March 2016

Associate Photo
Mark Rooney
Director, US Swine Business Unit
515.669.4446
mark.rooney@pahc.com
Dear Subscriber: Welcome to Phibro ProSM, a newsletter for professionals in the swine production industry. Six to eight times a year, we will send you this e-newsletter with helpful information designed to help improve your business.

MJPRRS® Technology: Actual Farm Scenario

There are many tools available through diagnostic laboratories to help classify PRRS viruses. This farm utilized many of these comparison methods to try to explain what was occurring in this particular population. The diagnostic laboratories confirmed genetically similar PRRS viruses, but the animals on this farm provided a dissimilar clinical picture with each of the identified occurrences.

History of this site suggested that PRRS was a regular event, occurring every 5 – 8 months with various presentation of clinical signs – PCR positive piglets, poor suckling and/or nursery performance, abortions and sick reproductive animals.

In December 2010 (Dec-10) this particular farm became PRRS positive with a virus identified as a 1-18-2 by Restriction Fragment Length Polymorphism (RFLP). As historically would be expected, in May of 2011 (May-11) PRRS was again identified with associated clinical signs however, this time the virus was identified as a 1-2-2 by RFLP. The May-11 virus and the Dec-10 virus were highly related (99.3% sequence similarity), further complicating the clinical experience that was occurring. In this scenario it was possible to equate the clinical differences with the change in RFLP. However, comparison of diagnostic information and presentation of clinical signs did not match clouding the overall analysis.

In December 2011 (Dec-11), only 7 months removed from the last clinical presentation, clinical signs were associated with PRRS virus identified by RFLP to the May-11 virus (99.3% similar, both 1-2-2). Given the close similarities in the virus sequences and RFLPs, the assumption would be that herd immunity should still exist and it would not be re-breaking with PRRS, however this was not the case. At this point the producer and veterinarian were thoroughly confused. Despite the viruses being similar by conventional diagnostics, clinically the pigs were indicating that this virus (Dec-11) was different from the last clinical presentation (May-11) which was also different from the clinical presentation before that (Dec-10).

The solution to this perplexing situation was to send these sequences to MJ Biologics (MJ) for analysis. There was a need to determine why the clinical presentation was different and why repeated clinical signs were occurring with genetically similar PRRS virus sequences. MJ identified the following Immune Groups for each of these viruses: Dec-11 (D-5), May-11 (D-4), and Dec-10 (D-4b). MJ reported that this farm, because of these three different immune groups, would likely have seen occurrences of clinical signs on the farm.


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Occasional PCR positive piglets, poor suckling piglets and/or nursery performance, some abortions and sick reproductive animals appeared mild in a January 2012 (Jan-12) break. The farm again identified a 1-18-2 virus which was not as highly related to any of the previous viruses identified. The Jan-12 virus was 93.0% similar to the Dec-11 virus, 92.5% similar to the May-11 virus, and 92.9% similar to the Dec-10 virus. Clinically, it was not difficult to identify that changes had occurred with this particular PRRS virus identification. Despite having matched RFLP (1-18-2) with the Dec-10 PRRS clinical presentation, all areas of production behaved as if this virus was completely foreign to them. The Jan-12 virus was confirmed through sequence analysis using the MJPRRS Grouping Technology as a D-6, a completely new immune presentation.

Not only was this a new immune presentation (D-6), but this virus also was differentiated from the original on-farm virus by nucleotide and amino acid sequence comparisons making this a likely new virus introduction. This virus was further identified with a 100% PRRS virus ORF 5 sequence match to a very close neighbor and thus the virus was considered a new introduction unrelated to the originally identified virus.

Nearly 12 months later in December 2012 (Dec-12), PRRS virus was identified in suckling piglets. This virus was again identified as a 1-2-2 and highly related to the Dec-10 (98.7% similar), May-11 (99.3% similar) and Dec-11 (99.7% similar) viruses. It is likely that the Dec-12 virus originated from mutations of the Dec-10 virus as did the Dec-11 and May-11 viruses. Identification of expected clinical presentations, as determined by the MJPRRS Grouping Technology, helped to explain the internal dangers of PRRS virus mutations within a population.

The MJPRRS Grouping Technology was able to identify where changes would have been expected clinically in this population of animals. None of the other three methods (nucleotide homology comparisons, RFLP, or farm dendrogram) utilized in this comparison were able to consistently do so. In addition to their inability to predict clinical presentation, these methods also failed to determine in this case which set of signs were related to internal viral changes versus those arising from an external virus introduction. In our next issue we will discuss how we are able to utilize this information to create a Tailor-made® solution to this formerly intractable problem.

For additional information on how you can apply this analysis to your farm or farm system or to inquire about having your PRRS virus grouped free of charge, please contact your Phibro Animal Health Representative.

 

Potency and efficacy of autogenous biologics have not been established.
MJPRRS Autogenous Vaccines manufactured by and distributed to veterinarians by Phibro Animal Health Corporation.

HEALTHY ANIMALS. HEALTHY FOOD. HEALTHY WORLD.®

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