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Weekly Overview: Progress on PRRS and Other Pig Health Issues

13 May 2013

GLOBAL - Porcine Reproductive and Respiratory Syndrome (PRRS) is among the world's most costly pig diseases and it is proving challenging to control, particularly because of the different viral strains that exist. New research sheds some light on how the strains impact the pig's immune system in different ways. Hungary has been declared free of Classical Swine Fever and in the US, a new Bill will further tighten up on antibiotic use in animal agriculture.

Porcine Reproductive and Respiratory Syndrome (PRRS) is proving to be a challenging disease to bring under control – and very costly to the industry.

A recent study from the US puts the annual cost there at US$664 million – more than in 2005 and with a greater share of this cost in the breeding herd as some progress has been made in controlling the disease in growing pigs.

The US National Pork Board in the US has suggests that, by developing a better understanding of the mechanisms PRRS virus uses to evade the immune system, scientists will be in a much better position to deal with the infection,

The syndrome affects the reproductive performance of breeding sows and slows growth rates among grower pigs and is considered the most costly disease facing North American pork producers.

Several strategies have been used to address PRRS including the establishment of more than two dozen regional PRRS elimination projects across the US.

The Board’s Dr Lisa Becton acknowledges it is hard to know exact numbers but many farms see recurring issues with PRRS - both in terms of new outbreaks and the recurrence of the disease on farms that had previously been affected.

She highlights that we do not yet fully understand the mechanism that the virus uses to evade the pig’s immune system, which is one reason why vaccinating against one strain of the virus does not confer complete or absolute protection against any other strain.

New research from Spain may help to shed some light on these issues. Researchers of CReSA have demonstrated that inoculation with different PRRS virus strains result in different virological and immunological outcomes and in different degrees of homologous and heterologous protection.

Their results indicate that almost opposite models of immune response to the virus could exist, depending on the strain: one based mainly in the development of neutralising antibodies (NA) with low virus-specific interferon-γ secreting cell (IFN-γ-SC) responses, the other with predominance of IFN-γ responses and a poor development of NA.

In virological terms - but not based on zootechnical parameters - heterologous immunity sometimes could be more efficacious than the homologous one, the CReSA research team added.

EU Member States have voted to remove the remaining health restrictions for classical swine fever (CSF) in wild boar in Hungary. Surveillance carried out in 2012 and early 2013 has shown that the disease has been eradicated.

Finally, in health-related news, three US senators have introduced the bipartisan Antimicrobial Data Collection Bill, which aims to increase the data collected by the FDA on antibiotic use in farm animals. The news has been applauded by Pew Charitable Trusts as a move towards ending antibiotic use for growth promotion.

Jackie Linden

Jackie Linden

Top image via Shutterstock

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