June 5, 2007

 

French food official says extensive research is the key to completely eliminate pig diseases

 

 

An aggressive approach to research is the key to avoid and eliminate diseases such as post-weaning multi-systemic wasting syndrome (PMWS), according to a French food safety official.

 

Francois Madec of France's Food Safety Agency told delegates at the Alltech Symposium, Lexington, Kentucky that additional research are needed to bring light on the causes of PMWS.

 

Madec believes PMWS are largely related to herd management such as breeding and feeding strategies. Although there have been developments in research for the disease, collected information may have collateral and detrimental consequences, thus a coordinated approach is needed, he said.

 

Explaining how PMWS occurred, Madec said suddenness of outbreak was a common feature across the world as well-performing farrow-to-finish units, high losses suddenly occurred due to wasting in growing pigs without any perceivable premonitory clinical signs at any other stage of the herds.

 

He said there are five basic hypothesis of where PMWS came from.

 

First, PCV2 changed, so PMWS is induced by a new specific virulent strain. Second, PCV2 didn't change, but there is another new or presently unknown pathogen involved.

 

Third, pigs were exposed to something new of a non-infectious nature, but which triggered PCV2 replication through immunomodulation and/or modification of the virus environment within the target cells. This new factor has been spreading through trade.

 

Fourth, management and husbandry have been changing and these changes in breeding herds may have also interfered with the routes of PCV2 spread. And finally, the genetic background of pigs changed, through reduced variability as a result of targeted breeding programmes and increased susceptibility of certain lines.

 

Madec said hypotheses one and two are supposed pathogen has only spread in countries where PMWS occurred. However, sudden onset is more compatible with hypothesis three, such an exposure would break the pre-existing more or less fragile balance involving PCV2.

 

He said the quantitative clinical expression of PMWS, depending on farm and also on the batch in farrow-to-finish systems, is most in favour of hypothesis four. Madec notes the immune system is affected in this disease and poor hygiene as well as poor housing and husbandry contribute to the burden of secondary pathogens.

 

But the most probable scenario in PMWS emergence still remains to be established, despite most of the pieces of the puzzle now being in place. That PCV2 plays a pivotal role is agreed, but the crucial question is why PCV2 suddenly became so influential on health.

 

Madec said PMWS as a clinical disease at both herd and pig level is a yes-or-no phenomenon as PCV2 is a necessary condition that is to be recognised in different stages.