlate with protection. Also, it cannot be distinguished if antibodies are directed against field virus or modified live virus from a vaccine. Also, those ELISA tests cannot distinguish between antibodies that were passively transferred to piglets via colostrum and antibodies that were actively built by the piglets´ immune system. 2. NA’s and cellular immune response measurement Other options to measure immune responses of pigs towards PRRSv include the measurement of neutralizing antibodies or cellular immune […]

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With a laboratory diagnostic positive to PCV2 and PRRS, how can we be sure which disease causes poor growth and respiratory distress?

Andrea Ladinig — Thu, 06 Sep 2018 14:02:51 +0000

I would recommend to include histologic investigation of lung and lymphatic tissues in the diagnostic work up. Histologic lesions can be quite indicative of the causative agent involved in the pathogenesis of disease. Also, in addition to routine H&E staining to evaluate lesions, specific staining techniques to identify pathogens – either at genomic or at protein level –within lesions can be performed like immunohistochemistry or in situ hybridisation. For the diagnostic work up of PCV2, a quantification of viral DNA should be performed since it is known that clinical disease is associated with viral burden. The detection of high viral load in several pigs is very indicative if there is involvement of PCV2 in the clinical problem. In addition, the selection of pigs for diagnostics is important and will influence results; selecting pigs early during the cause of infection might also help to identify which pathogen comes first and is the major player in a disease outbreak. Also, the use of vaccines to combat clinical disease due to viral infections might help identify the causative agent of the clinical problem on farm. Particularly, vaccines against PCV2 for piglets have proven to be very effective when used at the right time […]

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Reproductive and respiratory problems caused by PRRSV alone or in combination with Circovirus, App, Pasteurella, etc. are often seen in an endemic PRRS region. What would you advise in order to improve the situation?

Andrea Ladinig — Fri, 27 Jul 2018 11:29:07 +0000

In order to control clinical disease due to PRRSV infection -either with or without the combination of vaccines against PRRSV- it is essential to reduce virus introduction and circulation inside the herd. This can only be achieved through strict external and internal biosecurity protocols. For any herd (PRRSV positive or not), the introduction of new PRRSV strains has to be avoided. Routes of PRRSV transmission and introduction are well known and have been summarized amongst others by Cho and Dee 2006 (Cho and Dee, 2006). Biosecurity protocols to prohibit PRRSV introduction are fairly well understood and often in place. In contrast, the control of PRRSV circulation inside herds is often more difficult to accomplish. Critical animal groups are newly introduced animals or animals without protective immunity, e.g. gilts or weaned piglets after maternal immunity waned. Often, those animal groups keep up virus circulation inside the herd. The strict separation of those animal groups from other compartments of the farm by means of pig flow, separate personnel, clothing and boots, fomites, etc. can prohibit internal virus transmission. For gilts it is important to develop PRRSV immunity before first insemination since major reproductive problems due to PRRSV occur in early and late […]

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What is the status of Type I PRRS virus in Eastern Europe? Are strains becoming more pathogenic?

Andrea Ladinig — Tue, 17 Apr 2018 08:00:28 +0000

What is the current status of Type I PRRS virus in Europe, particularly Eastern Europe? Are strains continuing to become more pathogenic? Is there evidence of increased diversity of the PRRS ORF 5 virus? PRRSV, an RNA virus, has a high genetic diversity and continuously keeps evolving. By now, two separate species of PRRSV are recognized, PRRSV-1 (previously genotype 1 or EU genotype) and PRRS-2 (previously genotype 2 or US genotype). Both species have a high genetic diversity and particularly in Eastern Europe, a high diversity of PRRSV-1 isolates has been found. Changes in the genome can occur in each area of the genome; however, some areas are more consistent across different PRRSV isolates while other areas are more variable. ORF5 is one of the more variable regions in the PRRSV genome. That´s why it is often used for sequencing in order to characterize different virus isolates.The change in the genetic information of the virus does not necessarily implicate, that isolates are becoming more pathogenic. Indeed, we still don´t know the link between genetic background of a virus and it´s phenotypic presentation. Therefore, we cannot explain or predict pathogenicity of a particular PRRSV isolate based on its genetic background. A […]

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Can oral fluids ELISA test give false positive PRRS results if weaned piglets are fed with whey or plasma powder?

Andrea Ladinig — Tue, 29 Aug 2017 08:00:01 +0000

Experiences from experimental studies and the field have shown that ELISA tests for the detection of antibodies against porcine reproductive and respiratory syndrome virus (PRRSV) in oral fluid samples can give false positive results (Sattler et al. 2015; De Regge and Cay 2016). One possible explanation can be an exogenous source of PRRSV antibodies, for example included in the feed. The best described example is the use of spray-dried porcine plasma incorporated into the diet of nursery piglets which has been shown to cause false positive results in PRRSV oral fluid ELISA tests (Johnson et al. 2012). No reports on the use of whey in pig diets influencing the results of PRRSV oral fluid ELISA tests have been published. Feral and domestic swine represent the only known host of PRRSV (Zimmerman et al. 2012). Since cattle are not expected to support PRRSV replication or produce antibodies against the virus whey is a very unlikely exogenous source of PRRSV antibodies. If seemingly contradictory diagnostic results are obtained by oral fluid PRRSV ELISA tests, feedstuffs can be tested for the presence of exogenous PRRSV antibodies (Johnson et al. 2012). References: De Regge, N., Cay, B., 2016. Comparison of PRRSV Nucleic Acid and […]

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What’s the role of transport vehicles and loading bays to avoid PRRSV introduction into a farm?

Andrea Ladinig — Thu, 20 Apr 2017 08:00:02 +0000

There are several routes of PRRSV introduction into herds. Most common ways of PRRSV transmission within and between herds include infected pigs (Bierk et al., 2001) and contaminated semen (Yaeger et al., 1993; Christopher-Hennings et al., 2001); these are also called direct routes of transmission. In addition, PRRSV has been shown to be transmitted indirectly via contaminated fomites, personnel, or insects as well as through aerosols (Cho and Dee, 2006; Otake et al., 2010). Also, transport vehicles have been proven to act as mechanical vectors for PRRSV transmission (Dee et al. 2004). A group of American researchers led by Dr. Scott Dee has investigated different sanitation protocols for transport vehicles including a combination of disinfection and drying in order to prevent PRRSV introduction into herds through contaminated transport vehicles (Dee et al. 2005a; Dee et al. 2005b). Of course, preventing potentially PRRSV positive transport vehicles to access a farm area can reduce the risk of PRRSV introduction into herds. This is particularly true for “foreign” transporters, i.e. transporters that are not owned by the production unit and also transport pigs from other sources. One way to prevent transporters from approaching a farm might be the use of a loading bay […]

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